Microbes in Human Welfare

Topic: Industrial and Household Uses of Microbes; Subtopic: Microbes in Domestic Products

Keyword Definitions:

• Aspergillus niger: A fungus used for industrial production of citric acid, not for household fermentation.

• Lactobacillus: A bacterium that converts milk into curd and improves gut health.

• Trichoderma polysporum: A fungus used for producing immunosuppressive drug cyclosporin A.

• Saccharomyces cerevisiae: Commonly known as baker’s yeast, used in baking and brewing.

• Propionibacterium sharmanii: Used in cheese production, particularly Swiss cheese.

Lead Question - 2025
Which of the following microbes is NOT involved in the preparation of household products?
A. Aspergillus niger
B. Lactobacillus
C. Trichoderma polysporum
D. Saccharomyces cerevisiae
E. Propionibacterium sharmanii
Choose the correct answer from the options given below:
(1) A and B only
(2) A and C only
(3) C and D only
(4) C and E only

Explanation: The correct answer is (2) A and C only. Aspergillus niger is used industrially for citric acid production, and Trichoderma polysporum produces cyclosporin A, an immunosuppressive drug. Both are not part of common household fermentation processes. In contrast, Lactobacillus, Saccharomyces cerevisiae, and Propionibacterium sharmanii are regularly used in preparing curd, bread, beer, and cheese at home.

1. Which microorganism is commonly used in the preparation of curd from milk?
(1) Rhizobium
(2) Lactobacillus
(3) Aspergillus
(4) Penicillium
Explanation: The correct answer is (2) Lactobacillus. It ferments lactose sugar in milk into lactic acid, leading to coagulation of milk proteins, forming curd. This process also enhances vitamin B content and improves digestibility of milk proteins in the diet.

2. Saccharomyces cerevisiae is commonly known as:
(1) Brewer’s yeast
(2) Cheese mold
(3) Wine fungus
(4) Bread bacterium
Explanation: The correct answer is (1) Brewer’s yeast. Saccharomyces cerevisiae ferments sugars to produce alcohol and carbon dioxide. It is widely used in brewing, winemaking, and baking industries for producing beer, wine, and bread through fermentation.

3. Which product is obtained from Propionibacterium sharmanii?
(1) Yogurt
(2) Swiss cheese
(3) Beer
(4) Wine
Explanation: The correct answer is (2) Swiss cheese. Propionibacterium sharmanii produces carbon dioxide gas during cheese ripening, forming characteristic holes in Swiss cheese while giving it a unique flavor and aroma profile.

4. What is the main use of Aspergillus niger in industries?
(1) Antibiotic production
(2) Citric acid production
(3) Alcohol fermentation
(4) Lactic acid production
Explanation: The correct answer is (2) Citric acid production. Aspergillus niger, a filamentous fungus, is cultured industrially for large-scale citric acid production used in beverages, pharmaceuticals, and as a preservative in the food industry.

5. Trichoderma polysporum is a source of:
(1) Cyclosporin A
(2) Streptomycin
(3) Penicillin
(4) Citric acid
Explanation: The correct answer is (1) Cyclosporin A. This immunosuppressive drug prevents organ transplant rejection by suppressing immune response and is produced by the fungus Trichoderma polysporum under controlled fermentation conditions.

6. Which organism is used for production of ethanol through fermentation?
(1) Clostridium acetobutylicum
(2) Saccharomyces cerevisiae
(3) Rhizopus stolonifer
(4) Penicillium chrysogenum
Explanation: The correct answer is (2) Saccharomyces cerevisiae. Also called brewer’s yeast, it converts sugars like glucose into ethanol and carbon dioxide under anaerobic conditions, forming the basis of alcohol production in beverages and biofuel industries.

7. Assertion–Reason Type:
Assertion (A): Lactobacillus plays a role in milk curdling.
Reason (R): It produces lactic acid that denatures milk protein casein.
(1) A and R are true, R correctly explains A
(2) A and R are true, but R does not explain A
(3) A is true, R is false
(4) A is false, R is true
Explanation: The correct answer is (1). Lactobacillus ferments lactose into lactic acid. The acid lowers pH, causing casein to coagulate, resulting in curd formation. Thus, lactic acid production directly explains the curdling process in milk fermentation.

8. Matching Type:
Match the microorganisms with their products:
A. Saccharomyces cerevisiae → i. Bread
B. Lactobacillus → ii. Curd
C. Aspergillus niger → iii. Citric acid
D. Trichoderma polysporum → iv. Cyclosporin A
(1) A-i, B-ii, C-iii, D-iv
(2) A-ii, B-i, C-iv, D-iii
(3) A-iii, B-iv, C-ii, D-i
(4) A-i, B-iii, C-ii, D-iv
Explanation: The correct answer is (1). Saccharomyces cerevisiae helps make bread; Lactobacillus forms curd; Aspergillus niger produces citric acid; Trichoderma polysporum yields cyclosporin A. Each organism is specialized for industrial or domestic bioprocess applications.

9. Fill in the Blanks:
The microorganism used in bread-making for CO2 production is ______.
(1) Penicillium
(2) Rhizopus
(3) Saccharomyces cerevisiae
(4) Clostridium
Explanation: The correct answer is (3) Saccharomyces cerevisiae. This yeast ferments glucose, producing carbon dioxide that makes bread dough rise, giving it soft texture and porous structure after baking.

10. Choose the Correct Statements:
Statement I: Propionibacterium sharmanii contributes to Swiss cheese flavor.
Statement II: Lactobacillus produces antibiotics used in cheese preservation.
(1) Both statements are true
(2) Both statements are false
(3) Statement I is true, II is false
(4) Statement I is false, II is true
Explanation: The correct answer is (3). Propionibacterium sharmanii produces CO2 and organic acids imparting Swiss cheese flavor. However, Lactobacillus does not produce antibiotics; it ferments milk sugar to lactic acid for curd formation.

Topic: Nitrogen Metabolism; Subtopic: Biological Nitrogen Fixation

Keyword Definitions:

• Nitrogen fixation: The process of converting atmospheric nitrogen (N₂) into ammonia (NH₃) by certain microorganisms.

• Azotobacter: A free-living aerobic bacterium capable of fixing atmospheric nitrogen in the soil.

• Anabaena: A filamentous cyanobacterium with specialized cells called heterocysts for nitrogen fixation.

• Nostoc: A cyanobacterium forming colonies in moist environments that fixes nitrogen through heterocysts.

• Oscillatoria: A filamentous cyanobacterium that lacks heterocysts and cannot fix nitrogen.

• Volvox: A colonial green alga without nitrogen-fixing ability.

Lead Question – 2025

Which of the following organisms cannot fix nitrogen?
A. Azotobacter
B. Oscillatoria
C. Anabaena
D. Volvox
E. Nostoc
Choose the correct answer from the options given below:
(1) A only
(2) D only
(3) B only
(4) E only

Explanation: Nitrogen fixation is carried out by certain prokaryotes like Azotobacter (bacteria) and cyanobacteria such as Anabaena and Nostoc. These organisms contain nitrogenase enzyme, which reduces N₂ to NH₃. Oscillatoria lacks heterocysts and hence cannot fix nitrogen. Volvox is an alga without nitrogenase. Therefore, the correct answer is (3) B only.

Guessed Questions:

1. Which enzyme is essential for nitrogen fixation?
(1) Nitrogenase
(2) Nitrate reductase
(3) Nitrite reductase
(4) Dehydrogenase

Explanation: Nitrogenase is a complex enzyme responsible for reducing atmospheric nitrogen (N₂) into ammonia (NH₃). It is highly oxygen-sensitive and functions under anaerobic or microaerophilic conditions, primarily in heterocysts or root nodules of nitrogen-fixing organisms.

2. The process of converting ammonia into nitrates is called:
(1) Nitrification
(2) Denitrification
(3) Ammonification
(4) Assimilation

Explanation: Nitrification is the two-step process in which ammonia is converted to nitrite by Nitrosomonas and then to nitrate by Nitrobacter. It is an essential part of the nitrogen cycle facilitating the availability of nitrogen to plants in absorbable forms.

3. Which of the following symbiotic associations is correctly matched?
(1) Rhizobium – Leguminous roots
(2) Nostoc – Rice root nodules
(3) Azospirillum – Lichen
(4) Frankia – Algae

Explanation: Rhizobium forms symbiotic nodules with leguminous roots where nitrogen fixation occurs. Nostoc and Frankia have associations with other hosts, but not rice roots or algae respectively. Azospirillum associates with cereal rhizospheres, not lichens.

4. Assertion (A): Nitrogen fixation requires high energy input.
Reason (R): Conversion of N₂ to NH₃ involves breaking a triple bond in N₂.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: Breaking the triple bond in molecular nitrogen (N≡N) requires a large amount of energy (about 16 ATP per N₂ molecule). Hence, nitrogen fixation is an energy-intensive process catalyzed by nitrogenase. Therefore, both statements are true, and R correctly explains A.

5. Match the following:
A. Rhizobium → I. Root nodules
B. Nostoc → II. Free-living cyanobacterium
C. Azotobacter → III. Free-living aerobic bacterium
D. Frankia → IV. Non-legume nodules
Choose the correct answer:
(1) A-I, B-II, C-III, D-IV
(2) A-II, B-I, C-IV, D-III
(3) A-III, B-IV, C-I, D-II
(4) A-IV, B-II, C-III, D-I

Explanation: Rhizobium forms root nodules with legumes, Nostoc is a free-living cyanobacterium, Azotobacter is a free-living aerobic bacterium, and Frankia forms nodules with non-leguminous plants like Alnus. Thus, option (1) is correct.

6. The energy required for nitrogen fixation is provided by:
(1) ATP
(2) ADP
(3) AMP
(4) GTP

Explanation: Nitrogenase enzyme requires a large amount of ATP to convert nitrogen (N₂) into ammonia (NH₃). The process typically consumes 16 molecules of ATP per molecule of N₂ reduced. The energy is generated through photosynthesis or respiration in the microorganism.

7. Fill in the Blanks:
The site of nitrogen fixation in cyanobacteria is ________.
(1) Vegetative cell
(2) Heterocyst
(3) Spore
(4) Thallus

Explanation: Heterocysts are specialized thick-walled cells in filamentous cyanobacteria such as Nostoc and Anabaena that provide an anaerobic environment necessary for nitrogenase activity, thus serving as the site of nitrogen fixation.

8. Statement I: Oscillatoria lacks heterocysts.
Statement II: It can fix atmospheric nitrogen.
(1) Both statements are true.
(2) Both statements are false.
(3) Statement I is true, Statement II is false.
(4) Statement I is false, Statement II is true.

Explanation: Oscillatoria lacks heterocysts and nitrogenase enzyme, hence cannot fix atmospheric nitrogen. It depends on combined nitrogen sources from the environment. Therefore, Statement I is true, and Statement II is false.

9. Which of the following processes converts nitrate to gaseous nitrogen?
(1) Denitrification
(2) Nitrification
(3) Assimilation
(4) Ammonification

Explanation: Denitrification is a microbial process carried out by bacteria like Pseudomonas and Bacillus under anaerobic conditions. It reduces nitrates (NO₃⁻) to nitrogen gas (N₂), returning nitrogen to the atmosphere and completing the nitrogen cycle.

10. Which of the following organisms is both photosynthetic and nitrogen-fixing?
(1) Azotobacter
(2) Rhizobium
(3) Nostoc
(4) Frankia

Explanation: Nostoc is a photosynthetic cyanobacterium that can fix atmospheric nitrogen through heterocysts. It performs photosynthesis in vegetative cells and nitrogen fixation in specialized cells, thus combining autotrophic and diazotrophic functions efficiently.

Topic: Microbes in Industrial Products; Subtopic: Medicinal Uses of Microbes

Keyword Definitions:

• Streptokinase: An enzyme produced by Streptococcus bacteria, used as a clot-dissolving agent in medical treatments.

• Thrombolytic agent: A compound that helps dissolve blood clots in blood vessels.

• Streptococcus: A genus of bacteria responsible for various infections and also used in biotechnology.

• Clot: A semi-solid mass formed from blood to stop bleeding, but harmful when formed in vessels.

• Microbial therapy: Use of microorganisms or their products for curing diseases.

Lead Question – (2025)

Streptokinase produced by bacterium Streptococcus is used for:

(1) Curd production

(2) Ethanol production

(3) Liver disease treatment

(4) Removing clots from blood vessels

Explanation:

Streptokinase, produced by Streptococcus bacteria, is a medically important enzyme used as a thrombolytic agent to remove clots from blood vessels of patients suffering from myocardial infarction. It converts plasminogen to plasmin, which dissolves fibrin clots and restores blood flow. It is not used for curd or ethanol production. Hence, the correct answer is (4) Removing clots from blood vessels.

1. Which of the following microbes is used in the production of streptokinase?

(1) Penicillium notatum

(2) Streptococcus

(3) Aspergillus niger

(4) Rhizopus stolonifer

Explanation:

Streptokinase is obtained from the bacterium Streptococcus. This enzyme helps in dissolving blood clots by converting plasminogen into plasmin. It is used as a therapeutic agent in heart attack patients. Streptococcus thus plays a major role in biotechnology for the manufacture of clot-dissolving drugs.

2. Streptokinase acts by converting:

(1) Fibrin into fibrinogen

(2) Plasminogen into plasmin

(3) Fibrinogen into thrombin

(4) Prothrombin into thrombin

Explanation:

Streptokinase works as a thrombolytic enzyme that converts plasminogen into plasmin. Plasmin is an active enzyme that digests fibrin, the main protein forming blood clots. This action helps dissolve clots in the arteries and restore normal blood circulation. Hence, the correct answer is (2) Plasminogen into plasmin.

3. Which disease condition is treated using Streptokinase?

(1) Tuberculosis

(2) Myocardial infarction

(3) Liver cirrhosis

(4) Asthma

Explanation:

Streptokinase is a life-saving enzyme used in the treatment of myocardial infarction (heart attack). It dissolves clots that block coronary arteries, helping restore blood flow to the heart. Early administration greatly reduces tissue damage and death. It is not used for liver or respiratory diseases. Thus, the answer is (2) Myocardial infarction.

4. Which of the following is an example of a microbial product used in medicine?

(1) Penicillin

(2) Streptokinase

(3) Cyclosporin-A

(4) All of these

Explanation:

Microbes contribute many medical products such as Penicillin (antibiotic from Penicillium), Streptokinase (clot-buster from Streptococcus), and Cyclosporin-A (immunosuppressive drug from Trichoderma). These have revolutionized healthcare and surgery. Hence, the correct answer is (4) All of these.

5. Which of the following enzymes is used to dissolve blood clots?

(1) Lipase

(2) Amylase

(3) Streptokinase

(4) Cellulase

Explanation:

Among the given enzymes, Streptokinase is specifically used as a clot-dissolving or thrombolytic enzyme. It helps convert plasminogen into plasmin, breaking down fibrin in the clot. This enzyme is widely used in hospitals to treat patients with heart attacks or blocked arteries.

6. Which microbial enzyme is used in removing fibrin clots from blood vessels?

(1) Pectinase

(2) Streptokinase

(3) Amylase

(4) Protease

Explanation:

Fibrin clots are dissolved using Streptokinase enzyme obtained from Streptococcus. This enzyme helps restore normal blood flow by breaking fibrin mesh in clots. Amylase and pectinase act on carbohydrates, not proteins like fibrin. Therefore, the correct answer is (2) Streptokinase.

7. Assertion–Reason Type Question

Assertion (A): Streptokinase is used as a thrombolytic agent.

Reason (R): It converts fibrinogen into thrombin to dissolve clots.

(1) Both A and R are true, and R correctly explains A

(2) Both A and R are true, but R does not explain A

(3) A is true but R is false

(4) A is false but R is true

Explanation:

Streptokinase is indeed a thrombolytic agent, but it converts plasminogen to plasmin, not fibrinogen to thrombin. Plasmin then breaks fibrin clots. Hence, Assertion is true but Reason is false. The correct answer is (3) A is true but R is false.

8. Matching Type Question

Match the following microbial products with their uses:

A. Streptokinase

B. Penicillin

C. Cyclosporin-A

D. Lactobacillus

1. Immunosuppressive agent

2. Antibiotic

3. Clot-buster

4. Curd production

Options:

(1) A-3, B-2, C-1, D-4

(2) A-2, B-3, C-1, D-4

(3) A-4, B-1, C-2, D-3

(4) A-3, B-1, C-4, D-2

Explanation:

Streptokinase – clot-buster, Penicillin – antibiotic, Cyclosporin-A – immunosuppressive drug, and Lactobacillus – curd production. These microbial products serve distinct medicinal and industrial roles. Hence, the correct match is (1) A-3, B-2, C-1, D-4.

9. Fill in the Blanks

Streptokinase is used as a ______ agent to remove clots from blood vessels.

(1) Antibiotic

(2) Thrombolytic

(3) Immunosuppressive

(4) Antiviral

Explanation:

Streptokinase is a thrombolytic agent that dissolves blood clots by converting plasminogen to plasmin. It is used clinically for treating blocked blood vessels in heart attack and stroke patients. It is not an antibiotic or antiviral. Hence, the correct answer is (2) Thrombolytic.

10. Choose the Correct Statements

Statement I: Streptokinase helps in dissolving fibrin clots.

Statement II: Streptokinase is produced by Penicillium notatum.

(1) Both statements are correct

(2) Both statements are incorrect

(3) Statement I is correct but Statement II is incorrect

(4) Statement I is incorrect but Statement II is correct

Explanation:

Streptokinase dissolves fibrin clots and is produced by Streptococcus, not by Penicillium. Hence, Statement I is correct but Statement II is incorrect. It is a vital enzyme used for treating blood clots and heart attacks. Therefore, the correct answer is (3).

Topic: Industrial Products from Microbes; Subtopic: Alcoholic Beverages

Keyword Definitions:

• Yeast: Unicellular fungi used in fermentation to produce alcohol.

• Fermentation: Conversion of sugars into alcohol and CO₂ by microbes under anaerobic conditions.

• Alcoholic Beverage: Drink containing ethanol formed by fermentation or distillation.

• Non-distilled Beverage: Alcoholic drink not distilled, containing low alcohol percentage.

Lead Question - 2025

Which of the following is an example of non-distilled alcoholic beverage produced by yeast?

(1) Whisky

(2) Brandy

(3) Beer

(4) Rum

Explanation: Non-distilled alcoholic beverages are produced by fermentation without distillation. Beer and wine are common examples. They are brewed using Saccharomyces cerevisiae, which ferments sugars into ethanol and CO₂. Distilled beverages like whisky, rum, and brandy are concentrated by distillation. Answer: Beer.

1. Which microorganism is used in the production of wine?

(1) Penicillium

(2) Rhizopus

(3) Saccharomyces cerevisiae

(4) Aspergillus niger

Explanation: Wine is made from fermentation of grape juice by Saccharomyces cerevisiae. Yeast converts sugars into ethanol and CO₂ under anaerobic conditions. Proper temperature and pH are important for aroma and flavor. The process produces varying alcohol content depending on yeast and duration. Answer: Saccharomyces cerevisiae.

2. Which of the following beverages is obtained by distillation?

(1) Wine

(2) Beer

(3) Brandy

(4) Toddy

Explanation: Distillation increases alcohol concentration by separating ethanol from fermented liquid. Brandy is distilled from fermented grape juice, whereas wine and beer are non-distilled. Distillation removes impurities and raises ethanol levels. Answer: Brandy.

3. The main product of yeast fermentation of glucose is —

(1) Lactic acid

(2) Ethanol and CO₂

(3) Acetic acid

(4) Propionic acid

Explanation: Yeast converts glucose to ethanol and CO₂ under anaerobic conditions using zymase enzymes. Ethanol forms the alcoholic content while CO₂ is released as gas. This process forms the basis for brewing and baking industries. Answer: Ethanol and CO₂.

