Microbes in Human Welfare NEET PYQReal NEET & AIPMT 2005–2021 questions, year-tagged, with solutions
By the RankUp team, founded by Dr. Deepak Sahu (MBBS Gold Medalist, NEET PG AIR 1731) · Updated
Every Microbes in Human Welfare question from the NEET & AIPMT papers on this site (2005–2021), newest first. Each is tagged with its paper. Tap an option to check your answer and read the explanation.
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Microbes in Human Welfare previous year questions
49 questions. Tap an option to check your answer.
Q1NEET 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.
Not quite — the answer is A.
Aspergillus niger produces citric acid, Acetobacter aceti acetic acid, Clostridium butylicum butyric acid, and Lactobacillus lactic acid. Hence (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii).
Q2NEET 2020 · Q23
Which of the following is put into Anaerobic sludge digester for further sewage treatment?
Not quite — the answer is D.
After secondary treatment the floc settles as activated sludge; a small part is sent back to the aeration tank as inoculum and the major part goes into anaerobic sludge digesters. Primary sludge and floating debris are removed earlier, and the primary effluent goes to the aeration tank, not to the digester.
Q3NEET 2020 · Q48
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
Not quite — the answer is B.
Clostridium butylicum produces butyric acid, Trichoderma polysporum gives cyclosporin A, Monascus purpureus gives statins that lower blood cholesterol, and Aspergillus niger produces citric acid. Hence butyric acid, cyclosporin A, cholesterol-lowering agent, citric acid is correct.
Q4NEET 2019 · Q96
Which of the following is a commercial blood cholesterol lowering agent ?
Not quite — the answer is B.
Statins, produced by the yeast Monascus purpureus, competitively inhibit the enzyme of cholesterol synthesis and lower blood cholesterol. Cyclosporin A is an immunosuppressant and streptokinase is a clot buster.
Q5NEET 2019 · Q123
Select the correct group of biocontrol agents.
Not quite — the answer is B.
Trichoderma (fungal biocontrol of plant pathogens), baculoviruses (insect pathogens) and Bacillus thuringiensis (Bt toxin against caterpillars) are all biocontrol agents. Tobacco mosaic virus and aphids are plant pests, while Rhizobium, Nostoc and Azospirillum are biofertilisers.
Q6NEET 2019 · Q125
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.
Not quite — the answer is B.
Lactobacillus converts milk to curd, Saccharomyces cerevisiae (baker's yeast) leavens bread, Aspergillus niger produces citric acid and Acetobacter aceti produces acetic acid. Swapping citric and acetic acid between the fungus and the bacterium is the common error.
Q7NEET 2019 · Q169
Which of the following can be used as a biocontrol agent in the treatment of plant disease ?
Not quite — the answer is A.
Trichoderma species are free-living fungi in root ecosystems that act against several plant pathogens. Anabaena is a nitrogen-fixing biofertiliser and Chlorella is a source of single cell protein.
Q8NEET 2018 · Q178
Conversion of milk to curd improves its nutritional value by increasing the amount of
Not quite — the answer is A.
Lactic acid bacteria such as Lactobacillus that turn milk into curd also increase its vitamin B₁₂ content, which NCERT notes as the nutritional improvement. They do not synthesise the fat-soluble vitamins A, D or E.
Q9NEET 2017 · Q46
Which of the following in sewage treatment removes suspended solids?
Not quite — the answer is C.
Primary treatment is the physical stage: floating debris is removed by sequential filtration and grit and suspended solids settle out by sedimentation as primary sludge. Secondary treatment is biological and removes dissolved organic matter (BOD) through microbes, not suspended solids.
Q10NEET 2017 · Q123
Select the mismatch:
Not quite — the answer is B.
Rhodospirillum is a free-living, anaerobic photosynthetic nitrogen-fixing bacterium, while mycorrhiza is an association of a fungus with plant roots, so that pairing is the mismatch. Frankia forms root nodules on Alnus, Anabaena is a nitrogen-fixing cyanobacterium and Rhizobium nodulates legumes such as alfalfa.
Q11NEET 2016 Phase 1 · Q169
Which of the following is wrongly matched in the given table?
Not quite — the answer is D.
Clostridium butylicum is used to produce butyric acid, not lipase; lipases for removing oily stains in detergents come from other microbes. Cyclosporin A from Trichoderma, statins from Monascus and streptokinase from Streptococcus are correctly matched.
