Microbes in Human Welfare

1. The vitamin whose content increases following the conversion of milk into curd by lactic acid bacteria is:

a. vitamin C

b. vitamin D

c. vitamin B12

d. vitamin E.

Key Answer: c. vitamin B12

Explanation: Lactic acid bacteria increase vitamin B12 content during curd formation. Fermentation improves nutritional value of milk.

2. Wastewater treatment generates a large quantity of sludge, which can be treated by:

a. anaerobic digesters

b. floc

c. chemicals

d. oxidation pond.

Key Answer: a. anaerobic digesters

Explanation: Sludge is decomposed anaerobically by microbes in digesters. This process also produces biogas.

3. Methanogenic bacteria are not found in:

a. rumen of cattle

b. gobar gas plant

c. bottom of water-logged paddy fields

d. activated sludge.

Key Answer: d. activated sludge

Explanation: Activated sludge mainly contains aerobic microbes. Methanogens grow only under anaerobic conditions.

4. Match the following list of bacteria and their commercially important products:

Bacterium | Product

A. Aspergillus niger | i. Lactic acid

B. Acetobacter aceti | ii. Butyric acid

C. Clostridium butylicum | iii. Acetic acid

D. Lactobacillus | iv. Citric acid

Choose the correct match:

a. A-ii, B-iii, C-iv, D-i

b. A-ii, B-iv, C-iii, D-i

c. A-iv, B-iii, C-ii, D-i

d. A-iv, B-i, C-iii, D-ii

Key Answer: c. A-iv, B-iii, C-ii, D-i

Explanation: Aspergillus niger produces citric acid and Lactobacillus produces lactic acid. Acetobacter aceti forms acetic acid while Clostridium butylicum forms butyric acid.

5. Match the following list of bioactive substances and their roles:

Bioactive Substance | Role

A. Statin | i. Removal of oil stains

B. Cyclosporin A | ii. Removal of clots from blood vessels

C. Streptokinase | iii. Lowering of blood cholesterol

D. Lipase | iv. Immuno-suppressive agent

Choose the correct match:

a. A-ii, B-iii, C-i, D-iv

b. A-iv, B-ii, C-i, D-iii

c. A-iv, B-i, C-ii, D-iii

d. A-iii, B-iv, C-ii, D-i

Key Answer: d. A-iii, B-iv, C-ii, D-i

Explanation: Statins reduce cholesterol and Streptokinase dissolves blood clots. Lipases remove oil stains while Cyclosporin A suppresses immunity.

6. The primary treatment of waste water involves the removal of:

a. dissolved impurities

b. stable particles

c. toxic substances

d. harmful bacteria.

Key Answer: b. stable particles

Explanation: Primary treatment removes floating and suspended solids. Physical processes like sedimentation are used.

7. BOD of waste water is estimated by measuring the amount of:

a. total organic matter

b. biodegradable organic matter

c. oxygen evolution

d. oxygen consumption.

Key Answer: d. oxygen consumption

Explanation: BOD measures oxygen used by microbes to decompose organic matter. Higher BOD indicates more pollution.

8. Which one of the following alcoholic drinks is produced without distillation?

a. Wine

b. Whisky

c. Rum

d. Brandy

Key Answer: a. Wine

Explanation: Wine is produced only by fermentation. Whisky, rum and brandy require distillation.

9. The technology of biogas production from cow dung was developed in India largely due to the efforts of:

a. Gas Authority of India

b. Oil and Natural Gas Commission

c. Indian Agricultural Research Institute and Khadi & Village Industries Commission

d. Indian Oil Corporation.

Key Answer: c. Indian Agricultural Research Institute and Khadi & Village Industries Commission

Explanation: These organizations popularized biogas technology in rural India. They developed efficient gobar gas plants.

10. The free-living fungus Trichoderma can be used for:

a. killing insects

b. biological control of plant diseases

c. controlling butterfly caterpillars

d. producing antibiotics

Key Answer: b. biological control of plant diseases

Explanation: Trichoderma acts as a biocontrol agent against plant pathogens. It protects crops naturally.

11. What would happen if oxygen availability to activated sludge flocs is reduced?

a. It will slow down the rate of degradation of organic matter

b. The center of flocs will become anoxic, which would cause death of bacteria and eventually breakage of flocs.

c. Flocs would increase in size as anaerobic bacteria would grow around flocs.

d. Protozoa would grow in large numbers.

Key Answer: a. It will slow down the rate of degradation of organic matter

Explanation: Aerobic microbes require oxygen for decomposition. Reduced oxygen decreases treatment efficiency.

12. Mycorrhiza does not help the host plant in:

a. Enhancing its phosphorus uptake capacity

b. Increasing its tolerance to drought

c. Enhancing its resistance to root pathogens

d. Increasing its resistance to insects.

Key Answer: d. Increasing its resistance to insects.

Explanation: Mycorrhiza improves nutrient uptake and disease resistance. It does not directly protect against insects.

13. Which one of the following is not a nitrogen-fixing organism?

a. Anabaena

b. Nostoc

c. Azotobacter

d. Pseudomonas

Key Answer: d. Pseudomonas

Explanation: Anabaena, Nostoc and Azotobacter fix atmospheric nitrogen. Pseudomonas generally does not.

14. Big holes in Swiss cheese are made by a:

a. a machine

b. a bacterium that produces methane gas

c. a bacterium producing a large amount of carbon dioxide

d. a fungus that releases a lot of gases during its metabolic activities.

Key Answer: c. a bacterium producing a large amount of carbon dioxide

Explanation: Propionibacterium releases carbon dioxide during fermentation. Gas bubbles create holes in Swiss cheese.

15. The residue left after methane production from cattle dung is:

a. burnt

b. burried in land fills

c. used as manure

d. used in civil construction.

Key Answer: c. used as manure

Explanation: The digested slurry is nutrient-rich organic manure. It improves soil fertility.

16. Methanogens do not produce:

a. oxygen

b. methane

c. hydrogen sulfide

d. carbon dioxide.

Key Answer: a. oxygen

Explanation: Methanogens are anaerobic microbes and cannot release oxygen. They mainly produce methane and gases like CO₂.

17. Activated sludge should have the ability to settle quickly so that it can:

a. be rapidly pumped back from sedimentation tank to aeration tank

b. absorb pathogenic bacteria present in waste water while sinking to the bottom of the settling tank

c. be discarded and anaerobically digested

d. absorb colloidal organic matter.

Key Answer: a. be rapidly pumped back from sedimentation tank to aeration tank

Explanation: Fast settling allows recycling of active microbes into aeration tanks. This maintains efficient sewage treatment.

18. Match the items in Column ‘A’ and Column ‘B’ and choose correct answer.

Column I | Column II

A. Lady bird | i. Methano bacterium

B. Mycorrhiza | ii. Trichoderma

C. Biological control | iii. Aphids

D. Biogas | iv. Glomus

The correct answer is:

a. A-ii, B-iv, C-iii, D-i

b. A-iii, B-iv, C-ii, D-i

c. A-iv, B-i, C-ii, D-iii

d. A-iii, B-ii, C-i, D-iv

Key Answer: b. A-iii, B-iv, C-ii, D-i

Explanation: Lady bird controls aphids and Glomus forms mycorrhiza. Trichoderma is used in biological control and methanobacteria produce biogas.