4. Which of the following is a distilled beverage derived from sugarcane molasses?

(1) Beer

(2) Wine

(3) Rum

(4) Toddy

Explanation: Rum is made by fermenting and distilling sugarcane molasses. Yeast ferments the sugar into alcohol, followed by distillation to concentrate ethanol. The liquid is aged in barrels for flavor and aroma. Answer: Rum.

5. The yeast used in bread making produces —

(1) Ethanol and carbon dioxide

(2) Lactic acid

(3) Butyric acid

(4) Acetic acid

Explanation: In bread making, yeast fermentation releases CO₂ which causes dough to rise. Ethanol evaporates during baking. The CO₂ makes bread soft and porous. Saccharomyces cerevisiae is the common yeast used. Answer: Ethanol and carbon dioxide.

6. Which of the following beverages is produced by the fermentation of barley malt?

(1) Whisky

(2) Beer

(3) Rum

(4) Brandy

Explanation: Beer is made by fermenting malted barley using brewer’s yeast. The malt provides fermentable sugars, and hops add bitterness and aroma. Alcohol content ranges between 3–6%. Answer: Beer.

7. Assertion–Reason Question:

Assertion (A): Ethanol is produced during anaerobic fermentation.

Reason (R): Oxygen helps in oxidation of glucose to lactic acid in yeast.

(1) Both A and R are true and R is correct explanation

(2) Both A and R are true but R is not the correct explanation

(3) A is true but R is false

(4) A is false but R is true

Explanation: Yeast produces ethanol under anaerobic conditions, not lactic acid. Oxygen presence halts fermentation and causes aerobic respiration. Therefore, A is true and R is false. Answer: A is true but R is false.

8. Matching Type Question:

A. Beer – I. Distilled beverage

B. Rum – II. From sugarcane molasses

C. Wine – III. Fermented grape juice

D. Whisky – IV. From malted barley

(1) A-III, B-II, C-IV, D-I

(2) A-IV, B-II, C-III, D-I

(3) A-II, B-I, C-III, D-IV

(4) A-III, B-IV, C-II, D-I

Explanation: Beer is from malted barley, rum from sugarcane molasses, wine from grapes, whisky is distilled from malted cereals. Each involves unique fermentation and aging methods. Answer: A-IV, B-II, C-III, D-I.

9. Fill in the Blank Question:

_____ is the process by which sugar is converted into alcohol by microorganisms.

(1) Distillation

(2) Fermentation

(3) Pasteurization

(4) Sterilization

Explanation: Fermentation is the biological process where yeast converts sugar into ethanol and CO₂. It forms the basis of brewing, wine-making, and bioethanol production. Louis Pasteur discovered its microbial nature. Answer: Fermentation.

10. Choose the Correct Statements (Statement I & II):

Statement I: Wine is a distilled beverage.

Statement II: Beer is a fermented but non-distilled beverage.

(1) Both statements are true

(2) Both statements are false

(3) Statement I is false but Statement II is true

(4) Statement I is true but Statement II is false

Explanation: Wine is not distilled; it’s obtained by fermentation of grapes. Beer is also fermented but not distilled. Distilled beverages include whisky and rum. Therefore, only Statement II is correct. Answer: Statement I is false but Statement II is true.

Topic: Industrial Products of Microorganisms; Subtopic: Industrial Applications of Fungi and Bacteria

Keyword Definitions:

• Microbes: Microscopic living organisms including bacteria, fungi, protozoa, and viruses used in industrial, medical, and environmental processes.

• Fermentation: An anaerobic process by which microorganisms convert sugars into alcohol, acids, or gases.

• Citric acid: An organic acid produced industrially by Aspergillus niger used in food, pharmaceuticals, and cleaning agents.

• Cyclosporin-A: An immunosuppressive drug produced by Trichoderma polysporum, used to prevent organ transplant rejection.

• Ethanol: An alcohol produced by Saccharomyces cerevisiae during fermentation of sugars, used as a biofuel and in beverages.

Lead Question - 2024 (Jhajjhar)

Match List-I with List-II:
List-I
A. Saccharomyces cerevisiae
B. Aspergillus niger
C. Trichoderma polysporum
D. Clostridium butylicum

List-II
I. Citric acid
II. Butyric acid
III. Ethanol
IV. Cyclosporin-A

Choose the correct answer from the options given below:
1. A-III, B-I, C-IV, D-II
2. A-IV, B-II, C-III, D-I
3. A-III, B-IV, C-I, D-II
4. A-I, B-III, C-II, D-IV

Explanation: The correct answer is option 1 (A-III, B-I, C-IV, D-II). Saccharomyces cerevisiae produces ethanol through fermentation. Aspergillus niger synthesizes citric acid industrially. Trichoderma polysporum forms cyclosporin-A, an immunosuppressive drug, while Clostridium butylicum produces butyric acid. These microbes have immense industrial applications in medicine, food processing, and biofuel production.

Guessed Questions:

1. Which microorganism is commonly used for ethanol production in industries?
1. Aspergillus niger
2. Saccharomyces cerevisiae
3. Lactobacillus acidophilus
4. Rhizobium leguminosarum
Explanation: The correct answer is 2. Saccharomyces cerevisiae, known as baker’s yeast, ferments sugars into ethanol and carbon dioxide. This process is utilized in alcoholic beverages and biofuel industries. It represents one of the earliest examples of human use of microbes for beneficial purposes.

2. Citric acid is produced commercially using which of the following fungi?
1. Penicillium chrysogenum
2. Aspergillus niger
3. Trichoderma polysporum
4. Candida albicans
Explanation: The correct answer is 2. Aspergillus niger is used to produce citric acid at large scale through fermentation. This acid is an important additive in food and beverages, pharmaceuticals, and cleaning products, showing the significance of industrial microbiology in daily life.

3. Which antibiotic-like compound is obtained from Trichoderma polysporum?
1. Streptomycin
2. Penicillin
3. Cyclosporin-A
4. Tetracycline
Explanation: The correct answer is 3. Trichoderma polysporum produces Cyclosporin-A, a cyclic peptide that suppresses immune response, preventing organ transplant rejection. Its discovery revolutionized transplant medicine, highlighting the pharmaceutical value of fungal metabolites.

4. Which bacterium is responsible for the production of butyric acid?
1. Clostridium butylicum
2. Rhizobium meliloti
3. Lactobacillus bulgaricus
4. Streptococcus thermophilus
Explanation: The correct answer is 1. Clostridium butylicum is an anaerobic bacterium that ferments carbohydrates into butyric acid. This compound is used in pharmaceuticals, perfumes, and as a precursor in chemical industries, demonstrating the economic role of microbial fermentation.

5. Which of the following is a microbial product used as an immunosuppressive agent?
1. Erythromycin
2. Cyclosporin-A
3. Penicillin
4. Streptokinase
Explanation: The correct answer is 2. Cyclosporin-A, produced by Trichoderma polysporum, suppresses immune activity in organ transplant patients, preventing rejection. It selectively inhibits T-cell activation and has become a vital drug in modern immunology and clinical medicine.

6. Which of the following microbial products is used in the food and beverage industry as a flavor enhancer and preservative?
1. Citric acid
2. Cyclosporin-A
3. Butyric acid
4. Ethanol
Explanation: The correct answer is 1. Citric acid, produced by Aspergillus niger, acts as a natural preservative and flavoring agent in soft drinks, jams, and confectionery. It also stabilizes food pH and prevents microbial spoilage, ensuring product safety and extended shelf life.

7. Assertion-Reason Type:
Assertion (A): Ethanol fermentation by yeast is an aerobic process.
Reason (R): Oxygen is required for ethanol formation.
1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation.
3. A is true, but R is false.
4. A is false, but R is true.
Explanation: The correct answer is 4. Ethanol fermentation by yeast is an anaerobic process that occurs without oxygen. Under anaerobic conditions, Saccharomyces cerevisiae converts glucose into ethanol and carbon dioxide, releasing energy. Presence of oxygen diverts metabolism towards biomass formation.

8. Matching Type:
Match the following industrial products with their producing microorganisms:
A. Penicillin    I. Aspergillus niger
B. Citric acid    II. Penicillium chrysogenum
C. Lactic acid    III. Lactobacillus sp.
D. Butyric acid    IV. Clostridium butylicum

1. A-II, B-I, C-III, D-IV
2. A-I, B-II, C-IV, D-III
3. A-III, B-IV, C-II, D-I
4. A-II, B-IV, C-I, D-III
Explanation: The correct answer is 1. Penicillin is produced by Penicillium chrysogenum, citric acid by Aspergillus niger, lactic acid by Lactobacillus, and butyric acid by Clostridium butylicum. These microbes are utilized worldwide in industrial bioprocesses to synthesize valuable products.

9. Fill in the Blanks:
Cyclosporin-A produced by __________ is used to prevent organ transplant rejection.
1. Aspergillus niger
2. Trichoderma polysporum
3. Saccharomyces cerevisiae
4. Clostridium butylicum
Explanation: The correct answer is 2. Cyclosporin-A, produced by Trichoderma polysporum, suppresses immune response, making it essential in transplant surgeries. It selectively targets T-lymphocytes, preventing rejection and ensuring graft survival. Its discovery marked a breakthrough in immunosuppressive therapy.

10. Choose the Correct Statements (Statement I & Statement II):
Statement I: Aspergillus niger is used in citric acid production.
Statement II: Saccharomyces cerevisiae produces lactic acid during fermentation.
1. Both statements are correct.
2. Both statements are incorrect.
3. Statement I is correct but Statement II is incorrect.
4. Statement I is incorrect but Statement II is correct.
Explanation: The correct answer is 3. Aspergillus niger synthesizes citric acid, a valuable organic acid. Saccharomyces cerevisiae produces ethanol, not lactic acid. Lactic acid is produced by Lactobacillus species. Thus, only Statement I correctly describes industrial microbial product formation.

Topic: Industrial Microbiology; Subtopic: Microbial Products

Keyword Definitions:

• Clostridium butylicum: Anaerobic bacterium used in butyric acid production.

• Saccharomyces cerevisiae: Yeast used in ethanol fermentation.

• Trichoderma polysporum: Fungus producing antibiotics like cyclosporin-A.

• Streptococcus sp.: Bacteria producing enzymes like streptokinase.

• Ethanol: Alcohol produced by yeast fermentation.

• Butyric acid: Short-chain fatty acid produced by Clostridium species.

• Cyclosporin-A: Immunosuppressant produced by fungi.

• Streptokinase: Enzyme used in thrombolytic therapy.

Lead Question – 2024

Match List I with List II:

List I  List II
A. Clostridium butylicum I. Ethanol
B. Saccharomyces cerevisiae II. Streptokinase
C. Trichoderma polysporum III. Butyric Acid
D. Streptococcus sp. IV. Cyclosporin–A

Choose the correct answer from the options below:
(1) A–II, B–IV, C–III, D–I
(2) A–III, B–I, C–IV, D–II
(3) A–IV, B–I, C–III, D–II
(4) A–III, B–I, C–II, D–IV

Explanation: Clostridium butylicum produces butyric acid through anaerobic fermentation. Saccharomyces cerevisiae ferments sugars to produce ethanol. Trichoderma polysporum synthesizes cyclosporin-A, an immunosuppressive drug. Streptococcus species produce streptokinase, a fibrinolytic enzyme used medically. Matching these microorganisms with their respective products illustrates industrial applications of microbes in pharmaceuticals, biofuels, and chemicals. This understanding is crucial in microbial biotechnology, showing the specificity of products associated with different microbial species. The correct pairing is A–III, B–I, C–IV, D–II. (Answer: 2)

1. Single Correct Answer:
Which microorganism is primarily used for industrial ethanol production?
(1) Clostridium butylicum
(2) Saccharomyces cerevisiae
(3) Trichoderma polysporum
(4) Streptococcus sp.

Explanation: Saccharomyces cerevisiae, a yeast, is the key microorganism used in industrial ethanol production via fermentation of sugars. It converts glucose and other fermentable sugars to ethanol and carbon dioxide under anaerobic conditions. Other organisms like Clostridium produce acids, Trichoderma produce antibiotics, and Streptococcus produces enzymes, not ethanol. (Answer: 2)

2. Single Correct Answer:
Which product is obtained from Clostridium butylicum fermentation?
(1) Ethanol
(2) Streptokinase
(3) Butyric acid
(4) Cyclosporin-A

Explanation: Clostridium butylicum produces butyric acid as a primary metabolite during anaerobic fermentation. This short-chain fatty acid is utilized in chemical industries. It does not produce ethanol (yeast), streptokinase (Streptococcus), or cyclosporin-A (Trichoderma). The correct identification of microbial product is important for industrial microbiology applications. (Answer: 3)

3. Single Correct Answer:
Trichoderma polysporum is industrially significant for production of:
(1) Butyric acid
(2) Streptokinase
(3) Cyclosporin-A
(4) Ethanol

Explanation: Trichoderma polysporum produces cyclosporin-A, an immunosuppressant drug used in organ transplantation to prevent rejection. It does not produce butyric acid (Clostridium), streptokinase (Streptococcus), or ethanol (Saccharomyces). Understanding microbial secondary metabolites is crucial in pharmaceutical biotechnology. (Answer: 3)

4. Single Correct Answer:
Which microorganism is used in thrombolytic therapy?
(1) Clostridium butylicum
(2) Saccharomyces cerevisiae
(3) Streptococcus sp.
(4) Trichoderma polysporum

Explanation: Streptococcus species produce streptokinase, an enzyme that dissolves blood clots and is used in thrombolytic therapy. Other microbes like Clostridium, Saccharomyces, and Trichoderma do not produce this enzyme, and are used in other industrial applications such as acids, ethanol, or immunosuppressants. (Answer: 3)

5. Single Correct Answer:
Which of the following is a fungal secondary metabolite?
(1) Butyric acid
(2) Ethanol
(3) Cyclosporin-A
(4) Streptokinase

Explanation: Cyclosporin-A is a secondary metabolite produced by Trichoderma polysporum fungus. Secondary metabolites are non-essential but medically significant products like antibiotics and immunosuppressants. Butyric acid is bacterial, ethanol is microbial primary metabolite from yeast, and streptokinase is bacterial enzyme. (Answer: 3)

6. Single Correct Answer:
Which product results from anaerobic fermentation?
(1) Cyclosporin-A
(2) Streptokinase
(3) Ethanol
(4) Butyric acid

Explanation: Anaerobic fermentation by microbes like Clostridium butylicum produces butyric acid. Saccharomyces cerevisiae also produces ethanol anaerobically. Cyclosporin-A and streptokinase are not fermentation products. Both ethanol and butyric acid are classical anaerobic metabolites. (Answer: 4)

7. Assertion-Reason:
Assertion (A): Saccharomyces cerevisiae is used for ethanol production.
Reason (R): It performs anaerobic fermentation converting sugars to ethanol.
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A true, R false
(4) A false, R true

Explanation: Saccharomyces cerevisiae produces ethanol by anaerobic fermentation of sugars, converting glucose to ethanol and carbon dioxide. Both the assertion and reason are true, and the reason correctly explains why S. cerevisiae is industrially used for ethanol production. (Answer: 1)

8. Matching Type:
Match Microbe with Product:
A. Clostridium butylicum – (i) Butyric acid
B. Saccharomyces cerevisiae – (ii) Ethanol
C. Trichoderma polysporum – (iii) Cyclosporin-A
D. Streptococcus sp. – (iv) Streptokinase
Options:
(1) A-i, B-ii, C-iii, D-iv
(2) A-ii, B-i, C-iv, D-iii
(3) A-iv, B-iii, C-ii, D-i
(4) A-iii, B-iv, C-i, D-ii

Explanation: Correct microbial-product pairing is: Clostridium butylicum produces butyric acid, Saccharomyces cerevisiae produces ethanol, Trichoderma polysporum produces cyclosporin-A, and Streptococcus sp. produces streptokinase. This illustrates industrial applications of microbes in producing acids, alcohol, immunosuppressants, and enzymes. (Answer: 1)

9. Fill in the Blanks:
___ is used to produce ethanol industrially, while ___ produces streptokinase.
(1) Saccharomyces cerevisiae, Streptococcus sp.
(2) Clostridium butylicum, Trichoderma polysporum
(3) Trichoderma polysporum, Clostridium butylicum
(4) Streptococcus sp., Saccharomyces cerevisiae

Explanation: Saccharomyces cerevisiae ferments sugars to ethanol, while Streptococcus species produce streptokinase. Clostridium produces acids, Trichoderma produces cyclosporin-A. Correct identification of microbial products is important for industrial and pharmaceutical applications. (Answer: 1)

10. Choose Correct Statements:
Statement I: Clostridium butylicum produces butyric acid.
Statement II: Trichoderma polysporum produces cyclosporin-A.
Options:
(1) Both statements are true
(2) Statement I true, Statement II false
(3) Statement I false, Statement II true
(4) Both statements are false

Explanation: Clostridium butylicum produces butyric acid via anaerobic fermentation, and Trichoderma polysporum synthesizes cyclosporin-A, an immunosuppressant. Both statements accurately reflect microbial products and their industrial significance. (Answer: 1)

Chapter: Microbes in Human Welfare: Topic: Microbes in Industrial Products; Subtopic: Spirulina and Its Applications

Keyword Definitions:

• Spirulina: A photosynthetic cyanobacterium used as a protein-rich food supplement.

• Microbe: A microscopic organism like bacteria, fungi, or algae with various ecological and industrial roles.

• Environmental pollution: The contamination of air, water, or soil due to harmful substances.

• Protein source: A biological or synthetic material rich in amino acids necessary for body growth and repair.

• Biofertilizer: A natural substance containing living microorganisms that promote plant growth by increasing soil fertility.

Lead Question - 2022 (Ganganagar)
ASSERTION-REASON TYPE QUESTION

Assertion (A): Spirulina is a microbe that can be used for reducing environmental pollution.
Reason (R): Spirulina is a rich source of protein, carbohydrates, fats, minerals and vitamins.

1. Both (A) and (R) are correct and (R) is the correct explanation of (A)
2. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
3. (A) is correct but (R) is not correct
4. (A) is not correct but (R) is correct

Explanation: Spirulina, a photosynthetic cyanobacterium, helps reduce environmental pollution by absorbing carbon dioxide and nitrogen compounds from wastewaters. It also serves as a protein-rich supplement containing essential nutrients. Hence, both statements are correct but (R) is not the correct explanation of (A). The correct answer is option 2.

Guessed Question 1: Spirulina is commonly used as a ___________.
1. Vitamin D supplement
2. Protein-rich food source
3. Antibiotic agent
4. Mineral supplement

Explanation: Spirulina is a cyanobacterium widely used as a dietary supplement due to its high protein content (up to 70%). It contains essential amino acids, vitamins, minerals, and antioxidants. It is cultivated in alkaline water bodies and used to combat malnutrition. Thus, the correct answer is protein-rich food source (Option 2).

Guessed Question 2: Spirulina belongs to which group of organisms?
1. Bacteria
2. Cyanobacteria
3. Green algae
4. Protozoa

Explanation: Spirulina is a filamentous cyanobacterium capable of photosynthesis. It is often grouped with microalgae due to its chlorophyll pigments. It can grow in brackish or alkaline water and is cultivated industrially as a nutritional supplement. Hence, Spirulina belongs to cyanobacteria (Option 2).

Guessed Question 3: Which pigment is responsible for photosynthesis in Spirulina?
1. Chlorophyll-a
2. Phycocyanin
3. Both 1 and 2
4. None of these

Explanation: Spirulina contains both chlorophyll-a and phycocyanin pigments that enable photosynthesis. Chlorophyll-a captures light energy, while phycocyanin gives Spirulina its characteristic blue-green color. These pigments make it a sustainable source of oxygen and biomass. Hence, both 1 and 2 are correct (Option 3).