Q12NEET 2016 Phase 1 · Q177
The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the:
Not quite — the answer is C.
Methanogens such as Methanobacterium are archaebacteria in the rumen and in cattle dung that produce methane, the main component of biogas. Halophiles and thermoacidophiles are archaebacteria of salty and hot acidic habitats.
Q13AIPMT 2015
The guts of cow and buffalo possess:
Not quite — the answer is D.
The rumen of cattle and buffalo contains methanogens such as Methanobacterium, which help break down cellulose and release methane. Cyanobacteria, Chlorella and Fucus are photosynthetic and do not live in the gut.
Q14AIPMT 2014
What gases are produced in anaerobic sludge digesters?
Not quite — the answer is A.
Anaerobic bacteria digesting sludge produce biogas, a mixture of methane, hydrogen sulphide and carbon dioxide. Oxygen is not produced in this anaerobic process, and listing only methane and CO₂ or only H₂S and CO₂ leaves out a component.
Q15NEET 2013
A good producer of citric acid is
Not quite — the answer is A.
The fungus Aspergillus niger is the industrial producer of citric acid. Saccharomyces is used for ethanol and baking, and Clostridium for butyric acid.
Q16NEET 2013
During sewage treatment, biogases are produced which include
Not quite — the answer is A.
In the anaerobic sludge digesters of a sewage treatment plant, bacteria produce biogas consisting of methane, hydrogen sulphide and carbon dioxide. Oxygen is not produced under anaerobic conditions.
Q17AIPMT 2012 Mains
In gobar gas, the maximum amount is that of
Not quite — the answer is B.
Biogas (gobar gas) produced by methanogens in cattle dung is mostly methane, about 50–70%. Carbon dioxide is the second main component but present in a smaller amount.
Q18AIPMT 2012 Prelims
A patient brought to a hospital with myocardial infarction is normally immediately given
Not quite — the answer is C.
Streptokinase, produced by Streptococcus and modified by genetic engineering, is a clot buster that dissolves blood clots in the coronary arteries of myocardial infarction patients. Statins lower blood cholesterol and cyclosporin A is an immunosuppressant used in organ transplants.
Q19AIPMT 2012 Prelims
Measuring Biochemical Oxygen Demand (BOD) is a method used for
Not quite — the answer is B.
BOD is the amount of oxygen consumed if all the organic matter in one litre of water were oxidised by bacteria, so it measures the organic matter in sewage. It has nothing to do with RBC oxygen carrying, engines, or curd making, which is in any case done by Lactobacillus and not yeast.
Q20AIPMT 2012 Prelims
Yeast is used in the production of
Not quite — the answer is D.
Saccharomyces cerevisiae (baker's/brewer's yeast) is used to make bread by fermenting dough and to brew beer. Cheese and butter depend on bacteria, citric acid comes from Aspergillus, and lactic acid from Lactobacillus.
Q21AIPMT 2012 Prelims
Which one of the following is an example of carrying out biological control of pests/diseases using microbes ?
Not quite — the answer is B.
Trichoderma is a free-living fungus used as a biocontrol agent against several plant pathogens, so it is microbial biocontrol. A ladybird beetle is an insect, not a microbe; nucleopolyhedrovirus is used against insect pests, not white rust; and Bt-cotton is a transgenic crop, not biocontrol.
Q22AIPMT 2012 Prelims
A nitrogen-fixing microbe associated with Azolla in rice fields is
Not quite — the answer is C.
The cyanobacterium Anabaena azollae lives in the leaf cavities of the water fern Azolla and fixes nitrogen, so Azolla is used as a biofertiliser in rice fields. Frankia forms nodules on non-legumes like Alnus, and Spirulina is grown as single-cell protein.
Q23AIPMT 2012 Prelims
Which one of the following microbes forms symbiotic association with plants and helps them in their nutrition ?
Not quite — the answer is D.
Glomus is a fungus that forms mycorrhiza with plant roots and helps absorb phosphorus from the soil. Azotobacter is a free-living nitrogen fixer and Trichoderma is a free-living biocontrol fungus, not a symbiont.
Q24AIPMT 2012 Prelims
Monascus purpureus is a yeast used commercially in the production of
Not quite — the answer is A.
The yeast Monascus purpureus produces statins, which lower blood cholesterol by competitively inhibiting the enzyme that synthesises cholesterol. Streptokinase comes from Streptococcus, citric acid from Aspergillus niger and ethanol from Saccharomyces.