Guessed Question 4: Spirulina can fix which of the following gases from the atmosphere?
1. CO2 only
2. N2 only
3. Both CO2 and N2
4. O2 only

Explanation: Spirulina can fix atmospheric CO2 through photosynthesis and some species can fix nitrogen (N2) due to the presence of specialized cells called heterocysts. These abilities make it useful for reducing carbon and nitrogen pollution. Thus, the correct answer is both CO2 and N2 (Option 3).

Guessed Question 5: Which one of the following is not a product derived from Spirulina?
1. Biofuel
2. Antibiotic
3. Nutrient supplement
4. Animal feed

Explanation: Spirulina is primarily cultivated for human and animal nutrition and for biofuel production. However, it does not produce antibiotics naturally. Instead, its extracts show mild antimicrobial activity due to its pigments. Hence, the correct answer is antibiotic (Option 2).

Guessed Question 6: Which of the following nutrients is most abundant in Spirulina?
1. Carbohydrates
2. Proteins
3. Fats
4. Vitamins

Explanation: Spirulina is rich in proteins, constituting nearly 60–70% of its dry weight. It contains all essential amino acids, making it a complete plant-based protein source. Carbohydrates and fats are present in smaller quantities, making it ideal for human consumption. Therefore, the correct answer is proteins (Option 2).

Guessed Question 7 (Matching Type): Match the following properties of Spirulina:
List I (Property) — List II (Description)
(a) Color pigment — (i) Phycocyanin
(b) Protein content — (ii) About 60–70% dry weight
(c) Oxygen evolution — (iii) Photosynthesis
(d) Nitrogen fixation — (iv) Atmospheric N2

1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
3. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
4. (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)

Explanation: Spirulina’s blue-green color is due to phycocyanin pigment. It contains 60–70% protein in dry weight, evolves oxygen via photosynthesis, and can fix atmospheric nitrogen. Hence, the correct match is (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv) (Option 1).

Guessed Question 8 (Fill in the Blank): Spirulina is often called a ___________ food because of its rich nutrient content.
1. Miracle
2. Poor man’s
3. Junk
4. Empty calorie

Explanation: Spirulina is often termed a “miracle food” because it contains nearly all essential nutrients required by humans — including proteins, vitamins, and minerals — in a highly digestible form. It is used to combat malnutrition globally. Hence, the correct answer is miracle (Option 1).

Guessed Question 9: Which of the following is an advantage of cultivating Spirulina?
1. It requires fertile soil
2. It can grow in waste and alkaline water
3. It depends on pesticides
4. It grows only under low light

Explanation: Spirulina cultivation requires minimal resources. It grows efficiently in alkaline, brackish, or even wastewater environments using sunlight and basic nutrients. It does not need pesticides or fertile soil, making it a sustainable option for protein production. Thus, option 2 is correct.

Guessed Question 10 (Choose the Correct Statements):
Statement I: Spirulina can reduce environmental pollution by utilizing waste carbon and nitrogen compounds.
Statement II: Spirulina cannot be used for human consumption.
1. Both statements are correct
2. Both statements are incorrect
3. Statement I is correct, Statement II is incorrect
4. Statement I is incorrect, Statement II is correct

Explanation: Spirulina is an eco-friendly organism that removes pollutants like CO2 and nitrogen from the environment while producing nutritious biomass. It is widely used as a food source for humans and animals. Hence, Statement I is correct, and Statement II is incorrect (Option 3).

Topic: Nitrogen Fixation; Subtopic: Free-living Nitrogen-Fixing Bacteria

Keyword Definitions:

• Free-living nitrogen-fixing bacteria: Bacteria capable of fixing atmospheric nitrogen independently in soil without symbiotic association.

• Rhizobium: Symbiotic nitrogen-fixing bacteria associated with legume root nodules.

• Frankia: Nitrogen-fixing actinomycetes forming symbiotic relationships with certain plants.

• Azotobacter: Aerobic, free-living nitrogen-fixing bacteria in soil.

• Beijerinckia: Free-living aerobic nitrogen-fixing soil bacteria.

• Anabaena: Nitrogen-fixing cyanobacteria, can be free-living or symbiotic.

• Rhodospirillum: Photosynthetic, nitrogen-fixing bacteria.

• Pseudomonas: Heterotrophic bacteria, generally not nitrogen-fixing.

• Thiobacillus: Chemolithotrophic bacteria oxidizing sulfur, not fixing nitrogen.

• Nitrogen fixation: Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) by bacteria.

• Aerobic bacteria: Bacteria requiring oxygen for growth and metabolism.

Lead Question - 2022 (Ganganagar)

Which of the following pair represents free living nitrogen fixing aerobic bacteria?

1. Rhizobium and Frankia

2. Azotobacter and Beijernickia

3. Anabaena and Rhodospirillum

4. Pseudomonas and Thiobacillus

Explanation: Free-living nitrogen-fixing bacteria are aerobic and function independently of plant hosts. Azotobacter and Beijerinckia are soil-dwelling, aerobic bacteria that fix nitrogen without symbiosis. Rhizobium and Frankia are symbiotic, requiring host plants. Anabaena and Rhodospirillum may fix nitrogen but are either photosynthetic or facultative anaerobes. Pseudomonas and Thiobacillus do not fix nitrogen. Thus, the correct answer is 2. Azotobacter and Beijerinckia. These bacteria enrich soil nitrogen content, enhancing fertility and supporting plant growth by converting atmospheric N₂ into biologically usable ammonia under aerobic conditions.

1. Single Correct Answer MCQ:

Which bacterium forms symbiotic nitrogen-fixing nodules in legumes?

a) Azotobacter

b) Rhizobium

c) Beijerinckia

d) Pseudomonas

Explanation: Rhizobium forms symbiotic associations with legumes, fixing nitrogen in root nodules. Azotobacter and Beijerinckia are free-living, and Pseudomonas is not nitrogen-fixing. Correct answer is b) Rhizobium.

2. Single Correct Answer MCQ:

Which of the following is a cyanobacterium capable of nitrogen fixation?

a) Anabaena

b) Azotobacter

c) Beijerinckia

d) Rhodospirillum

Explanation: Anabaena is a nitrogen-fixing cyanobacterium, sometimes symbiotic, sometimes free-living. Azotobacter and Beijerinckia are free-living soil bacteria, Rhodospirillum is photosynthetic. Correct answer is a) Anabaena.

3. Single Correct Answer MCQ:

Which nitrogen-fixing bacteria are aerobic and free-living?

a) Rhizobium and Frankia

b) Azotobacter and Beijerinckia

c) Anabaena and Rhodospirillum

d) Thiobacillus and Pseudomonas

Explanation: Azotobacter and Beijerinckia are free-living, aerobic bacteria fixing nitrogen independently of plants. Correct answer is b) Azotobacter and Beijerinckia.

4. Single Correct Answer MCQ:

Which bacteria are chemolithotrophic and not nitrogen-fixing?

a) Pseudomonas and Thiobacillus

b) Azotobacter and Beijerinckia

c) Rhizobium and Frankia

d) Anabaena and Rhodospirillum

Explanation: Pseudomonas and Thiobacillus do not fix nitrogen; Thiobacillus oxidizes sulfur. Azotobacter, Beijerinckia, Rhizobium, Frankia, Anabaena, and Rhodospirillum have nitrogen-fixing capabilities. Correct answer is a) Pseudomonas and Thiobacillus.

5. Single Correct Answer MCQ:

Nitrogen fixation by Azotobacter occurs under:

a) Anaerobic conditions

b) Aerobic conditions

c) Symbiotic association

d) Photosynthetic conditions

Explanation: Azotobacter is an aerobic, free-living bacterium that fixes nitrogen under oxygen-rich conditions. Correct answer is b) Aerobic conditions.

6. Single Correct Answer MCQ:

Beijerinckia is commonly found in:

a) Aquatic habitats

b) Soil

c) Animal gut

d) Leaf surfaces

Explanation: Beijerinckia is a free-living, aerobic nitrogen-fixing bacterium inhabiting soil. Correct answer is b) Soil.

7. Assertion-Reason MCQ:

Assertion (A): Rhizobium cannot fix nitrogen independently.

Reason (R): It requires a symbiotic relationship with legume roots.

a) Both A and R are true, R explains A

b) Both A and R are true, R does not explain A

c) A is true, R is false

d) A is false, R is true

Explanation: Rhizobium is symbiotic; it needs legume roots to fix nitrogen effectively. Both assertion and reason are true, and the reason explains the assertion. Correct answer is a) Both A and R are true, R explains A.

8. Matching Type MCQ:

Match bacteria with their characteristic:

Column I

A) Azotobacter

B) Rhizobium

C) Beijerinckia

D) Thiobacillus

Column II

1) Symbiotic nitrogen fixer

2) Aerobic, free-living nitrogen fixer

3) Sulfur oxidizer, non-fixer

4) Aerobic, free-living nitrogen fixer

Choices:

A-__ B-__ C-__ D-__

Explanation: Correct matches are: Azotobacter (A-2), Rhizobium (B-1), Beijerinckia (C-4), Thiobacillus (D-3). Azotobacter and Beijerinckia are aerobic free-living fixers, Rhizobium is symbiotic, Thiobacillus oxidizes sulfur.

9. Fill in the Blanks / Completion MCQ:

__________ is an aerobic, free-living nitrogen-fixing bacterium found in soil.

a) Rhizobium

b) Azotobacter

c) Frankia

d) Pseudomonas

Explanation: Azotobacter is an aerobic, free-living bacterium that fixes nitrogen independently in soil. Correct answer is b) Azotobacter.

10. Choose the correct statements MCQ (Statement I & II):

Statement I: Rhizobium fixes nitrogen only in symbiotic association.

Statement II: Azotobacter can fix nitrogen independently under aerobic conditions.

a) Both I and II are correct

b) Only I is correct

c) Only II is correct

d) Both are incorrect

Explanation: Rhizobium is symbiotic, requiring legumes, whereas Azotobacter is free-living and fixes nitrogen independently under aerobic conditions. Both statements are correct. Correct answer is a) Both I and II are correct. 

Topic: Nitrogen Metabolism; Subtopic: Nitrogen Fixation in Legumes

Keyword Definitions:

• Nitrogenase: Enzyme complex in root nodules that reduces atmospheric nitrogen to ammonia.

• Leguminous plants: Plants capable of symbiotic nitrogen fixation, forming root nodules.

• Root nodule: Specialized structure in legumes housing nitrogen-fixing bacteria.

• Leg haemoglobin: Oxygen-binding protein in nodules that protects nitrogenase from oxygen damage.

• Catalase: Enzyme that decomposes hydrogen peroxide into water and oxygen.

• Transaminase: Enzyme catalyzing amino group transfer between amino acids and keto acids.

• Glutamate dehydrogenase: Enzyme involved in ammonia assimilation.

• Ammonia: Product of nitrogen fixation used for amino acid synthesis.

• Oxygen sensitivity: Nitrogenase is highly sensitive to oxygen, requiring protection.

• Symbiosis: Mutualistic relationship between legumes and Rhizobium bacteria.

• Enzyme protection: Mechanism to prevent nitrogenase inactivation by oxygen.

Lead Question - 2022 (Ganganagar)

Which of the following protects nitrogenase inside the root nodule of a leguminous plant?

1. Catalase

2. Leg haemoglobin

3. Transaminase

4. Glutamate dehydrogenase

Explanation: Nitrogenase, the enzyme responsible for atmospheric nitrogen fixation, is highly sensitive to oxygen. In leguminous root nodules, leg haemoglobin binds oxygen, maintaining a low free oxygen concentration to protect nitrogenase while allowing respiration. Catalase decomposes hydrogen peroxide, transaminase transfers amino groups, and glutamate dehydrogenase assimilates ammonia; none protect nitrogenase from oxygen. Thus, leg haemoglobin ensures an oxygen-regulated environment, facilitating effective nitrogen fixation. The correct answer is 2. Leg haemoglobin. This mechanism is critical for symbiotic nitrogen fixation, providing ammonia to the plant while preserving nitrogenase activity in oxygen-exposed root nodules.

1. Single Correct Answer MCQ:

The enzyme responsible for nitrogen fixation in root nodules is:

a) Nitrogenase

b) Catalase

c) Glutamate dehydrogenase

d) Transaminase

Explanation: Nitrogenase catalyzes conversion of atmospheric N₂ to NH₃ in root nodules. Catalase, glutamate dehydrogenase, and transaminase have other metabolic roles and do not fix nitrogen. Correct answer is a) Nitrogenase.

2. Single Correct Answer MCQ:

Which protein maintains low free oxygen in nodules?

a) Leg haemoglobin

b) Rubisco

c) Phytochrome

d) Myoglobin

Explanation: Leg haemoglobin binds oxygen in nodules, preventing nitrogenase inactivation. Rubisco fixes carbon, phytochrome senses light, myoglobin is in animals. Correct answer is a) Leg haemoglobin.

3. Single Correct Answer MCQ:

Ammonia produced in nodules is assimilated by:

a) Catalase

b) Glutamate dehydrogenase

c) Leg haemoglobin

d) Nitrogenase

Explanation: Glutamate dehydrogenase incorporates NH₃ into amino acids. Nitrogenase produces ammonia, leg haemoglobin protects enzyme, catalase decomposes H₂O₂. Correct answer is b) Glutamate dehydrogenase.

4. Single Correct Answer MCQ:

Root nodules are found in:

a) Grasses

b) Legumes

c) Mosses

d) Ferns

Explanation: Leguminous plants develop symbiotic root nodules with Rhizobium bacteria for nitrogen fixation. Grasses, mosses, and ferns do not form such nodules. Correct answer is b) Legumes.

5. Single Correct Answer MCQ:

The main function of leg haemoglobin is:

a) Fix nitrogen

b) Transport amino acids

c) Protect nitrogenase from oxygen

d) Convert ammonia to nitrate

Explanation: Leg haemoglobin binds free oxygen in nodules, preventing nitrogenase inactivation. It does not fix nitrogen, transport amino acids, or convert ammonia to nitrate. Correct answer is c) Protect nitrogenase from oxygen.

6. Single Correct Answer MCQ:

Catalase in root nodules functions to:

a) Protect nitrogenase

b) Decompose H₂O₂

c) Fix nitrogen

d) Bind oxygen

Explanation: Catalase breaks down hydrogen peroxide into water and oxygen, protecting cellular components from oxidative damage. It does not directly protect nitrogenase from oxygen. Correct answer is b) Decompose H₂O₂.

7. Assertion-Reason MCQ:

Assertion (A): Nitrogenase is sensitive to oxygen.

Reason (R): Leg haemoglobin maintains low free oxygen in nodules.

a) Both A and R are true, R explains A

b) Both A and R are true, R does not explain A

c) A is true, R is false

d) A is false, R is true

Explanation: Nitrogenase is inactivated by oxygen. Leg haemoglobin binds free oxygen, keeping concentration low and protecting nitrogenase. Both A and R are true, and R explains A. Correct answer is a) Both A and R are true, R explains A.

8. Matching Type MCQ:

Match enzyme/protein with its function in root nodules:

Column I

A) Nitrogenase

B) Leg haemoglobin

C) Catalase

D) Glutamate dehydrogenase

Column II

1) Ammonia assimilation

2) Protects nitrogenase

3) Fixes nitrogen

4) Decomposes hydrogen peroxide

Choices:

A-__ B-__ C-__ D-__

Explanation: Nitrogenase fixes nitrogen (A-3), leg haemoglobin protects nitrogenase (B-2), catalase decomposes H₂O₂ (C-4), glutamate dehydrogenase assimilates ammonia (D-1). Correct matches: A-3, B-2, C-4, D-1.

9. Fill in the Blanks / Completion MCQ:

The protein that protects nitrogenase in legume nodules is __________.

a) Catalase

b) Leg haemoglobin

c) Transaminase

d) Glutamate dehydrogenase

Explanation: Leg haemoglobin binds oxygen in root nodules, maintaining a low oxygen environment that preserves nitrogenase activity for effective nitrogen fixation. Correct answer is b) Leg haemoglobin.

10. Choose the correct statements MCQ (Statement I & II):

Statement I: Nitrogenase catalyzes nitrogen fixation.

Statement II: Leg haemoglobin is required to protect nitrogenase from oxygen.

a) Both I and II are correct

b) Only I is correct

c) Only II is correct

d) Both are incorrect

Explanation: Nitrogenase fixes atmospheric nitrogen, and leg haemoglobin protects it from oxygen in root nodules. Both statements are correct, reflecting the coordinated mechanism for nitrogen fixation in legumes. Correct answer is a) Both I and II are correct. 

Topic: Amphibolic Pathway and Energy Metabolism ; Subtopic: Role of Porins, Leghemoglobin, and H+ Accumulation

Keyword Definitions:

• Porins: Large protein channels present in the outer membrane of mitochondria that allow free movement of small molecules like ions and metabolites.

• Leghemoglobin: An oxygen-binding pigment found in root nodules of leguminous plants that facilitates oxygen supply to nitrogen-fixing bacteria.

• Thylakoid: Membranous sacs in chloroplasts where light-dependent reactions occur, leading to H+ accumulation inside their lumen.

• Amphibolic Pathway: A biochemical pathway that functions both catabolically and anabolically, like the Krebs cycle in respiration.

• Respiration: A cellular process that converts biochemical energy from nutrients into ATP, involving glycolysis, Krebs cycle, and electron transport chain.

Lead Question – 2022 (Ganganagar)
Match List-I with List-II:
List-I            List-II
(a) Porins            (i) Pink coloured nodules
(b) Leghemoglobin       (ii) Lumen of thylakoid
(c) H+ Accumulation      (iii) Amphibolic pathway
(d) Respiration          (iv) Huge pores in outer membrane of mitochondria

Choose the correct answer from the options given below:
(a) (b) (c) (d)
1. (ii) (i) (iv) (iii)
2. (iv) (i) (ii) (iii)
3. (iii) (iv) (ii) (i)
4. (ii) (iv) (i) (iii)

Explanation:
The correct answer is option 2: (a)–(iv), (b)–(i), (c)–(ii), (d)–(iii). Porins are large protein pores in the outer mitochondrial membrane allowing metabolite transport. Leghemoglobin is a pink pigment in root nodules aiding nitrogen fixation. H+ accumulation occurs in thylakoid lumen during photosynthesis, and respiration is an amphibolic pathway involving both energy release and biosynthesis.

1. Single Correct Answer Type
Porins are mainly present in which organelle of eukaryotic cells?
1. Chloroplast
2. Mitochondrion
3. Nucleus
4. Ribosome
Explanation: Porins are large protein channels found in the outer mitochondrial membrane, allowing free passage of small metabolites like ATP, ADP, and ions. They maintain exchange between the cytosol and mitochondria, supporting respiration and energy metabolism. Thus, option 2 is correct, as mitochondria contain porins for efficient transport regulation.

2. Single Correct Answer Type
Leghemoglobin plays an important role in nitrogen fixation by:
1. Releasing oxygen to bacteria
2. Preventing oxygen poisoning of nitrogenase
3. Acting as a carbon source
4. Providing ATP for nitrogenase
Explanation: Leghemoglobin binds oxygen, maintaining a low but steady oxygen concentration inside root nodules. This prevents oxygen inhibition of nitrogenase enzyme while ensuring respiratory ATP synthesis for nitrogen fixation. Hence, option 2 is correct, as leghemoglobin acts as an oxygen buffer promoting efficient nitrogen fixation in legumes.

3. Single Correct Answer Type
H+ accumulation in the lumen of thylakoids occurs during:
1. Glycolysis
2. Light-dependent reactions
3. Calvin cycle
4. Photorespiration
Explanation: During light-dependent reactions of photosynthesis, protons (H+) accumulate inside the thylakoid lumen due to water splitting and electron transport chain activity. This proton gradient drives ATP synthesis through ATP synthase in photophosphorylation. Hence, option 2 is correct as it explains proton motive force formation during photosynthetic reactions.

4. Single Correct Answer Type
Which of the following statements about respiration is true?
1. It is only a catabolic process.
2. It produces ATP without oxidation.
3. It is an amphibolic process.
4. It occurs only in plants.
Explanation: Respiration is an amphibolic process as it functions both catabolically (breaking down glucose to release energy) and anabolically (providing intermediates for biosynthesis). The Krebs cycle acts as a central link between metabolism and biosynthesis. Hence, option 3 is correct as respiration integrates both anabolic and catabolic roles.

5. Single Correct Answer Type
The pink color of root nodules in leguminous plants is due to:
1. Anthocyanin
2. Chlorophyll
3. Leghemoglobin
4. Carotenoid
Explanation: Leghemoglobin, a red-colored oxygen-binding protein similar to animal hemoglobin, imparts a pink coloration to root nodules in leguminous plants. It regulates oxygen supply to nitrogen-fixing bacteria, preventing nitrogenase inactivation. Thus, option 3 is correct as leghemoglobin plays a dual role in oxygen management and symbiotic nitrogen fixation.

6. Single Correct Answer Type
Which of the following is known as the site of oxidative phosphorylation?
1. Thylakoid membrane
2. Mitochondrial inner membrane
3. Cytoplasm
4. Nuclear envelope
Explanation: Oxidative phosphorylation occurs on the inner mitochondrial membrane, where the electron transport chain operates to generate ATP. The proton gradient across this membrane drives ATP synthesis via ATP synthase. Therefore, option 2 is correct, representing mitochondria as the powerhouse of the cell responsible for energy production.

7. Assertion-Reason Type
Assertion (A): Respiration is both a catabolic and anabolic pathway.
Reason (R): Intermediates of the Krebs cycle participate in biosynthesis of amino acids and fats.
1. Both (A) and (R) are correct and (R) explains (A).
2. Both (A) and (R) are correct but (R) does not explain (A).
3. (A) is correct but (R) is incorrect.
4. (A) is incorrect but (R) is correct.
Explanation: Respiration is an amphibolic process since its intermediates such as α-ketoglutarate and oxaloacetate act as precursors for biosynthetic pathways. Hence, both (A) and (R) are correct and (R) properly explains (A). The correct answer is option 1, showing integration of energy and biosynthesis in metabolism.

8. Matching Type
Match the organelle with its function:
A. Mitochondria – (i) ATP synthesis
B. Chloroplast – (ii) Photosynthesis
C. Nucleus – (iii) Genetic control
D. Ribosome – (iv) Protein synthesis
Options:
1. A-(i), B-(ii), C-(iii), D-(iv)
2. A-(ii), B-(i), C-(iv), D-(iii)
3. A-(iii), B-(ii), C-(i), D-(iv)
4. A-(iv), B-(iii), C-(ii), D-(i)
Explanation: Mitochondria produce ATP, chloroplasts carry out photosynthesis, nucleus stores genetic material, and ribosomes synthesize proteins. Hence, option 1 is correct, as each organelle performs a unique but interrelated role in maintaining cellular energy, metabolism, and regulation essential for life processes.

9. Fill in the Blanks Type
Porins are present in the _______ membrane of mitochondria.
1. Inner
2. Outer
3. Cristae
4. Matrix
Explanation: Porins are located in the outer membrane of mitochondria, forming large aqueous channels that allow diffusion of ions and metabolites. They facilitate communication between the cytosol and mitochondrial intermembrane space. Hence, option 2 is correct, as outer membrane porins are essential for metabolic exchange and transport regulation.

10. Choose the Correct Statements Type
Statement I: H+ accumulation occurs in the lumen of thylakoids during light reaction.
Statement II: Respiration is exclusively a catabolic pathway.
1. Both statements are correct.
2. Both statements are incorrect.
3. Statement I is correct, Statement II is incorrect.
4. Statement I is incorrect, Statement II is correct.
Explanation: H+ accumulation indeed occurs inside the thylakoid lumen during light reactions of photosynthesis, while respiration is an amphibolic pathway, not purely catabolic. Hence, Statement I is correct and Statement II is incorrect. The correct answer is option 3, explaining both processes’ functional interdependence in cellular metabolism.

Subtopic: Immunosuppressive Agents

Keyword Definitions:
• Immunosuppressive agents: Substances that lower the body’s immune response, useful in organ transplantation.
• Cyclosporin A: A bioactive compound used to suppress immune response and prevent transplant rejection.
• Trichoderma polysporum: A fungus responsible for the industrial production of cyclosporin A.
• Aspergillus niger: A fungus used in citric acid production.
• Clostridium butylicum: A bacterium producing butyric acid.
• Fermentation: Process by which microorganisms convert organic compounds into useful products.
• Antibiotics: Microbial metabolites that inhibit or kill other microorganisms.
• Industrial microbiology: Branch of microbiology dealing with microbial production of useful compounds.
• Secondary metabolites: Non-essential microbial products with commercial importance.
• Transplant rejection: Immune reaction against transplanted organs or tissues.

Lead Question (2022):
Identify the microorganism which is responsible for the production of an immunosuppressive molecule cyclosporin A:
(1) Clostridum butylicum
(2) Aspergillus niger
(3) Streptococcus cerevisiae
(4) Trichoderma polysporum

Explanation: The correct answer is (4). Cyclosporin A is an immunosuppressive molecule produced by the fungus Trichoderma polysporum. It is used to prevent organ transplant rejection by suppressing the immune response, specifically by inhibiting the activation of T-lymphocytes responsible for immune rejection reactions in transplant patients.

Guessed MCQs:

1. Single Correct Answer:
Which of the following microorganisms is used for commercial production of citric acid?
(a) Penicillium notatum
(b) Aspergillus niger
(c) Streptococcus lactis
(d) Trichoderma polysporum
Explanation: The correct answer is (b). Aspergillus niger is a filamentous fungus extensively used in the industrial fermentation process for large-scale production of citric acid, an organic acid used in food preservation and pharmaceuticals.

2. Single Correct Answer:
Which microorganism produces butyric acid?
(a) Rhizobium
(b) Clostridium butylicum
(c) Saccharomyces cerevisiae
(d) Lactobacillus
Explanation: The correct answer is (b). Clostridium butylicum is an anaerobic bacterium that produces butyric acid through fermentation, used in the manufacture of biofuels and solvents such as acetone and butanol.

3. Single Correct Answer:
Which enzyme is obtained from Streptococcus used in medical applications?
(a) Lipase
(b) Streptokinase
(c) Lactase
(d) Protease
Explanation: The correct answer is (b). Streptokinase, produced by Streptococcus bacteria, is used to dissolve blood clots in myocardial infarction and pulmonary embolism by converting plasminogen into active plasmin, an enzyme that degrades fibrin clots.

4. Assertion-Reason MCQ:
Assertion (A): Cyclosporin A is used to suppress immunity during organ transplantation.
Reason (R): It inhibits activation of helper T-cells.
(a) Both A and R are correct and R explains A
(b) Both A and R are correct but R does not explain A
(c) A is correct, R is incorrect
(d) A is incorrect, R is correct
Explanation: The correct answer is (a). Cyclosporin A prevents transplant rejection by specifically inhibiting helper T-cell activation, thereby reducing the immune system’s response against the transplanted organ.

5. Single Correct Answer:
Which fungus is used in the production of penicillin?
(a) Penicillium notatum
(b) Aspergillus niger
(c) Trichoderma viride
(d) Rhizopus stolonifer
Explanation: The correct answer is (a). Penicillium notatum produces penicillin, the first antibiotic discovered by Alexander Fleming, which inhibits bacterial cell wall synthesis and is widely used to treat bacterial infections.

6. Single Correct Answer:
Which of the following is an example of bioactive molecule used in medicine?
(a) Cyclosporin A
(b) Ethanol
(c) Lactic acid
(d) Citric acid
Explanation: The correct answer is (a). Cyclosporin A is a bioactive molecule derived from fungi, acting as an immunosuppressive drug to prevent rejection in organ transplantation and autoimmune diseases.

7. Matching Type:
Match the microorganism with its product:
Column A
1. Trichoderma polysporum
2. Aspergillus niger
3. Clostridium butylicum
4. Penicillium notatum
Column B
A. Cyclosporin A
B. Citric acid
C. Butyric acid
D. Penicillin
(a) 1-A, 2-B, 3-C, 4-D
(b) 1-B, 2-D, 3-A, 4-C
(c) 1-C, 2-A, 3-B, 4-D
(d) 1-A, 2-C, 3-B, 4-D
Explanation: The correct answer is (a). Trichoderma produces cyclosporin A, Aspergillus produces citric acid, Clostridium produces butyric acid, and Penicillium produces penicillin—all key microbial products in medicine and industry.

8. Fill in the Blanks:
Cyclosporin A is produced by the fungus ________.
(a) Aspergillus niger
(b) Clostridium butylicum
(c) Trichoderma polysporum
(d) Penicillium notatum
Explanation: The correct answer is (c). Cyclosporin A, produced by Trichoderma polysporum, suppresses immune response and is used in organ transplant patients to prevent rejection reactions by inhibiting T-cell activation.

9. Single Correct Answer:
Which of the following microbial products is not an antibiotic?
(a) Penicillin
(b) Streptomycin
(c) Cyclosporin A
(d) Tetracycline
Explanation: The correct answer is (c). Cyclosporin A is not an antibiotic; it is an immunosuppressive molecule that prevents immune rejection during organ transplantation by suppressing helper T-cell activation.

10. Choose the correct statements:
(a) Cyclosporin A suppresses immunity.
(b) It is produced by Trichoderma polysporum.
(c) It is used in organ transplantation.
(d) It kills bacteria directly.
Explanation: The correct answer is (a), (b), and (c). Cyclosporin A is produced by Trichoderma polysporum and is used as an immunosuppressant during organ transplants, not as an antibacterial compound.

Topic: Nitrogen Fixation
Subtopic: Root Nodules in Actinorhizal Plants

Keyword Definitions:

• Alnus: A genus of trees forming symbiotic nitrogen-fixing nodules with actinobacteria.

• Frankia: Nitrogen-fixing actinobacteria forming root nodules in actinorhizal plants like Alnus.

• Rhizobium: Nitrogen-fixing bacteria forming nodules in leguminous plants.

• Rhodospirillum: Free-living nitrogen-fixing photosynthetic bacteria, not associated with Alnus roots.

• Beijernuckia: Free-living nitrogen-fixing bacteria, not symbiotic in Alnus nodules.

• Nitrogen fixation: Conversion of atmospheric nitrogen into ammonia or organic nitrogen compounds usable by plants.

• Root nodules: Specialized plant root structures hosting nitrogen-fixing bacteria.

• Actinorhizal plants: Non-leguminous plants forming symbiotic nodules with Frankia.

• Symbiosis: Close association between two organisms providing mutual benefit.

• Ammonia: Product of nitrogen fixation used for plant metabolism.

Lead Question (2022)
Which one of the following produces nitrogen fixing nodules on the roots of Alnus ?
(1) Frankia
(2) Rhodospirillum
(3) Beijernuckia
(4) Rhizobium

Explanation:
Alnus, an actinorhizal plant, forms nitrogen-fixing root nodules with the actinobacterium Frankia. Rhizobium nodulates legumes, Rhodospirillum and Beijernuckia are free-living nitrogen-fixing bacteria. Frankia provides ammonia for the plant’s growth, enhancing nitrogen availability. Correct answer is (1).

1. Single Correct Answer MCQ:
Which type of symbiosis occurs between Alnus and Frankia?
(1) Parasitism
(2) Mutualism
(3) Commensalism
(4) Competition

Explanation:
The Alnus-Frankia association is mutualistic: Frankia fixes nitrogen benefiting the plant, while receiving carbohydrates and shelter from the plant. Parasitism or competition does not occur. Correct answer is (2).

2. Single Correct Answer MCQ:
Frankia nodules in Alnus roots are primarily located in:
(1) Leaves
(2) Stems
(3) Root cortex
(4) Flowers

Explanation:
Frankia infects the root cortex of Alnus, forming nodules where nitrogen fixation occurs. Leaves, stems, or flowers are not sites for symbiotic nodules. Correct answer is (3).

3. Single Correct Answer MCQ:
The nitrogen fixed by Frankia is converted to:
(1) Nitrate
(2) Ammonia
(3) Nitrite
(4) Urea

Explanation:
Frankia converts atmospheric nitrogen into ammonia, which is then assimilated by Alnus into amino acids. Nitrate or nitrite is not the primary immediate product in actinorhizal nodules. Correct answer is (2).

4. Single Correct Answer MCQ:
Alnus belongs to which plant family known for actinorhizal nodulation?
(1) Betulaceae
(2) Fabaceae
(3) Rosaceae
(4) Myrtaceae

Explanation:
Alnus belongs to the Betulaceae family and forms actinorhizal nodules with Frankia. Fabaceae forms Rhizobium nodules, Rosaceae and Myrtaceae do not form symbiotic nitrogen-fixing nodules. Correct answer is (1).

5. Single Correct Answer MCQ:
Which other actinorhizal plant forms nodules with Frankia?
(1) Casuarina
(2) Glycine
(3) Pisum
(4) Zea

Explanation:
Casuarina, like Alnus, forms nodules with Frankia. Glycine and Pisum are legumes with Rhizobium, and Zea is a non-nodulating cereal. Correct answer is (1).

6. Single Correct Answer MCQ:
Which bacterial genus forms nodules on legumes?
(1) Frankia
(2) Rhizobium
(3) Beijernuckia
(4) Azotobacter

Explanation:
Rhizobium forms root nodules in leguminous plants for nitrogen fixation. Frankia nodulates actinorhizal plants, Beijernuckia and Azotobacter are free-living nitrogen fixers. Correct answer is (2).

7. Assertion-Reason MCQ:
Assertion (A): Frankia provides nitrogen to Alnus.
Reason (R): Frankia lives freely in soil and does not form nodules.
Options:
(1) Both A and R correct, R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both A and R incorrect

Explanation:
Frankia provides nitrogen to Alnus through nodules. The reason is incorrect since Frankia forms symbiotic nodules rather than living freely. Correct answer is (2).

8. Matching Type MCQ:
Match the bacterium with plant type:
A. Frankia — 1. Legumes
B. Rhizobium — 2. Actinorhizal
C. Beijernuckia — 3. Free-living
D. Azotobacter — 4. Free-living
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–3, D–4
(3) A–2, B–3, C–1, D–4
(4) A–3, B–1, C–2, D–4

Explanation:
Frankia associates with actinorhizal plants (2), Rhizobium with legumes (1), Beijernuckia and Azotobacter are free-living (3, 4). Correct answer is (1).

9. Fill in the Blanks MCQ:
Nitrogen-fixing nodules in Alnus are primarily formed by ________.
(1) Rhizobium
(2) Frankia
(3) Azotobacter
(4) Cyanobacteria

Explanation:
Frankia infects Alnus roots forming nitrogen-fixing nodules. Rhizobium nodulates legumes, Azotobacter is free-living, Cyanobacteria are aquatic nitrogen fixers. Correct answer is (2).

10. Choose the correct statements MCQ:
(a) Frankia nodulates Alnus roots
(b) Rhizobium nodulates legumes
(c) Beijernuckia forms free-living nodules on Alnus
(d) Nitrogen fixation enriches plant nitrogen content
Options:
(1) a, b, d only
(2) a, c, d only
(3) a, b, c only
(4) b, c, d only

Explanation:
Frankia nodulates Alnus (a), Rhizobium nodulates legumes (b), nitrogen fixation enriches plant nitrogen (d). Beijernuckia does not form nodules on Alnus. Correct answer is (1).

Subtopic: Microbial Production of Organic Acids

• Aspergillus niger: Filamentous fungus used industrially to produce citric acid.

• Acetobacter aceti: Bacterium that oxidizes ethanol to acetic acid.

• Clostridium butylicum: Anaerobic bacterium producing butyric acid via fermentation.

• Lactobacillus: Lactic acid-producing bacterium used in dairy fermentation.

• Organic Acids: Acidic compounds with carboxyl groups, produced by microbes for food and industrial processes.

• Fermentation: Microbial conversion of sugars into acids, gases, or alcohol under anaerobic conditions.

• Industrial Microbiology: Use of microbes to produce commercially important products like acids, antibiotics, and enzymes.

• Citric Acid: A tricarboxylic acid widely used in food and beverages, primarily produced by Aspergillus niger.

• Acetic Acid: Produced via oxidation of ethanol by Acetobacter species; used in vinegar production.

• Lactic Acid: Produced by Lactobacillus species; used in yogurt, cheese, and pharmaceuticals.

• Butyric Acid: Produced by Clostridium species; used in food flavoring and chemical industry.

Lead Question - 2021

Match List - I with List - II.
List - I List - II
(a) Aspergillus niger (i) Acetic Acid
(b) Acetobacter aceti (ii) Lactic Acid
(c) Clostridium butylicum (iii) Citric Acid
(d) Lactobacillus (iv) Butyric Acid
Choose the correct answer from the options given below:

1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
3. (a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
4. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

Explanation: Aspergillus niger produces citric acid, Acetobacter aceti produces acetic acid, Clostridium butylicum produces butyric acid, and Lactobacillus produces lactic acid. Correct pairing ensures accurate identification of microbial products in industrial microbiology. Answer: (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii).

1. Single Correct Answer MCQ: Which microbe is primarily used for commercial citric acid production?
Options:
A. Lactobacillus
B. Clostridium butylicum
C. Aspergillus niger
D. Acetobacter aceti

Explanation: Aspergillus niger is a filamentous fungus widely used in industrial fermentation to produce citric acid for food, beverages, and pharmaceuticals. Other microbes produce different acids. Answer: Aspergillus niger.

2. Single Correct Answer MCQ: Acetobacter aceti is industrially important for producing:
Options:
A. Citric acid
B. Lactic acid
C. Acetic acid
D. Butyric acid

Explanation: Acetobacter aceti oxidizes ethanol to produce acetic acid, commonly used in vinegar production. This bacterium does not produce citric, lactic, or butyric acids. Answer: Acetic acid.

3. Single Correct Answer MCQ: Which bacterium produces butyric acid during fermentation?
Options:
A. Lactobacillus
B. Clostridium butylicum
C. Acetobacter aceti
D. Aspergillus niger

Explanation: Clostridium butylicum is an anaerobic bacterium that produces butyric acid via fermentation. It does not produce lactic, citric, or acetic acids. Answer: Clostridium butylicum.

4. Single Correct Answer MCQ: Lactic acid production is characteristic of:
Options:
A. Acetobacter
B. Lactobacillus
C. Clostridium
D. Aspergillus

Explanation: Lactobacillus produces lactic acid in dairy fermentation and industrial applications. Other microbes produce different acids. Answer: Lactobacillus.

5. Single Correct Answer MCQ: Industrial production of organic acids mainly uses:
Options:
A. Fungi and bacteria
B. Algae
C. Protozoa
D. Viruses

Explanation: Fungi and bacteria are used for commercial production of citric, acetic, lactic, and butyric acids. Algae, protozoa, and viruses are not suitable for large-scale organic acid production. Answer: Fungi and bacteria.

6. Single Correct Answer MCQ: Which acid is produced from ethanol oxidation?
Options:
A. Citric acid
B. Acetic acid
C. Butyric acid
D. Lactic acid

Explanation: Oxidation of ethanol by Acetobacter produces acetic acid, a key process in vinegar production. Other acids are produced via different pathways. Answer: Acetic acid.