Q25AIPMT 2011 Mains
Read the following statement having two blanks (A and B): "A drug used for ___(A)___ patients is obtained from a species of the organism ___(B)___." The one correct option for the two blanks is
Not quite — the answer is D.
Cyclosporin A, an immunosuppressant given to organ-transplant patients, is obtained from the fungus Trichoderma polysporum. Monascus yields statins (cholesterol-lowering), and Penicillium yields penicillin, an antibiotic rather than a heart drug.
Q26AIPMT 2011 Mains
Which one of the following is a wrong matching of a microbe and its industrial product, while the remaining three are correct?
Not quite — the answer is A.
Clostridium butylicum produces butyric acid; lactic acid comes from bacteria such as Lactobacillus, so this pair is wrong. Aspergillus niger produces citric acid, Acetobacter aceti acetic acid, and the yeast Monascus purpureus statins.
Q27AIPMT 2011 Prelims
Secondary sewage treatment is mainly a
Not quite — the answer is A.
Secondary treatment of sewage is a biological process: the primary effluent is aerated so that aerobic microbes form flocs and consume the organic matter, reducing the BOD. Primary treatment, by contrast, is a physical removal of debris by filtration and sedimentation.
Q28AIPMT 2011 Prelims
Which one of the following is not a biofertilizer?
Not quite — the answer is B.
Agrobacterium tumefaciens is a plant pathogen that causes crown gall and is used as a vector in genetic engineering, not as a biofertiliser. Rhizobium and Nostoc fix nitrogen, and mycorrhiza helps phosphorus uptake.
Q29AIPMT 2011 Prelims
Which one of the following helps in absorption of phosphorus from soil by plants?
Not quite — the answer is B.
Fungi of the genus Glomus form mycorrhiza with plant roots and help absorb phosphorus from the soil. Anabaena, Rhizobium and Frankia are nitrogen fixers.
Q30AIPMT 2011 Prelims
Which of the following is mainly produced by the activity of anaerobic bacteria on sewage?
Not quite — the answer is A.
In sludge digesters, anaerobic bacteria (including methanogens) break down sewage and give off a gas mixture rich in methane, also called marsh gas or biogas. Laughing gas is nitrous oxide, and mustard gas is a chemical weapon.
Q31AIPMT 2011 Prelims
Ethanol is commercially produced through a particular species of
Not quite — the answer is B.
Ethanol is produced commercially by fermentation with the yeast Saccharomyces cerevisiae. Aspergillus is used for citric acid, Clostridium for butyric acid and Trichoderma for cyclosporin A.
Q32AIPMT 2011 Prelims
The most common substrate used in distilleries for the production of ethanol is
Not quite — the answer is A.
Molasses, the sugar-rich by-product of sugarcane processing, is the most common substrate fermented by yeast in distilleries. Corn meal can be used but needs starch hydrolysis first, and soya meal and gram are protein-rich.
Q33AIPMT 2011 Prelims
An organism used as biofertilizer for raising soyabean crop is
Not quite — the answer is D.
Soyabean is a legume, and Rhizobium forms root nodules on legumes and fixes atmospheric nitrogen symbiotically. Azotobacter and Azospirillum are free-living or associative fixers, and Nostoc is a cyanobacterium used for paddy fields.
Q34AIPMT 2010 Mains · Q28
An example of endomycorrhiza is
Not quite — the answer is B.
Glomus is a fungus that forms vesicular-arbuscular mycorrhiza, growing inside root cortical cells (endomycorrhiza) and helping the plant absorb phosphorus. Nostoc is a cyanobacterium, Rhizobium is a nitrogen-fixing bacterium, and Agaricus is a mushroom, none of which form endomycorrhiza.
Q35AIPMT 2010 Prelims · Q175
Select the correct statement from the following
Not quite — the answer is A.
Activated sludge is the settled mass of aerobic bacterial flocs from secondary treatment, and part of it is pumped back as inoculum. Biogas is made by anaerobic methanogens such as Methanobacterium, and it is a mixture of mainly methane with CO₂ and H₂, not pure methane.
Q36AIPMT 2010 Prelims · Q182
Which one of the following is not used in organic farming?
Not quite — the answer is A.
Glomus (a mycorrhizal fungus) and Oscillatoria (a cyanobacterium) are biofertilisers, and earthworms make vermicompost, so all three help organic farming. Snails have no such role and are usually crop pests.