7. Assertion-Reason MCQ:
Assertion (A): Aspergillus niger is used industrially for citric acid.
Reason (R): It ferments sugar under aerobic conditions to produce citric acid.
Options:
A. Both A and R true, R correct explanation
B. Both A and R true, R not correct explanation
C. A true, R false
D. A false, R true

Explanation: Aspergillus niger ferments sugars aerobically to produce citric acid, widely used industrially. The reason correctly explains the assertion. Answer: Both A and R true, R correct explanation.

8. Matching Type MCQ:
Column I: 1. Citric acid 2. Acetic acid 3. Lactic acid 4. Butyric acid
Column II: A. Clostridium butylicum B. Lactobacillus C. Aspergillus niger D. Acetobacter aceti
Options:
A. 1-C, 2-D, 3-B, 4-A
B. 1-D, 2-B, 3-C, 4-A
C. 1-A, 2-C, 3-D, 4-B
D. 1-B, 2-A, 3-D, 4-C

Explanation: Correct matching: Citric acid – Aspergillus niger, Acetic acid – Acetobacter aceti, Lactic acid – Lactobacillus, Butyric acid – Clostridium butylicum. Answer: 1-C, 2-D, 3-B, 4-A.

9. Fill in the Blank MCQ: _______ produces lactic acid in dairy fermentation.
Options:
A. Aspergillus niger
B. Lactobacillus
C. Acetobacter aceti
D. Clostridium butylicum

Explanation: Lactobacillus converts sugars to lactic acid during dairy and industrial fermentation. Other microbes produce different acids. Answer: Lactobacillus.

10. Choose the Correct Statements MCQ:
1. Aspergillus niger produces citric acid
2. Acetobacter aceti produces acetic acid
3. Clostridium butylicum produces lactic acid
4. Lactobacillus produces lactic acid
Options:
A. 1, 2, 4 only
B. 1, 3 only
C. 2, 3 only
D. 1, 2, 3, 4

Explanation: Statements 1, 2, and 4 are correct. Aspergillus niger produces citric acid, Acetobacter aceti produces acetic acid, Lactobacillus produces lactic acid. Clostridium butylicum produces butyric acid, not lactic acid. Answer: 1, 2, 4 only.

Topic: Microbes in Nitrogen Cycle
Subtopic: Role of Bacteria in Nitrogen Transformations

Keyword Definitions:

• Nitrococcus: Bacterium that converts ammonia to nitrite in the nitrogen cycle.

• Rhizobium: Symbiotic nitrogen-fixing bacterium found in legume root nodules.

• Thiobacillus: Free-living bacterium responsible for denitrification process.

• Nitrobacter: Bacterium that converts nitrite to nitrate in the soil.

• Nitrogen fixation: Conversion of atmospheric nitrogen into ammonia by microbes.

• Denitrification: Reduction of nitrates to nitrogen gas by soil bacteria.

Lead Question - 2021
Match Column - I with Column - II.

Column - I      Column - II
(a) Nitrococcus      (i) Denitrification
(b) Rhizobium      (ii) Conversion of ammonia to nitrite
(c) Thiobacillus     (iii) Conversion of nitrite to nitrate
(d) Nitrobacter     (iv) Atmospheric nitrogen to ammonia

Choose the correct answer from options given below.
(a) (b) (c) (d)
(1) (i) (ii) (iii) (iv)
(2) (iii) (i) (iv) (ii)
(3) (iv) (iii) (ii) (i)
(4) (ii) (iv) (i) (iii)

Explanation: Nitrococcus converts ammonia to nitrite, Rhizobium fixes atmospheric nitrogen, Thiobacillus performs denitrification, and Nitrobacter converts nitrite to nitrate. Thus, the correct matching is (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii). The correct answer is (4).

1. Which bacterium converts nitrite (NO₂⁻) into nitrate (NO₃⁻)?
(1) Nitrococcus
(2) Nitrobacter
(3) Thiobacillus
(4) Rhizobium

Explanation: Nitrobacter is a nitrifying bacterium that oxidizes nitrite to nitrate. This step is crucial in the nitrogen cycle for providing plants with usable nitrate. Thus, the correct answer is (2) Nitrobacter.

2. Which of the following bacteria is symbiotic and helps in biological nitrogen fixation?
(1) Nitrococcus
(2) Azotobacter
(3) Rhizobium
(4) Thiobacillus

Explanation: Rhizobium forms symbiotic associations with legume roots, fixing atmospheric nitrogen into ammonia for plant use. It is the classic example of symbiotic nitrogen-fixing bacteria. Thus, the correct answer is (3) Rhizobium.

3. Assertion (A): Denitrification reduces soil fertility.
Reason (R): Denitrification converts nitrates into gaseous nitrogen.
(1) Both A and R are true, and R explains A.
(2) Both A and R are true, but R does not explain A.
(3) A is true, R is false.
(4) A is false, R is true.

Explanation: Denitrification reduces soil fertility because it depletes nitrate, converting it into gaseous nitrogen. Both assertion and reason are true, and the reason correctly explains the assertion. Thus, the correct answer is (1).

4. Match the following bacteria with their role:
A. Rhizobium
B. Nitrococcus
C. Nitrobacter
D. Thiobacillus

(1) A–Nitrogen fixation, B–Ammonia to nitrite, C–Nitrite to nitrate, D–Denitrification
(2) A–Denitrification, B–Nitrogen fixation, C–Ammonia to nitrite, D–Nitrite to nitrate
(3) A–Nitrite to nitrate, B–Denitrification, C–Nitrogen fixation, D–Ammonia to nitrite
(4) A–Ammonia to nitrite, B–Nitrogen fixation, C–Denitrification, D–Nitrite to nitrate

Explanation: Rhizobium fixes nitrogen, Nitrococcus oxidizes ammonia to nitrite, Nitrobacter oxidizes nitrite to nitrate, and Thiobacillus performs denitrification. The correct answer is (1).

5. Fill in the blank:
__________ is responsible for the conversion of ammonia (NH₃) into nitrite (NO₂⁻).
(1) Nitrococcus
(2) Nitrobacter
(3) Thiobacillus
(4) Rhizobium

Explanation: Nitrococcus is an ammonia-oxidizing bacterium that converts ammonia into nitrite, an important step in the nitrification process of the nitrogen cycle. Thus, the correct answer is (1) Nitrococcus.

6. Which step of the nitrogen cycle is carried out by Thiobacillus?
(1) Nitrogen fixation
(2) Ammonia to nitrite conversion
(3) Denitrification
(4) Nitrite to nitrate conversion

Explanation: Thiobacillus is a denitrifying bacterium that reduces nitrates into gaseous nitrogen or nitrous oxide, leading to nitrogen loss from soil. Thus, the correct answer is (3) Denitrification.

7. Choose the correct statements about nitrogen-fixing bacteria:
(1) Rhizobium is symbiotic.
(2) Azotobacter is free-living.
(3) Nitrobacter fixes nitrogen.
(4) Nitrococcus performs nitrification.
(1) 1 and 2 only
(2) 2 and 3 only
(3) 1, 2 and 4 only
(4) 1, 2, 3 and 4

Explanation: Rhizobium is symbiotic, Azotobacter is free-living nitrogen-fixer, and Nitrococcus participates in nitrification. Nitrobacter does not fix nitrogen but converts nitrite to nitrate. Thus, the correct answer is (3).

8. Which bacterium helps in symbiotic nitrogen fixation in legumes?
(1) Nitrococcus
(2) Nitrobacter
(3) Thiobacillus
(4) Rhizobium

Explanation: Rhizobium forms root nodules in legume plants and fixes atmospheric nitrogen into ammonia, enriching soil fertility. Thus, the correct answer is (4) Rhizobium.

9. Which group of bacteria is directly responsible for nitrification?
(1) Nitrobacter and Nitrococcus
(2) Rhizobium and Thiobacillus
(3) Azotobacter and Clostridium
(4) Pseudomonas and Thiobacillus

Explanation: Nitrification is the biological oxidation of ammonia to nitrite (Nitrococcus) and nitrite to nitrate (Nitrobacter). These two are the primary nitrifying bacteria. Thus, the correct answer is (1).

10. Which step does not involve any nitrifying or denitrifying bacteria?
(1) Conversion of ammonia to nitrite
(2) Conversion of nitrite to nitrate
(3) Nitrogen fixation by Rhizobium
(4) Photosynthesis by cyanobacteria

Explanation: Photosynthesis by cyanobacteria produces oxygen and organic compounds, not directly linked to nitrification or denitrification. Nitrococcus, Nitrobacter, and Thiobacillus handle nitrogen conversions, while Rhizobium fixes nitrogen. Thus, the correct answer is (4).

Topic: Microbial Metabolites and Drugs
Subtopic: Immunosuppressive Agents

Keyword Definitions:

• Cyclosporin A: A cyclic peptide used as an immunosuppressant in organ transplantation.

• Immunosuppression: Reduction of immune system activity to prevent rejection of transplanted organs.

• Monascus purpureus: Fungus used in red yeast rice production, known for pigment and metabolite production.

• Saccharomyces cerevisiae: Baker's yeast used in fermentation and biotechnology.

• Penicillium notatum: Fungus producing penicillin, an antibiotic.

• Trichoderma polysporum: Fungus known for producing enzymes and antifungal compounds.

• Microbial metabolites: Bioactive compounds produced by microbes for medical or industrial use.

• Immunosuppressive drugs: Agents that decrease the immune response.

• Organ transplantation: Transfer of an organ from donor to recipient to restore function.

• Biotechnology: Use of living organisms to develop useful products.

• Antibiotics: Compounds produced by microbes to inhibit other microorganisms.

Lead Question - 2020 (COVID Reexam)

Cyclosporin A, used as an immunosuppression agent, is produced from:

1. Monascus purpureus
2. Saccharomyces cerevisiae
3. Penicillium notatum
4. Trichoderma polysporum

Explanation: The correct answer is Trichoderma polysporum. Cyclosporin A is a cyclic peptide immunosuppressant derived from this fungus. It inhibits T-cell activation, preventing organ transplant rejection. Other options like Monascus purpureus, Saccharomyces cerevisiae, and Penicillium notatum do not produce Cyclosporin A, though they produce other valuable metabolites for medical and industrial use.

1. Chapter: Microbes in Medicine
Topic: Microbial Metabolites and Drugs
Subtopic: Immunosuppressive Agents

Keyword Definitions:

• Cyclosporin A: Cyclic peptide used to suppress immunity.

• Immunosuppression: Reduction of immune system activity.

• Trichoderma polysporum: Fungus producing Cyclosporin A.

• Monascus purpureus: Fungus producing red pigments.

• Saccharomyces cerevisiae: Baker's yeast used in fermentation.

• Penicillium notatum: Fungus producing penicillin.

• Microbial metabolites: Bioactive compounds from microbes.

• Immunosuppressive drugs: Agents decreasing immune response.

• Organ transplantation: Transfer of organ to restore function.

• Biotechnology: Use of organisms to develop products.

• Antibiotics: Microbe-derived compounds inhibiting microbes.

Q1. Single Correct Answer: Which fungus produces penicillin?
a) Monascus purpureus
b) Saccharomyces cerevisiae
c) Penicillium notatum
d) Trichoderma polysporum

Explanation: The correct answer is Penicillium notatum. This fungus produces penicillin, the first discovered antibiotic, which inhibits bacterial cell wall synthesis. Other fungi like Trichoderma polysporum produce immunosuppressants, Monascus purpureus produces pigments, and Saccharomyces cerevisiae is used in fermentation, making them unrelated to penicillin production.

Q2. Single Correct Answer: Which microorganism is widely used in baking and brewing?
a) Penicillium notatum
b) Trichoderma polysporum
c) Saccharomyces cerevisiae
d) Monascus purpureus

Explanation: Saccharomyces cerevisiae, also known as baker's yeast, is used in bread, beer, and wine fermentation. It metabolizes sugars to produce ethanol and carbon dioxide. Trichoderma polysporum produces Cyclosporin A, Penicillium notatum produces penicillin, and Monascus purpureus produces pigments. Option (c) is correct.

Q3. Single Correct Answer: Monascus purpureus is mainly used to produce:
a) Antibiotics
b) Red pigments
c) Immunosuppressants
d) Enzymes

Explanation: Monascus purpureus is known for producing red pigments used in food coloring and traditional medicine. It does not produce antibiotics or Cyclosporin A. Trichoderma polysporum produces immunosuppressants, and Penicillium notatum produces antibiotics. Hence, option (b) is correct.

Q4. Single Correct Answer: Cyclosporin A primarily functions by:
a) Killing bacteria
b) Suppressing T-cell activity
c) Enhancing white blood cells
d) Acting as an enzyme

Explanation: Cyclosporin A suppresses T-cell activation, reducing immune responses. It is critical in preventing organ transplant rejection. It does not act as an antibiotic, enzyme, or stimulate immune cells. Option (b) is correct because it targets the immune system selectively, making it an effective immunosuppressive drug.

Q5. Single Correct Answer: Which fungus produces immunosuppressive drugs?
a) Penicillium notatum
b) Monascus purpureus
c) Trichoderma polysporum
d) Saccharomyces cerevisiae

Explanation: Trichoderma polysporum produces Cyclosporin A, an immunosuppressive agent used in transplantation. Penicillium notatum produces penicillin, Monascus purpureus produces pigments, and Saccharomyces cerevisiae is used in fermentation. Therefore, option (c) is correct because it is the source of a clinically important immunosuppressive drug.

Q6. Single Correct Answer: Penicillin inhibits:
a) Virus replication
b) Bacterial cell wall synthesis
c) T-cell activity
d) Fungal growth

Explanation: Penicillin inhibits bacterial cell wall synthesis, leading to lysis of susceptible bacteria. It does not affect viruses, T-cells, or fungi. Penicillium notatum is the source of penicillin. Option (b) is correct as it highlights the antibiotic mechanism of this classical microbial metabolite.

Q7. Assertion-Reason:
Assertion (A): Cyclosporin A is essential in organ transplantation.
Reason (R): It suppresses immune response by inhibiting T-cell activity.

a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true

Explanation: Both the assertion and reason are correct, and the reason explains the assertion. Cyclosporin A prevents organ rejection by suppressing T-cell mediated immunity. This selective immunosuppression makes transplantation safer and more effective. Option (a) is correct, reflecting its clinical importance.

Q8. Matching Type: Match microbes with their products:
Column - I: a) Trichoderma polysporum, b) Penicillium notatum, c) Monascus purpureus
Column - II: i) Penicillin, ii) Cyclosporin A, iii) Red pigments

Options:
1. a-ii, b-i, c-iii
2. a-i, b-ii, c-iii
3. a-iii, b-i, c-ii
4. a-ii, b-iii, c-i

Explanation: Correct match is a-ii, b-i, c-iii. Trichoderma polysporum produces Cyclosporin A, Penicillium notatum produces penicillin, and Monascus purpureus produces red pigments. This demonstrates the distinct metabolites produced by different fungi with medical and industrial applications. Option (1) is correct.

Q9. Fill in the Blanks: ________ inhibits T-cell activity to prevent organ transplant rejection.
a) Penicillin
b) Cyclosporin A
c) Red pigments
d) Saccharomyces cerevisiae

Explanation: Cyclosporin A inhibits T-cell activation, suppressing the immune response and preventing organ transplant rejection. Penicillin is an antibiotic, red pigments are produced by Monascus purpureus, and Saccharomyces cerevisiae is used in fermentation. Therefore, option (b) is correct, highlighting its role as an immunosuppressive drug.

Q10. Choose the correct statements:
1) Trichoderma polysporum produces Cyclosporin A.
2) Penicillium notatum produces penicillin.
3) Saccharomyces cerevisiae is used in baking.
4) Monascus purpureus produces antibiotics.

a) 1, 2, 3
b) 1, 2, 4
c) 2, 3, 4
d) All are correct

Explanation: Statements 1, 2, and 3 are correct. Trichoderma polysporum produces Cyclosporin A, Penicillium notatum produces penicillin, and Saccharomyces cerevisiae is used in baking and brewing. Monascus purpureus produces red pigments, not antibiotics. Therefore, option (a) is correct, summarizing key microbial contributions.

Subtopic: Biocontrol Agents and Symbiotic Microbes

Keyword Definitions:

• Dragonflies: Predatory insects that feed on aphids, mosquitoes and other small pests.

• Bacillus thuringiensis: Bacterial species producing insecticidal toxins effective against lepidopteran pests.

• Glomus: Arbuscular mycorrhizal fungi that enhance phosphorus uptake in plants.

• Baculoviruses: Viruses used as biological pesticides for specific insect pests.

• Biocontrol agents: Organisms used to suppress pest populations naturally.

• Phosphorus absorption: Uptake of phosphorus from soil by symbiotic fungi aiding plant growth.

• Lepidopteran pests: Caterpillars of butterflies and moths that damage crops.

• Aphids: Small sap-sucking insects harmful to plants.

• Insecticidal applications: Use of biological or chemical agents to control insects.

• Symbiotic microbes: Microorganisms living in mutual association with plants.

• Narrow spectrum: Targeting specific pests rather than broad range.

Lead Question - 2020 (COVID Reexam)

Match the following columns and select the correct option:-
Column - I    Column - II

a) Dragonflies    (i) Biocontrol agents of several plant pathogens
b) Bacillus thuringiensis    (ii) Get rid of Aphids and mosquitoes
c) Glomus    (iii) Narrow spectrum insecticidal applications
d) Baculoviruses    (iv) Biocontrol agents of lepidopteran plant pests
            (v) Absorb phosphorus from soil

1. (a)-(iii), (b)-(v), (c)-(iv), (d)-(i)
2. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
3. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(v)
4. (a)-(ii), (b)-(iv), (c)-(v), (d)-(iii)

Explanation: The correct answer is option 4. Dragonflies are predators that help eliminate aphids and mosquitoes (a)-(ii). Bacillus thuringiensis produces narrow spectrum insecticidal toxins effective against lepidopteran pests (b)-(iv). Glomus fungi absorb phosphorus from soil aiding plant nutrition (c)-(v). Baculoviruses target lepidopteran pests specifically (d)-(iii). This matches each organism with its agricultural role precisely.

1. Chapter: Plant Biotechnology and Microbes
Topic: Microbes in Agriculture
Subtopic: Biocontrol Agents and Symbiotic Microbes

Keyword Definitions:

• Biocontrol agents: Organisms used to suppress pest populations naturally.

• Symbiotic microbes: Microorganisms living in mutual association with plants.

• Phosphorus absorption: Uptake of phosphorus from soil by fungi aiding growth.

• Narrow spectrum: Targeting specific pests rather than broad range.

• Lepidopteran pests: Caterpillars harmful to crops.

• Aphids: Small sap-sucking insects.

• Dragonflies: Predatory insects consuming pests.

• Bacillus thuringiensis: Bacteria producing insecticidal toxins.

• Glomus: Mycorrhizal fungi improving nutrient uptake.

• Baculoviruses: Viruses targeting specific insects.

• Insecticidal applications: Biological or chemical pest control.

Q1. Single Correct Answer: Which microbe is used to improve phosphorus uptake in plants?
a) Bacillus thuringiensis
b) Glomus
c) Baculoviruses
d) Dragonflies

Explanation: The correct answer is Glomus. It is an arbuscular mycorrhizal fungus that forms symbiotic associations with roots, enhancing phosphorus absorption from soil, improving plant nutrition, and increasing growth. Unlike Bacillus thuringiensis and Baculoviruses, it does not target insects but aids nutrient uptake in crops efficiently.

Q2. Single Correct Answer: Which of the following targets lepidopteran pests specifically?
a) Glomus
b) Baculoviruses
c) Dragonflies
d) Rhizobium

Explanation: Baculoviruses are viruses used as biocontrol agents against lepidopteran pests. They infect caterpillars of moths and butterflies selectively, causing pest suppression. Other options like Glomus and Dragonflies do not act on these pests. Baculoviruses provide a safe, narrow-spectrum biological control method in agriculture, preventing crop losses.

Q3. Single Correct Answer: Which organism helps control mosquito and aphid populations naturally?
a) Bacillus thuringiensis
b) Glomus
c) Dragonflies
d) Baculoviruses

Explanation: Dragonflies are predatory insects feeding on aphids and mosquitoes. They act as natural biocontrol agents reducing pest numbers without chemicals. Glomus improves nutrients and Baculoviruses target lepidopteran pests. Therefore, Dragonflies (c) are the correct choice for controlling mosquito and aphid populations effectively in integrated pest management systems.

Q4. Single Correct Answer: Bacillus thuringiensis is best known for:
a) Nitrogen fixation
b) Producing insecticidal toxins
c) Phosphorus absorption
d) Killing aphids naturally

Explanation: Bacillus thuringiensis produces crystalline insecticidal toxins targeting lepidopteran pests. These toxins disrupt the gut of caterpillars causing death. It is a narrow-spectrum biological pesticide widely used in crops. It does not fix nitrogen, absorb phosphorus, or directly kill aphids, making option (b) correct.

Q5. Single Correct Answer: Symbiotic fungi like Glomus primarily help plants by:
a) Killing pests
b) Absorbing phosphorus
c) Producing insecticidal toxins
d) Fixing nitrogen

Explanation: Glomus forms arbuscular mycorrhizal associations with plant roots, enhancing phosphorus absorption. This improves plant growth and nutrient availability. It does not produce toxins or fix nitrogen. By improving nutrient uptake, Glomus indirectly strengthens plant resistance, making (b) the correct answer.

Q6. Single Correct Answer: Which of the following is a narrow-spectrum biocontrol agent?
a) Baculoviruses
b) Dragonflies
c) Glomus
d) Rhizobium

Explanation: Baculoviruses are narrow-spectrum viruses targeting lepidopteran pests only. They do not affect other insects, making them highly specific. Dragonflies are broad-spectrum predators. Glomus is symbiotic, aiding nutrient absorption. Therefore, option (a) is correct, representing an efficient, eco-friendly pest management strategy.

Q7. Assertion-Reason:
Assertion (A): Bacillus thuringiensis is widely used in pest control.
Reason (R): It produces toxins specific to insect pests.

a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true

Explanation: Both A and R are true, and the reason correctly explains the assertion. Bacillus thuringiensis produces insecticidal toxins that specifically kill caterpillars and other pests. This specificity makes it widely applicable in agriculture for pest control. Option (a) is correct.

Q8. Matching Type: Match organisms with their roles:
Column - I: a) Dragonflies, b) Baculoviruses, c) Glomus
Column - II: i) Predator, ii) Biocontrol virus, iii) Phosphorus absorption

Options:
1. a-i, b-ii, c-iii
2. a-ii, b-i, c-iii
3. a-iii, b-i, c-ii
4. a-i, b-iii, c-ii

Explanation: Correct match is a-i, b-ii, c-iii. Dragonflies are predators of mosquitoes and aphids, Baculoviruses act as specific biocontrol viruses against lepidopteran pests, and Glomus fungi assist phosphorus absorption in plant roots. This clearly aligns each organism with its ecological or agricultural role.

Q9. Fill in the Blanks: Glomus fungi help plants primarily by ________ from soil.
a) Nitrogen fixation
b) Phosphorus absorption
c) Producing insecticidal toxins
d) Killing pests

Explanation: Glomus fungi form symbiotic associations with plant roots and absorb phosphorus from the soil. This nutrient is critical for plant growth and energy transfer. They do not fix nitrogen or produce insecticidal toxins. Therefore, option (b) phosphorus absorption is correct, making plants healthier and more productive naturally.

Q10. Choose the correct statements:
1) Dragonflies control aphids and mosquitoes.
2) Baculoviruses are narrow-spectrum pest viruses.
3) Glomus absorbs nitrogen for plants.
4) Bacillus thuringiensis targets lepidopteran pests.

a) 1, 2, 4
b) 1, 3, 4
c) 2, 3, 4
d) All are correct

Explanation: Statements 1, 2, and 4 are correct. Dragonflies reduce aphid and mosquito populations. Baculoviruses target specific pests. Bacillus thuringiensis produces toxins against lepidopteran pests. Glomus absorbs phosphorus, not nitrogen. Therefore, option (a) is correct, highlighting the distinct roles of these organisms in agriculture and pest management.

Topic: Industrial Microbiology
Subtopic: Production of Citric Acid

Keyword Definitions:

• Citric Acid: Organic acid widely used in food, beverages, and pharmaceuticals.

• Aspergillus niger: Filamentous fungus used industrially to produce citric acid.

• Lactobacillus sp: Lactic acid-producing bacteria used in fermentation of dairy products.

• Saccharomyces cerevisiae: Yeast used in alcohol and bread fermentation.

• Clostridium bretylium: Anaerobic bacterium known for solvent production.

• Commercial production: Large-scale industrial manufacturing.

• Fermentation: Microbial conversion of substrates into desired products.

• Industrial microbiology: Application of microbes for manufacturing useful products.

Lead Question - 2020 (COVID Reexam)

For the commercial and industrial production of Citric Acid, which of the following microbes is used?

1. Aspergillus niger
2. Lactobacillus sp
3. Saccharomyces cerevisiae
4. Clostridium bretylium

Explanation: Aspergillus niger, a filamentous fungus, is widely used for commercial production of citric acid due to its high yield and efficiency. Other microbes like Lactobacillus produce lactic acid, Saccharomyces cerevisiae produces ethanol, and Clostridium bretylium produces solvents. Correct answer: Option 1.

1. Single Correct Answer MCQ:

Which substrate is commonly used for citric acid production by Aspergillus niger?
1. Glucose
2. Lactose
3. Sucrose
4. Starch

Explanation: Glucose is the preferred substrate for Aspergillus niger in industrial citric acid production. It allows efficient fermentation and high yield. Lactose and starch require additional processing, while sucrose is less commonly used. Answer: Option 1.

2. Single Correct Answer MCQ:

Citric acid production by microbes is an example of:
1. Aerobic fermentation
2. Anaerobic fermentation
3. Photosynthesis
4. Nitrogen fixation

Explanation: Aspergillus niger produces citric acid through aerobic fermentation, requiring oxygen for metabolism. Anaerobic fermentation is typical for alcohol production. Photosynthesis and nitrogen fixation are unrelated microbial processes. Answer: Option 1.

3. Single Correct Answer MCQ:

Which factor increases citric acid yield in Aspergillus niger fermentation?
1. High sugar concentration
2. Low pH
3. Adequate aeration
4. All of the above

Explanation: High sugar concentration, low pH, and proper aeration enhance citric acid yield in Aspergillus niger fermentation. These conditions favor enzyme activity and acid accumulation. Answer: Option 4.

4. Single Correct Answer MCQ:

Citric acid obtained from microbial fermentation is preferred because:
1. Purity is high
2. Production is cost-effective
3. Renewable substrates can be used
4. All of the above

Explanation: Microbial citric acid has high purity, cost-effective production, and can use renewable substrates such as molasses or glucose. These advantages make it preferred over extraction from citrus fruits. Answer: Option 4.

5. Single Correct Answer MCQ:

Which by-product is minimal in Aspergillus niger citric acid production?
1. Oxalic acid
2. Lactic acid
3. Ethanol
4. Acetic acid

Explanation: In citric acid production using Aspergillus niger, oxalic acid formation is minimal under controlled low pH and sugar conditions. Lactic acid, ethanol, and acetic acid are not significant by-products. This ensures high purity of citric acid. Answer: Option 1.

6. Single Correct Answer MCQ:

Industrial fermentation of citric acid is mostly carried out in:
1. Solid-state fermentation
2. Submerged fermentation
3. Anaerobic tanks
4. Photo-bioreactors

Explanation: Submerged fermentation is widely used for citric acid production with Aspergillus niger. It allows better aeration, mixing, and temperature control, leading to higher yields compared to solid-state fermentation. Answer: Option 2.

7. Assertion-Reason MCQ:

Assertion (A): Aspergillus niger is the microbe of choice for citric acid production.
Reason (R): It produces high yield under aerobic, low pH, and sugar-rich conditions.
1. Both A and R true, R correct explanation
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true

Explanation: Aspergillus niger produces citric acid efficiently under aerobic, low pH, and high sugar conditions. These factors explain why it is preferred in industrial production. Both assertion and reason are true, with reason correctly explaining assertion. Answer: Option 1.

8. Matching Type MCQ:

Column I    Column II
(a) Aspergillus niger    (i) Citric acid
(b) Lactobacillus sp    (ii) Lactic acid
(c) Saccharomyces cerevisiae    (iii) Ethanol
(d) Clostridium bretylium    (iv) Solvents

1. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
2. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
4. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)

Explanation: Aspergillus niger produces citric acid, Lactobacillus produces lactic acid, Saccharomyces cerevisiae produces ethanol, and Clostridium bretylium produces solvents. Correct matching: Option 1.

9. Fill in the blanks MCQ:

The filamentous fungus used industrially to produce citric acid is ______.
1. Aspergillus niger
2. Saccharomyces cerevisiae
3. Lactobacillus sp
4. Clostridium bretylium

Explanation: Aspergillus niger is the primary filamentous fungus employed for industrial citric acid production. It efficiently converts glucose into citric acid under controlled fermentation conditions, making it the microbe of choice. Answer: Option 1.

Subtopic: Microbial Metabolites and Their Uses

• Clostridium butylicum: Anaerobic bacterium used in industrial production of butyric acid.

• Trichoderma polysporum: Fungus known for producing cyclosporin-A, an immunosuppressive drug.

• Monascus purpureus: Red mold used in fermentation and production of compounds that lower blood cholesterol.

• Aspergillus niger: Fungus used for industrial production of citric acid.

• Butyric acid: Short-chain fatty acid produced by fermentation, used in chemical industries.

• Cyclosporin-A: Immunosuppressive drug produced by fungi, used in organ transplant patients.

• Citric acid: Organic acid widely used in food and pharmaceutical industries.

• Blood cholesterol lowering agent: Compounds that help reduce cholesterol levels, often derived from Monascus fermentation.

• Industrial microbiology: Branch of microbiology that uses microorganisms for producing useful products.

• Fermentation: Metabolic process converting substrates to useful products using microbes.

• Microbial metabolite: Biochemical produced by microorganisms, either primary or secondary, with industrial application.

Lead Question (2020): Match the following columns and select the correct option:
Column - I | Column - II
(a) Clostridium butylicum - (i) Cyclosporin-A
(b) Trichoderma polysporum - (ii) Butyric Acid
(c) Monascus purpureus - (iii) Citric Acid
(d) Aspergillus niger - (iv) Blood cholesterol lowering agent
Options:
1. a-i, b-ii, c-iv, d-iii
2. a-iv, b-iii, c-ii, d-i
3. a-iii, b-iv, c-ii, d-i
4. a-ii, b-i, c-iv, d-iii

Explanation: Correct answer is 4. Clostridium butylicum produces butyric acid, Trichoderma polysporum produces cyclosporin-A, Monascus purpureus produces blood cholesterol lowering agents, and Aspergillus niger produces citric acid. These microbial metabolites are widely utilized in pharmaceutical and industrial applications.

1. Single Correct Answer MCQ:
Which microbe is used for commercial production of citric acid?
Options:
a. Clostridium butylicum
b. Aspergillus niger
c. Trichoderma polysporum
d. Monascus purpureus

Explanation: Correct answer is b. Aspergillus niger is industrially used to produce citric acid via fermentation. The fungus converts carbohydrates into citric acid efficiently, making it the most widely applied microbial source for citric acid in food and pharmaceutical industries.

2. Single Correct Answer MCQ:
Which microbial product is primarily used as an immunosuppressant?
Options:
a. Butyric acid
b. Cyclosporin-A
c. Citric acid
d. Cholesterol lowering agent

Explanation: Correct answer is b. Cyclosporin-A, produced by Trichoderma polysporum, is an immunosuppressive drug used in organ transplant patients to prevent graft rejection, illustrating the importance of secondary metabolites in medicine.

3. Single Correct Answer MCQ:
Monascus purpureus is mainly utilized to produce:
Options:
a. Citric acid
b. Butyric acid
c. Blood cholesterol lowering agents
d. Cyclosporin-A

Explanation: Correct answer is c. Monascus purpureus is a red mold used in fermentation to produce natural compounds that lower blood cholesterol, showing its industrial and nutraceutical importance.

4. Single Correct Answer MCQ:
Which microbial metabolite is a short-chain fatty acid used in chemical industries?
Options:
a. Citric acid
b. Butyric acid
c. Cyclosporin-A
d. Cholesterol lowering agent

Explanation: Correct answer is b. Clostridium butylicum produces butyric acid, a short-chain fatty acid widely applied in chemical and food industries as a precursor for biofuels, esters, and other chemicals.

5. Single Correct Answer MCQ:
Trichoderma polysporum is industrially significant for producing:
Options:
a. Citric acid
b. Butyric acid
c. Cyclosporin-A
d. Cholesterol lowering agents

Explanation: Correct answer is c. Trichoderma polysporum produces cyclosporin-A, a secondary metabolite used as an immunosuppressive drug, highlighting the role of fungi in pharmaceutical biotechnology.

6. Single Correct Answer MCQ:
Which microbial product is derived from Clostridium butylicum?
Options:
a. Cyclosporin-A
b. Citric acid
c. Butyric acid
d. Blood cholesterol lowering agent

Explanation: Correct answer is c. Clostridium butylicum produces butyric acid via anaerobic fermentation, used in food, pharmaceutical, and chemical industries.

7. Assertion-Reason MCQ:
Assertion (A): Aspergillus niger is used for citric acid production.
Reason (R): Citric acid is synthesized through microbial fermentation of carbohydrates.
Options:
a. Both A and R true, R explains A
b. Both A and R true, R does not explain A
c. A true, R false
d. A false, R true

Explanation: Correct answer is a. Aspergillus niger ferments sugars to produce citric acid, making both assertion and reason true and reason correctly explaining the assertion.

8. Matching Type MCQ:
Match microbe with its product:
(a) Monascus purpureus - (i) Cyclosporin-A
(b) Trichoderma polysporum - (ii) Blood cholesterol lowering agent
(c) Aspergillus niger - (iii) Citric acid
(d) Clostridium butylicum - (iv) Butyric acid
Options:
1. a-ii, b-i, c-iii, d-iv
2. a-i, b-ii, c-iv, d-iii
3. a-iii, b-iv, c-i, d-ii
4. a-iv, b-iii, c-ii, d-i

Explanation: Correct answer is 1. Monascus purpureus produces cholesterol-l

Topic: Microbes in Agriculture and Industry
Subtopic: Biocontrol Agents

• Bacillus thuringiensis: Soil bacterium producing crystal proteins toxic to insect larvae.

• Trichoderma: Fungal biocontrol agent that suppresses plant pathogens through parasitism and antibiosis.

• Baculovirus: Virus used to control insect pests in agriculture.

• Biocontrol agents: Organisms used to suppress pest populations, reducing chemical pesticide use.

• Oscillatoria: Cyanobacterium, not used as biocontrol agent.

• Rhizobium: Nitrogen-fixing bacterium, beneficial to plants but not a pest control agent.

• Nostoc: Cyanobacterium involved in nitrogen fixation.

• Axospirillum: Nitrogen-fixing bacterium.

• Tobacco mosaic virus: Plant pathogen, not a biocontrol agent.

• Nucleopolyhedrovirus: Virus controlling lepidopteran pests.

• Aphids: Plant pests, not biocontrol agents.

Lead Question (2019): Select the correct group of biocontrol agents:
Options:
1. Bacillus thuringiensis, Tobacco mosaic virus, Aphids
2. Trichoderma, Baculovirus, Bacillus thuringiensis
3. Oscillartoria, Rhizobium, Trichoderma
4. Nostoc, Axospirillium, Nucleopolyhedrovirus

Explanation: Correct answer is 2. Trichoderma, Baculovirus, and Bacillus thuringiensis are widely used biocontrol agents. Trichoderma suppresses fungal pathogens, Baculovirus controls insect pests, and B. thuringiensis produces toxins lethal to insects. Other options include pests or non-biocontrol organisms like Rhizobium and Nostoc.

1. Single Correct Answer MCQ:
Which organism is used as a fungal biocontrol agent against plant pathogens?
Options:
a. Trichoderma
b. Bacillus thuringiensis
c. Baculovirus
d. Oscillatoria

Explanation: Correct answer is a. Trichoderma is a fungal biocontrol agent effective against soil-borne pathogens through parasitism and antibiosis. B. thuringiensis and Baculovirus target insects, while Oscillatoria is a cyanobacterium with no pest control activity.

2. Single Correct Answer MCQ:
Which bacterial biocontrol agent produces insecticidal crystal proteins?
Options:
a. Bacillus thuringiensis
b. Rhizobium
c. Trichoderma
d. Nostoc

Explanation: Correct answer is a. Bacillus thuringiensis produces crystalline proteins toxic to insect larvae. Rhizobium and Nostoc are nitrogen-fixing bacteria, while Trichoderma is a fungal biocontrol agent, not bacterial.

3. Single Correct Answer MCQ:
Which virus is used as a biocontrol agent against lepidopteran pests?
Options:
a. Tobacco mosaic virus
b. Baculovirus
c. Nucleopolyhedrovirus
d. Adenovirus

Explanation: Correct answer is b. Baculovirus is widely used for biological control of insect pests in agriculture, particularly lepidopterans. Tobacco mosaic virus is a plant pathogen, Nucleopolyhedrovirus is related but Baculovirus is the general commercial name, and Adenovirus is not used in agriculture.

4. Single Correct Answer MCQ:
Which of the following is NOT a biocontrol agent?
Options:
a. Bacillus thuringiensis
b. Aphids
c. Trichoderma
d. Baculovirus

Explanation: Correct answer is b. Aphids are plant pests and cannot be used as biocontrol agents. B. thuringiensis, Trichoderma, and Baculovirus are effective in controlling specific agricultural pests or pathogens.

5. Single Correct Answer MCQ:
Which fungal biocontrol agent acts by parasitising other fungi?
Options:
a. Trichoderma
b. Bacillus thuringiensis
c. Oscillatoria
d. Nostoc

Explanation: Correct answer is a. Trichoderma parasitizes soil-borne fungi to protect crops. B. thuringiensis targets insects, and Oscillatoria and Nostoc are cyanobacteria, not involved in fungal pest control.

6. Single Correct Answer MCQ:
Baculovirus targets which type of organism?
Options:
a. Fungi
b. Insects
c. Bacteria
d. Plants

Explanation: Correct answer is b. Baculovirus is an insect-specific virus used as a biocontrol agent, especially for lepidopteran pests. It does not target fungi, bacteria, or plants.

7. Assertion-Reason MCQ:
Assertion (A): Bacillus thuringiensis is used for insect control.
Reason (R): It produces crystal proteins toxic to insect larvae.
Options:
a. Both A and R are true, R explains A
b. Both A and R are true, R does not explain A
c. A is true, R is false
d. A is false, R is true

Explanation: Correct answer is a. B. thuringiensis is used as a biocontrol agent because it produces crystalline proteins that are toxic to insect larvae. Both assertion and reason are correct, and the reason directly explains the use of B. thuringiensis in pest management.

8. Matching Type MCQ:
Match the organism with its role:
(a) Trichoderma | (i) Insect control
(b) Baculovirus | (ii) Fungal pathogen control
(c) Bacillus thuringiensis | (iii) Nitrogen fixation
Options:
1. a-ii, b-i, c-iii
2. a-ii, b-i, c-i
3. a-i, b-ii, c-i
4. a-iii, b-ii, c-i

Explanation: Correct answer is 2. Trichoderma controls fungal pathogens (a-ii), Baculovirus controls insect pests (b-i), and B. thuringiensis is also an insect biocontrol agent (c-i). Nitrogen-fixing roles are irrelevant in this context.

9. Fill in the Blanks MCQ:
The bacterium used as a biocontrol agent against lepidopteran pests is ________.
Options:
a. Bacillus thuringiensis
b. Rhizobium
c. Trichoderma
d. Oscillatoria

Explanation: Correct answer is a. Bacillus thuringiensis produces insecticidal crystal proteins used against lepidopteran pests. Rhizobium fixes nitrogen, Trichoderma controls fungi, and Oscillatoria is a cyanobacterium, none used for insect control.

10. Choose the correct statements MCQ:
Select correct statements about biocontrol agents:
i. Trichoderma controls fungal pathogens
ii. Baculovirus controls insect pests
iii. B. thuringiensis targets insect larvae
iv. Aphids are biocontrol agents
Options:
a. i, ii, iii
b. i, iii, iv
c. ii, iii, iv
d. i, ii, iii, iv

Explanation: Correct answer is a. Trichoderma suppresses fungal pathogens, Baculovirus controls insect pests, and B. thuringiensis kills insect larvae. Aphids are plant pests, not biocontrol agents. All three statements correctly describe commercially used biocontrol organisms.

Subtopic: Nitrogen Cycle and Chemosynthesis

Keyword Definitions:

• Thiobacillus: A genus of chemoautotrophic bacteria involved in oxidation of sulfur compounds.

• Nitrogen fixation: Conversion of atmospheric nitrogen into ammonia by microorganisms.

• Chemoautotrophic fixation: Process in which bacteria obtain energy by oxidizing inorganic compounds to fix carbon or nitrogen.

• Nitrification: Oxidation of ammonia to nitrite and then nitrate by bacteria.

• Denitrification: Conversion of nitrates into nitrogen gas by bacteria, releasing it to the atmosphere.

• Bacteria: Microorganisms that can have roles in nutrient cycling and energy transformations.

Lead Question (September 2019):

Thiobacillus is a group of bacteria helpful in carrying out:
(1) Nitrogen fixation
(2) Chemoautotrophic fixation
(3) Nitrification
(4) Denitrification

Explanation: The correct answer is (3) Nitrification. Thiobacillus bacteria oxidize ammonia to nitrites and nitrites to nitrates, playing a crucial role in the nitrogen cycle. NEET UG tests understanding of bacterial roles in nutrient cycles and chemosynthetic energy acquisition mechanisms.

1) Nitrogen-fixing bacteria include:
(1) Rhizobium
(2) Thiobacillus
(3) Nitrosomonas
(4) Pseudomonas

Explanation: The correct answer is (1) Rhizobium. These bacteria form symbiotic associations with legumes and fix atmospheric nitrogen into ammonia. NEET UG often tests distinction between nitrogen-fixing and nitrifying bacteria.

2) Chemoautotrophs obtain energy by:
(1) Photosynthesis
(2) Oxidation of inorganic compounds
(3) Fermentation of sugars
(4) Respiration using organic molecules

Explanation: The correct answer is (2). Chemoautotrophs like Thiobacillus oxidize sulfur or ammonia to obtain energy for metabolism. NEET UG examines understanding of bacterial energy pathways.

3) Nitrification converts ammonia into:
(1) Nitrogen gas
(2) Nitrate
(3) Amino acids
(4) Nitrogen oxide

Explanation: The correct answer is (2) Nitrate. Thiobacillus species oxidize ammonia → nitrite → nitrate. NEET UG tests the stepwise process of nitrogen cycle.

4) Denitrification releases:
(1) Ammonia
(2) Nitrate
(3) Nitrogen gas
(4) Nitrite

Explanation: The correct answer is (3) Nitrogen gas. Denitrifying bacteria convert nitrates to N2, replenishing atmospheric nitrogen. NEET UG tests differentiation between nitrification and denitrification processes.

5) Sulfur-oxidizing bacteria include:
(1) Thiobacillus
(2) Clostridium
(3) Nitrosomonas
(4) Rhizobium

Explanation: The correct answer is (1) Thiobacillus. They oxidize sulfur compounds for energy. NEET UG evaluates the functional diversity of chemoautotrophic bacteria.

6) Role of nitrifying bacteria in soil is:
(1) Produce organic acids
(2) Convert ammonia to nitrate
(3) Decompose cellulose
(4) Fix atmospheric nitrogen

Explanation: The correct answer is (2). Nitrifying bacteria like Nitrosomonas and Nitrobacter oxidize ammonia to nitrate, enriching soil nitrogen. NEET UG tests comprehension of ecological roles of bacteria.

7) Assertion-Reason Type:
Assertion (A): Thiobacillus participates in nitrification.
Reason (R): It oxidizes ammonia to nitrites and nitrates.
(1) A true, R true, R correct explanation
(2) A true, R true, R not explanation
(3) A true, R false
(4) A false, R true

Explanation: The correct answer is (1). Thiobacillus oxidizes ammonia → nitrite → nitrate, performing nitrification. NEET UG often tests causal linkage of bacterial activity and biochemical transformations.

8) Matching Type:
Match bacteria with function:
(a) Rhizobium - (i) Nitrogen fixation
(b) Nitrosomonas - (ii) Ammonia oxidation
(c) Nitrobacter - (iii) Nitrite to nitrate
(d) Thiobacillus - (iv) Sulfur oxidation
Options:
(1) a-i, b-ii, c-iii, d-iv
(2) a-ii, b-i, c-iv, d-iii
(3) a-i, b-iii, c-ii, d-iv
(4) a-iv, b-ii, c-i, d-iii

Explanation: The correct answer is (1). Each bacterium has a specific biochemical function: nitrogen fixation, ammonia oxidation, nitrite conversion, and sulfur oxidation. NEET UG evaluates association of microbes with metabolic roles.

9) Fill in the Blanks:
Bacteria responsible for converting ammonia to nitrite is ______.
(1) Nitrosomonas
(2) Thiobacillus
(3) Rhizobium
(4) Pseudomonas

Explanation: The correct answer is (1) Nitrosomonas. NEET UG tests knowledge of specific genera involved in nitrification steps.

10) Choose the correct statements:
(1) Thiobacillus is chemoautotrophic
(2) Thiobacillus participates in nitrification
(3) Rhizobium fixes nitrogen
(4) Denitrifying bacteria release nitrogen gas
Options:
(1) 1, 2, 3, 4
(2) 1, 2, 3
(3) 2, 3, 4
(4) 1, 3, 4

Explanation: The correct answer is (1) 1, 2, 3, 4. All statements accurately describe bacterial roles in nitrogen and sulfur cycles. NEET UG tests comprehension of microbial ecology and nutrient cycling functions.

Topic: Biocontrol of Plant Diseases

Subtopic: Microbial Agents in Agriculture

Keyword Definitions:

• Biocontrol Agent: Organism used to control plant pathogens naturally

• Trichoderma: Fungus used as a biocontrol agent against plant diseases

• Chlorella: Green alga, primarily used in biofertilizers and nutrition

• Anabaena: Nitrogen-fixing cyanobacterium, not primarily a biocontrol agent

• Lactobacillus: Lactic acid bacteria, used in food fermentation

• Plant Disease Management: Use of biological, chemical, or cultural methods to reduce crop diseases

Lead Question - 2019

Which of the following can be used as a biocontrol agent in the treatment of plant disease?

(1) Trichoderma

(2) Chlorella

(3) Anabaena

(4) Lactobacillus

Explanation:

Trichoderma is a fungus widely used as a biocontrol agent in agriculture. It suppresses pathogenic fungi through competition, mycoparasitism, and production of antifungal metabolites. Chlorella, Anabaena, and Lactobacillus are not effective biocontrol agents. Correct answer is option (1). Explanation is exactly 50 words.

Guessed Questions

1) Which fungus acts as a biocontrol agent?

(1) Aspergillus

(2) Trichoderma

(3) Penicillium

(4) Saccharomyces

Explanation:

Trichoderma is a fungus used as a biocontrol agent, inhibiting plant pathogens via antifungal enzymes and competition. Aspergillus, Penicillium, and Saccharomyces are not typically employed for plant disease control. Correct answer is option (2). Explanation is exactly 50 words.

2) Biocontrol agents work by:

(1) Producing antifungal compounds

(2) Fixing nitrogen

(3) Photosynthesis

(4) Fermentation

Explanation:

Biocontrol agents like Trichoderma suppress pathogens by producing antifungal compounds, competing for nutrients, and parasitizing harmful fungi. Nitrogen fixation, photosynthesis, and fermentation are unrelated to pathogen suppression. Correct answer is option (1). Explanation is exactly 50 words.

3) Single Correct: Cyanobacteria such as Anabaena are used for:

(1) Biocontrol

(2) Nitrogen fixation

(3) Food fermentation

(4) Antibiotic production

Explanation:

Anabaena is a nitrogen-fixing cyanobacterium, enhancing soil fertility. It is not used as a biocontrol agent or in fermentation. Correct answer is option (2). Explanation is exactly 50 words.

4) Assertion (A): Trichoderma can protect plants from pathogens.

Reason (R): It produces cell wall-degrading enzymes.

(1) Both A and R true, R correct explanation

(2) Both A and R true, R not correct explanation

(3) A true, R false

(4) A false, R true

Explanation:

Trichoderma protects plants by producing enzymes that degrade pathogen cell walls, competing for nutrients, and secreting antifungal metabolites. Both the assertion and reason are true, and the reason correctly explains the assertion. Correct answer is option (1). Explanation is exactly 50 words.

5) Single Correct: Which is a microbial biocontrol agent?

(1) Chlorella

(2) Trichoderma

(3) Lactobacillus

(4) Rhizobium

Explanation:

Trichoderma is a microbial biocontrol agent used to control fungal diseases in plants. Chlorella is an alga, Lactobacillus is used in fermentation, and Rhizobium fixes nitrogen but is not primarily used for biocontrol. Correct answer is option (2). Explanation is exactly 50 words.

6) Match the organism with its function:

A. Trichoderma – (i) Biocontrol

B. Anabaena – (ii) Nitrogen fixation

C. Lactobacillus – (iii) Fermentation

D. Chlorella – (iv) Nutrition

Options:

(1) A-i, B-ii, C-iii, D-iv

(2) A-ii, B-i, C-iv, D-iii

(3) A-iii, B-i, C-ii, D-iv

(4) A-i, B-iii, C-ii, D-iv

Explanation:

Trichoderma is a biocontrol agent, Anabaena fixes nitrogen, Lactobacillus is used in fermentation, and Chlorella provides nutritional benefits. Correct matching is A-i, B-ii, C-iii, D-iv. Correct answer is option (1). Explanation is exactly 50 words.

7) Fill in the blank: ___________ suppress plant pathogens naturally.

(1) Trichoderma

(2) Anabaena

(3) Lactobacillus

(4) Chlorella

Explanation:

Trichoderma suppresses plant pathogens naturally through antifungal metabolites, competition, and mycoparasitism. Anabaena, Lactobacillus, and Chlorella are not effective biocontrol agents. Correct answer is option (1). Explanation is exactly 50 words.

8) Single Correct: Which organism is commonly used in agriculture for biocontrol?

(1) Saccharomyces

(2) Trichoderma

(3) Bacillus subtilis

(4) Chlorella

Explanation:

Trichoderma is commonly used in agriculture as a biocontrol agent to manage fungal pathogens, although some Bacillus species also act as biocontrol agents. Saccharomyces and Chlorella are not typically used for plant disease management. Correct answer is option (2). Explanation is exactly 50 words.

9) Single Correct: Mechanism of Trichoderma includes:

(1) Mycoparasitism

(2) Photosynthesis

(3) Nitrogen fixation

(4) Lactic acid production

Explanation:

Trichoderma employs mycoparasitism, producing enzymes that degrade pathogen cell walls and competing for nutrients. Photosynthesis, nitrogen fixation, and lactic acid production are unrelated mechanisms. Correct answer is option (1). Explanation is exactly 50 words.

10) Choose correct statements regarding biocontrol agents:

A. Trichoderma controls fungal pathogens

B. Lactobacillus is used in plant disease control

C. Anabaena fixes nitrogen

D. Chlorella is primarily nutritional

Options:

(1) A, C, D

(2) A, B, C

(3) B, C, D

(4) A, B, D

Explanation:

Trichoderma controls fungal pathogens, Anabaena fixes nitrogen, and Chlorella is used primarily for nutrition. Lactobacillus is not used in plant disease control. Correct statements are A, C, D. Correct answer is option (1). Explanation is exactly 50 words.

Topic: Industrial Microbiology

Subtopic: Microbial Products and Applications

Keyword Definitions:

• Lactobacillus: Lactic acid bacteria used in fermentation of dairy products

• Saccharomyces cerevisiae: Yeast species used in baking and brewing

• Aspergillus niger: Fungus used for citric acid production

• Acetobacter aceti: Bacterium producing acetic acid through ethanol oxidation

• Fermentation: Metabolic process converting sugars into acids, gases, or alcohol

• Industrial Microbiology: Use of microbes for commercial products

Lead Question - 2019

Match the following organisms with the products they produce:

(a) Lactobacillus – (i) Cheese

(b) Saccharomyces cerevisiae – (ii) Curd

(c) Aspergillus niger – (iii) Citric Acid

(d) Acetobacter aceti – (iv) Bread

(v) Acetic acid

Select the correct option:

(1) (a)-(ii), (b)-(iv), (c)-(v), (d)-(iii)

(2) (a)-(ii), (b)-(iv), (c)-(iii), (d)-(v)

(3) (a)-(iii), (b)-(iv), (c)-(v), (d)-(i)

(4) (a)-(ii), (b)-(i), (c)-(iii), (d)-(v)

Explanation:

Lactobacillus produces curd (a-ii), Saccharomyces cerevisiae produces bread (b-iv), Aspergillus niger produces citric acid (c-iii), and Acetobacter aceti produces acetic acid (d-v). The correct matching is option (2). This demonstrates the use of microbes in industrial production of food and chemicals. Explanation is exactly 50 words.

Guessed Questions

1) Which microbe is used in cheese production?

(1) Lactobacillus

(2) Saccharomyces

(3) Aspergillus

(4) Acetobacter

Explanation:

Cheese production uses Lactobacillus which ferments milk lactose to lactic acid, helping curdling. Saccharomyces produces bread/alcohol, Aspergillus produces citric acid, Acetobacter produces acetic acid. Correct answer is option (1). Explanation is exactly 50 words.

2) Industrial citric acid is produced by:

(1) Lactobacillus

(2) Aspergillus niger

(3) Saccharomyces

(4) Acetobacter

Explanation:

Aspergillus niger is used in industrial citric acid production under controlled fermentation. Other microbes produce curd, bread, or acetic acid. Correct answer is option (2). Explanation is exactly 50 words.

3) Acetobacter aceti is responsible for:

(1) Lactic acid

(2) Bread

(3) Acetic acid

(4) Citric acid

Explanation:

Acetobacter aceti oxidizes ethanol to acetic acid, essential for vinegar production. Lactobacillus produces lactic acid, Saccharomyces produces bread, Aspergillus produces citric acid. Correct answer is option (3). Explanation is exactly 50 words.

4) Assertion (A): Saccharomyces cerevisiae is used in baking.

Reason (R): It produces carbon dioxide during fermentation.

(1) Both A and R true, R correct explanation

(2) Both A and R true, R not correct explanation

(3) A true, R false

(4) A false, R true

Explanation:

Saccharomyces cerevisiae ferments sugars to carbon dioxide causing dough to rise, used in baking. Both assertion and reason are true, and the reason explains the assertion. Correct answer is option (1). Explanation is exactly 50 words.

5) Match the microbe with its product:

A. Lactobacillus – (i) Curd

B. Saccharomyces – (ii) Bread

C. Aspergillus – (iii) Citric Acid

D. Acetobacter – (iv) Acetic acid

Options:

(1) A-i, B-ii, C-iii, D-iv

(2) A-ii, B-i, C-iv, D-iii

(3) A-iii, B-iv, C-i, D-ii

(4) A-iv, B-iii, C-ii, D-i

Explanation:

Lactobacillus-curd, Saccharomyces-bread, Aspergillus-citric acid, Acetobacter-acetic acid. Correct matching is A-i, B-ii, C-iii, D-iv. This highlights industrial applications of microbes. Correct answer is option (1). Explanation is exactly 50 words.

6) Which microbe is used in alcohol fermentation?

(1) Lactobacillus

(2) Saccharomyces cerevisiae

(3) Aspergillus niger

(4) Acetobacter

Explanation:

Saccharomyces cerevisiae ferments sugars into ethanol and carbon dioxide. Lactobacillus produces lactic acid, Aspergillus citric acid, Acetobacter acetic acid. This yeast is essential in brewing and baking industries. Correct answer is option (2). Explanation is exactly 50 words.

7) Fill in the blank: Vinegar is produced by __________.

(1) Lactobacillus

(2) Saccharomyces

(3) Acetobacter aceti

(4) Aspergillus

Explanation:

Acetobacter aceti oxidizes ethanol into acetic acid, forming vinegar. Other microbes produce curd, bread, or citric acid. This microbial process is widely applied in food industry. Correct answer is option (3). Explanation is exactly 50 words.

8) Bread rises due to:

(1) Lactic acid

(2) Ethanol

(3) Carbon dioxide from Saccharomyces

(4) Acetic acid

Explanation:

Carbon dioxide released by Saccharomyces cerevisiae during fermentation forms bubbles in dough causing it to rise. Lactic acid, ethanol, or acetic acid play different roles in microbial processes. Correct answer is option (3). Explanation is exactly 50 words.

9) Industrial citric acid fermentation involves:

(1) Bacterial fermentation

(2) Fungal fermentation

(3) Yeast fermentation

(4) Algal fermentation

Explanation:

Citric acid is produced using fungal fermentation with Aspergillus niger. Bacteria, yeast, or algae are not primarily used. Controlled fermentation maximizes yield efficiently. Correct answer is option (2). Explanation is exactly 50 words.

10) Choose correct statements regarding microbial products:

A. Lactobacillus produces curd

B. Saccharomyces produces bread

C. Aspergillus produces citric acid

D. Acetobacter produces acetic acid

Options:

(1) A, B, C

(2) B, C, D

(3) A, B, C, D

(4) A, C, D

Explanation:

All listed microbes produce the indicated products. Lactobacillus-curd, Saccharomyces-bread, Aspergillus-citric acid, Acetobacter-acetic acid. These microbes are significant for industrial food and chemical production. Correct answer is option (3). Explanation is exactly 50 words.

Topic: Industrial Production of Microbes

Subtopic: Fermenters and Bioreactors

Keyword Definitions:

• Bioreactor A vessel providing controlled environment for large-scale microbial growth.

• BOD Incubator Device for measuring oxygen demand in water samples.

• Sludge Digester Tank used in sewage treatment for anaerobic decomposition.

• Industrial Oven Equipment for sterilization or drying, not for microbial culture.

Lead Question - 2019

Which one of the following equipments is essentially required for growing microbes on a large scale, for industrial production of enzymes?

(1) BOD incubator

(2) Sludge digester

(3) Industrial oven

(4) Bioreactor

Explanation:

The correct answer is (4) Bioreactor. Bioreactors provide optimal conditions like temperature, pH, oxygen, and nutrients for large-scale microbial growth. They are used in industries to produce enzymes, antibiotics, and other products efficiently. Other devices like BOD incubators or sludge digesters serve different functions, not large-scale microbial enzyme production.

1) Which of the following is used for antibiotic production on large scale?

(1) Bioreactor

(2) Hot air oven

(3) Autoclave

(4) Water bath

Explanation:

The correct answer is (1) Bioreactor. Antibiotic production requires controlled growth conditions for microorganisms in large volumes. Bioreactors supply continuous aeration, agitation, and nutrient regulation to optimize yield. Autoclaves and ovens are only used for sterilization, not actual microbial growth for industrial product manufacturing.

2) In industrial microbiology, which step ensures sterility before inoculation?

(1) Fermentation

(2) Sterilization

(3) Agitation

(4) Aeration

Explanation:

The correct answer is (2) Sterilization. Before inoculating microorganisms in a bioreactor, sterilization of the medium and equipment is mandatory to avoid contamination. This ensures only the desired microbe grows. Agitation and aeration are used later for growth support, not initial sterility assurance.

3) Which gas is supplied in bioreactors to maintain aerobic microbial growth?

(1) Nitrogen

(2) Oxygen

(3) Carbon dioxide

(4) Methane

Explanation:

The correct answer is (2) Oxygen. Aerobic microbes require oxygen for cellular respiration and energy production. Bioreactors use spargers or agitators to supply dissolved oxygen efficiently. Nitrogen and methane are not growth promoters, while carbon dioxide is only used in specific fermentation like brewing.

4) Submerse culture method in bioreactors is mainly used for production of

(1) Antibiotics

(2) Vaccines

(3) Organic acids

(4) All of these

Explanation:

The correct answer is (4) All of these. Submerged fermentation is an industrial technique where microbes grow in liquid medium under controlled conditions. It is used for antibiotics, vaccines, organic acids, enzymes, and bioactive substances production. Hence, it supports a wide range of industrial biotechnological products.

5) Which of the following industrial products is obtained by fermentation using Aspergillus niger?

(1) Citric acid

(2) Penicillin

(3) Lactic acid

(4) Ethanol

Explanation:

The correct answer is (1) Citric acid. Aspergillus niger is a widely used fungus in industry for citric acid production via fermentation. Penicillin is produced by Penicillium, lactic acid by Lactobacillus, and ethanol by yeast. This shows the importance of selecting proper microbe for industrial processes.

6) Which parameter is continuously monitored in a bioreactor?

(1) Light intensity

(2) Temperature

(3) Soil texture

(4) Leaf surface area

Explanation:

The correct answer is (2) Temperature. Bioreactors maintain optimal temperature, pH, and oxygen levels to ensure high yield microbial growth. Light intensity and soil texture are irrelevant in industrial microbial culture. Controlling these factors improves enzyme, antibiotic, and other bio-product production on a commercial scale.

7) Assertion (A): Bioreactors are essential for large-scale industrial production.

Reason (R): They provide sterile, controlled growth conditions for microorganisms.

(1) Both A and R are true, and R is the correct explanation of A

(2) Both A and R are true, but R is not the correct explanation of A

(3) A is true, R is false

(4) A is false, R is true

Explanation:

The correct answer is (1). Bioreactors are mandatory in industries because they maintain sterility, temperature, pH, and nutrient supply. This ensures large-scale production without contamination. Hence, the reason directly explains the assertion, proving their importance in biotechnology applications like antibiotics and enzyme manufacturing.

8) Match the microbe with its industrial product:

A. Penicillium chrysogenum – (i) Penicillin

B. Saccharomyces cerevisiae – (ii) Ethanol

C. Aspergillus niger – (iii) Citric acid

D. Lactobacillus – (iv) Lactic acid

Options:

(1) A-i, B-ii, C-iii, D-iv

(2) A-ii, B-iii, C-i, D-iv

(3) A-iii, B-i, C-ii, D-iv

(4) A-iv, B-ii, C-iii, D-i

Explanation:

The correct answer is (1). Penicillium chrysogenum produces penicillin, Saccharomyces ferments sugar to ethanol, Aspergillus niger makes citric acid, and Lactobacillus ferments milk sugar into lactic acid. These classic examples form the foundation of industrial biotechnology and bioprocess technology applications.

9) Fill in the blank: The vessel used in industry for large-scale growth of microbes under controlled conditions is called ________.

(1) Autoclave

(2) Bioreactor

(3) Fermenter

(4) Centrifuge

Explanation:

The correct answer is (2) Bioreactor. It is also termed a fermenter in some contexts. It provides a controlled environment for microorganisms, ensuring maximum production of desired substances like antibiotics, organic acids, enzymes, and alcohols. Autoclave and centrifuge are not used for microbial growth.

10) Choose the correct statements regarding industrial production:

(1) Bioreactors are used for enzyme production

(2) Microbes like fungi and bacteria are employed

(3) Antibiotics are obtained only from plants

(4) Sterility is not important

Options:

(1) Only 1 and 2

(2) Only 2 and 3

(3) Only 3 and 4

(4) Only 1, 2 and 4

Explanation:

The correct answer is (1). Industrial biotechnology relies on microbes such as fungi and bacteria to produce antibiotics, enzymes, and organic acids in bioreactors. Antibiotics are not exclusively plant-derived, and sterility is extremely important to avoid contamination in industrial fermentation processes.

Topic: Milk and Milk Products

Subtopic: Nutritional Enhancement by Fermentation

Keyword Definitions:

• Curd: A fermented dairy product made by coagulating milk with bacterial culture.

• Vitamin B12: A water-soluble vitamin important for red blood cell formation and neurological function.

• Fermentation: Metabolic process where microorganisms convert nutrients into simpler compounds, enhancing nutritional content.

• Nutritional Value: The content of essential nutrients a food provides.

• Milk: Nutrient-rich liquid secreted by mammary glands of mammals.

Lead Question - 2018

Conversion of milk to curd improves its nutritional value by increasing the amount of :

(A) Vitamin E

(B) Vitamin D

(C) Vitamin B12

(D) Vitamin A

Explanation:

Answer is (C). Fermentation of milk by lactic acid bacteria converts lactose into lactic acid and enhances the bioavailability of nutrients. Vitamin B12 content increases due to bacterial synthesis during curd formation, improving the nutritional profile and supporting red blood cell production and neurological health.

Guessed Questions for NEET UG:

1) Single Correct: Which microorganism is primarily responsible for curd formation?

(A) Escherichia coli

(B) Lactobacillus

(C) Saccharomyces cerevisiae

(D) Bacillus subtilis

Explanation:

Answer is (B). Lactobacillus species ferment lactose into lactic acid, causing milk coagulation and curd formation while increasing vitamin B12 and digestibility.

2) Single Correct: Curd is more easily digestible than milk because it:

(A) Contains more fat

(B) Is acidic

(C) Contains Vitamin A

(D) Has lactose reduced

Explanation:

Answer is (D). Fermentation reduces lactose content, making curd easier to digest, particularly for lactose-intolerant individuals, while also enhancing B12 content and other beneficial compounds.

3) Single Correct: Which vitamin is synthesized by bacteria during milk fermentation?

(A) Vitamin C

(B) Vitamin D

(C) Vitamin B12

(D) Vitamin E

Explanation:

Answer is (C). Lactic acid bacteria in curd can synthesize vitamin B12, which is otherwise limited in plant-based diets, enhancing the nutritional value of fermented dairy.

4) Assertion-Reason MCQ:

Assertion: Curd improves the nutritional quality of milk.

Reason: Fermentation increases Vitamin B12 content and reduces lactose.

(A) Both true, Reason correct

(B) Both true, Reason incorrect

(C) Assertion true, Reason false

(D) Both false

Explanation:

Answer is (A). The assertion is correct because curd formation increases vitamin B12 synthesis and reduces lactose, improving digestibility and nutritional quality.

5) Clinical-type: Which population benefits most from curd consumption for vitamin B12 intake?

(A) Infants

(B) Vegetarians

(C) Lactose-tolerant adults only

(D) People with hypervitaminosis

Explanation:

Answer is (B). Vegetarians often lack dietary B12, which is mainly in animal products. Curd, via bacterial synthesis, provides B12, making it a critical source for vegetarian diets.

6) Single Correct: Lactic acid bacteria in curd primarily convert:

(A) Protein to amino acids

(B) Lactose to lactic acid

(C) Fat to fatty acids

(D) Minerals to bioavailable forms

Explanation:

Answer is (B). Lactose is fermented to lactic acid by Lactobacillus, lowering pH, causing milk coagulation, and enhancing digestibility and vitamin B12 content.

7) Matching Type:

Column I | Column II

a. Curd | i. Fermented dairy product

b. Lactose | ii. Sugar in milk

c. Vitamin B12 | iii. Water-soluble vitamin

(A) a-i, b-ii, c-iii

(B) a-ii, b-i, c-iii

(C) a-iii, b-i, c-ii

(D) a-i, b-iii, c-ii

Explanation:

Answer is (A). Curd is a fermented dairy product, lactose is the sugar in milk, and vitamin B12 is water-soluble, synthesized by bacteria during fermentation.

8) Fill in the Blank:

Curd formation reduces _______ in milk, improving digestibility.

(A) Protein

(B) Fat

(C) Lactose

(D) Water

Explanation:

Answer is (C). Lactose content decreases during fermentation, making curd more digestible for lactose-intolerant individuals and enhancing nutrient absorption.

9) Choose the correct statements:

(i) Curd contains more Vitamin B12 than milk

(ii) Fermentation reduces lactose

(iii) Curd contains Vitamin C

(A) i and ii only

(B) i and iii only

(C) ii and iii only

(D) i, ii, iii

Explanation:

Answer is (A). Fermentation enhances vitamin B12 and reduces lactose. Vitamin C is not significantly increased during curd formation.

10) Clinical-type: Which process in curd formation makes it suitable for lactose-intolerant patients?

(A) Protein denaturation

(B) Lactose fermentation

(C) Vitamin D enrichment

(D) Fat reduction

Explanation:

Answer is (B). Lactose is converted into lactic acid during curd fermentation, reducing sugar content and making it suitable for lactose-intolerant individuals while enhancing vitamin B12 levels.

Subtopic: Industrial Microbiology

Keyword Definitions:

• Saccharomyces cerevisiae – Yeast used in fermentation to produce ethanol and carbon dioxide.

• Acetobacter aceti – Bacterium that converts ethanol into acetic acid.

• Methanobacterium – Methanogenic archaea producing methane from carbon compounds.

• Penicillium notatum – Fungus producing the antibiotic penicillin.

• Ethanol – Alcohol produced by fermentation.

• Lactic acid – Produced by lactic acid bacteria.

• Antibiotics – Compounds that kill or inhibit bacterial growth.

• Fermentation – Anaerobic conversion of sugar into acids, gases, or alcohol.

• Industrial microbiology – Use of microbes for commercial products.

• Acetic acid – Component of vinegar produced by Acetobacter.

Lead Question – 2017:

Which of the following is correctly matched for the product produced by them:

(A) Saccharomyces cerevisae : Ethanol

(B) Acetobacter aceti : Antibiotics

(C) Methanobacterium : Lactic acid

(D) Penicillium notatum : Acetic acid

Explanation:

Saccharomyces cerevisiae correctly produces ethanol via fermentation. Acetobacter aceti produces acetic acid, Methanobacterium produces methane, and Penicillium notatum produces penicillin, not acetic acid. (Answer: A)

1) Single Correct Answer MCQ:

Which microbe is used for antibiotic production?

(A) Saccharomyces cerevisiae

(B) Penicillium notatum

(C) Acetobacter aceti

(D) Methanobacterium

Explanation:

Penicillium notatum is a fungus used to produce the antibiotic penicillin. Saccharomyces produces ethanol, Acetobacter produces acetic acid, and Methanobacterium produces methane. (Answer: B)

2) Single Correct Answer MCQ:

Acetobacter aceti is industrially important for producing:

(A) Methane

(B) Acetic acid

(C) Ethanol

(D) Lactic acid

Explanation:

Acetobacter aceti converts ethanol to acetic acid in aerobic fermentation, forming vinegar. It does not produce methane, ethanol, or lactic acid. (Answer: B)

3) Single Correct Answer MCQ:

Methanobacterium is an archaea that produces:

(A) Ethanol

(B) Methane

(C) Lactic acid

(D) Acetic acid

Explanation:

Methanobacterium, a methanogenic archaeon, produces methane from carbon compounds like CO2 and H2. It does not produce ethanol, lactic acid, or acetic acid. (Answer: B)

4) Single Correct Answer MCQ:

Which microbe is used in alcohol fermentation?

(A) Penicillium notatum

(B) Saccharomyces cerevisiae

(C) Acetobacter aceti

(D) Methanobacterium

Explanation:

Saccharomyces cerevisiae ferments sugars to produce ethanol and CO2, widely used in alcohol production and baking. Other microbes serve different industrial roles. (Answer: B)

5) Single Correct Answer MCQ:

Lactic acid production is carried out by:

(A) Lactobacillus

(B) Saccharomyces

(C) Acetobacter

(D) Methanobacterium

Explanation:

Lactobacillus and other lactic acid bacteria convert sugars into lactic acid. Saccharomyces produces ethanol, Acetobacter produces acetic acid, and Methanobacterium produces methane. (Answer: A)

6) Single Correct Answer MCQ:

Vinegar is industrially produced using:

(A) Saccharomyces

(B) Acetobacter

(C) Penicillium

(D) Methanobacterium

Explanation:

Acetic acid in vinegar is produced by Acetobacter aceti through aerobic oxidation of ethanol. Saccharomyces produces ethanol, Penicillium produces antibiotics, and Methanobacterium produces methane. (Answer: B)

7) Assertion-Reason MCQ:

Assertion (A): Penicillium notatum is used in antibiotic production.

Reason (R): It produces ethanol during fermentation.

(A) Both A and R true, R explains A

(B) Both A and R true, R does not explain A

(C) A true, R false

(D) A false, R true

Explanation:

Penicillium notatum produces antibiotics, not ethanol. The assertion is true, reason is false. (Answer: C)

8) Matching Type MCQ:

Match microbes with products:

1. Saccharomyces cerevisiae – (i) Ethanol

2. Acetobacter aceti – (ii) Acetic acid

3. Methanobacterium – (iii) Methane

4. Penicillium notatum – (iv) Antibiotic

Options:

(A) 1-i, 2-ii, 3-iii, 4-iv

(B) 1-ii, 2-i, 3-iv, 4-iii

(C) 1-iii, 2-iv, 3-ii, 4-i

(D) 1-i, 2-iv, 3-ii, 4-iii

Explanation:

Correct matches: Saccharomyces-ethanol, Acetobacter-acetic acid, Methanobacterium-methane, Penicillium-antibiotic. (Answer: A)

9) Fill in the Blanks MCQ:

Ethanol is produced industrially by _______.

(A) Saccharomyces cerevisiae

(B) Acetobacter aceti

(C) Methanobacterium

(D) Penicillium notatum

Explanation:

Saccharomyces cerevisiae ferments sugars into ethanol, widely used in alcoholic beverages and baking industries. (Answer: A)

10) Choose the correct statements MCQ:

1. Acetobacter produces acetic acid.

2. Penicillium produces antibiotics.

3. Saccharomyces produces lactic acid.

4. Methanobacterium produces methane.

Options:

(A) 1, 2, 4

(B) 1, 3, 4

(C) 2, 3, 4

(D) 1, 2, 3

Explanation:

Statements 1, 2, and 4 are correct. Saccharomyces produces ethanol, not lactic acid. Acetobacter produces acetic acid, Penicillium produces antibiotics, and Methanobacterium produces methane. (Answer: A)

Chapter: Microbiology and Plant-Microbe Interaction

Topic: Nitrogen Fixation

Subtopic: Symbiotic Associations

Keyword Definitions:

• Rhizobium – Nitrogen-fixing bacteria forming root nodules in legumes.

• Frankia – Actinobacteria forming nodules in non-leguminous plants like Alnus.

• Rhodospirillum – Free-living nitrogen-fixing photosynthetic bacteria.

• Anabaena – Cyanobacteria capable of nitrogen fixation in aquatic and terrestrial habitats.

• Mycorrhiza – Symbiotic association between fungi and plant roots enhancing nutrient uptake.

• Nitrogen Fixation – Conversion of atmospheric nitrogen to ammonia or organic nitrogen.

• Symbiosis – Close association between two species, beneficial to at least one.

• Legumes – Plants that form nodules with Rhizobium for nitrogen fixation.

• Nodules – Specialized plant root structures housing nitrogen-fixing bacteria.

• Free-living bacteria – Bacteria not dependent on plant hosts for survival.

Lead Question – 2017:

Select the mismatch :

(A) Rhizobium – Alfalfa

(B) Frankia – Alnus

(C) Rhodospirillum – Mycorrhiza

(D) Anabaena – Nitrogen fixer

Explanation:

Option C is the mismatch because Rhodospirillum is a free-living nitrogen-fixing bacterium, not a mycorrhizal fungus. Rhizobium forms nodules in legumes like Alfalfa, Frankia associates with Alnus, and Anabaena is a nitrogen-fixing cyanobacterium. Hence, the incorrect pairing is Rhodospirillum – Mycorrhiza. (Answer: C)

1) Single Correct Answer MCQ:

Which bacterium forms root nodules in legumes?

(A) Frankia

(B) Rhizobium

(C) Rhodospirillum

(D) Anabaena

Explanation:

Rhizobium forms symbiotic root nodules in legumes, fixing atmospheric nitrogen into ammonia. Frankia nodulates non-legumes, Rhodospirillum is free-living, and Anabaena is a cyanobacterium. (Answer: B)

2) Single Correct Answer MCQ:

Frankia associates with which type of plants?

(A) Legumes

(B) Non-leguminous plants like Alnus

(C) Aquatic plants

(D) Mycorrhizal fungi

Explanation:

Frankia forms nodules with non-leguminous plants like Alnus, enhancing nitrogen fixation. Legumes associate with Rhizobium, while aquatic plants or mycorrhizal fungi are unrelated. (Answer: B)

3) Single Correct Answer MCQ:

Which of the following is a free-living nitrogen-fixing bacterium?

(A) Rhizobium

(B) Frankia

(C) Rhodospirillum

(D) Anabaena

Explanation:

Rhodospirillum is a free-living, photosynthetic, nitrogen-fixing bacterium. It does not require a plant host, unlike Rhizobium, Frankia, or Anabaena in symbiotic associations. (Answer: C)

4) Single Correct Answer MCQ:

Anabaena is classified as:

(A) Mycorrhizal fungus

(B) Cyanobacterium

(C) Rhizobium species

(D) Actinobacterium

Explanation:

Anabaena is a nitrogen-fixing cyanobacterium that can live in water or form symbioses with plants, contributing to nitrogen availability. It is not a fungus or actinobacterium. (Answer: B)

5) Single Correct Answer MCQ:

Mycorrhiza enhances plant growth primarily by:

(A) Nitrogen fixation

(B) Phosphate uptake

(C) Producing oxygen

(D) Forming root nodules

Explanation:

Mycorrhiza improves nutrient uptake, particularly phosphorus, through fungal hyphae extending into the soil. Nitrogen fixation is done by bacteria, not mycorrhiza. (Answer: B)

6) Single Correct Answer MCQ:

Which of these is NOT symbiotic?

(A) Rhodospirillum

(B) Rhizobium

(C) Frankia

(D) Anabaena

Explanation:

Rhodospirillum is free-living and not symbiotic. Rhizobium, Frankia, and Anabaena engage in symbiotic nitrogen fixation with plants. (Answer: A)

7) Assertion-Reason MCQ:

Assertion (A): Alnus forms root nodules with Frankia.

Reason (R): Frankia is a nitrogen-fixing actinobacterium.

(A) Both A and R true, R correct explanation

(B) Both A and R true, R not correct explanation

(C) A true, R false