Q37AIPMT 2010 Prelims · Q183
A common biocontrol agent for the control of plant diseases is
Not quite — the answer is A.
The free-living fungus Trichoderma lives in the root ecosystem and controls several plant pathogens, so it is used against plant diseases. Baculoviruses and Bacillus thuringiensis are biocontrol agents against insect pests rather than diseases, and Glomus is a biofertiliser.
Q38AIPMT 2009 Prelims · Q74
Biochemical Oxygen Demand (BOD) in a river water:
Not quite — the answer is C.
BOD is the amount of oxygen consumed when microbes oxidise the organic matter in a litre of water; sewage adds a lot of organic matter, so BOD rises. BOD is about oxygen use by microbes in general, not a count of Salmonella.
Q39AIPMT 2009 Prelims · Q114
Which one of the following pairs is wrongly matched?
Not quite — the answer is A.
Alcohol is produced by yeast fermentation using zymase enzymes; nitrogenase is the nitrogen-fixing enzyme and has no role in alcohol production. Pectinases clarify fruit juices, lipases are used in detergents and amylases are used for desizing textiles.
Q40AIPMT 2009 Prelims · Q115
Which of the following is not used as a biopesticide?
Not quite — the answer is C.
Xanthomonas campestris is a plant pathogen (black rot of crucifers) and is used commercially for xanthan gum, not as a biopesticide. Trichoderma, nucleopolyhedroviruses and Bacillus thuringiensis are all NCERT examples of biocontrol agents.
Q41AIPMT 2009 Prelims · Q141
Which of the following is a symbiotic nitrogen fixer?
Not quite — the answer is B.
Frankia is an actinomycete that fixes nitrogen in root nodules of non-leguminous plants such as Alnus, a symbiotic association. Azotobacter is free-living, Azolla is a fern that hosts the nitrogen-fixer Anabaena, and Glomus is a mycorrhizal fungus that helps phosphorus uptake.
Q42AIPMT 2009 Prelims · Q145
The bacterium Bacillus thuringiensis is widely used in contemporary biology as:
Not quite — the answer is A.
Bacillus thuringiensis spores and its Bt toxin genes are used to kill insect larvae such as caterpillars, making it a biological insecticide. Dairy products are made with lactic acid bacteria, not Bt.
Q43AIPMT 2008 Prelims · Q184
Trichoderma harzianum has proved a useful microorganism for
Not quite — the answer is A.
Trichoderma species are free-living fungi in the root ecosystem, and NCERT lists them as biocontrol agents against several plant pathogens. Gene transfer in plants is done with Agrobacterium, not Trichoderma.
Q44AIPMT 2008 Prelims · Q192
Modern detergents contain enzyme preparations of
Not quite — the answer is C.
Laundry detergents work in alkaline wash water, so the proteases and lipases added to them come from alkaliphilic microbes (for example alkaliphilic Bacillus species) whose enzymes stay active at high pH. Enzymes from acidophiles would lose activity in an alkaline detergent solution.
Q45AIPMT 2008 Prelims · Q194
Which one of the following proved effective for biological control of nematodal disease in plants?
Not quite — the answer is A.
Paecilomyces lilacinus is a nematophagous fungus that parasitises the eggs of root-knot and cyst nematodes and is sold as a bionematicide. Pisolithus tinctorius is an ectomycorrhizal fungus, and Gliocladium virens and Pseudomonas cepacia are mainly used against fungal pathogens.
Q46AIPMT 2007 Prelims · Q112
Probiotics are
Not quite — the answer is C.
Probiotics are live beneficial microbes, such as Lactobacillus, taken as food supplements to improve the balance of gut microflora. They are living organisms, not antibiotics, which are chemicals that kill or inhibit microbes.
Q47AIPMT 2007 Prelims · Q137
Which one of the following statements is correct?
Not quite — the answer is D.
Fertiliser run-off adds nitrates and phosphates to lakes and ponds, causing algal blooms and eutrophication. Azotobacter is free-living and does not form root nodules, and Anabaena and Nostoc fix nitrogen rather than mobilising phosphate (that is done by mycorrhizal fungi such as Glomus).
Q48AIPMT 2007 Prelims · Q142
Which one of the following pairs is wrongly matched?
Not quite — the answer is C.
Vinegar (acetic acid) is produced by Acetobacter aceti, not by coliforms; coliforms are gut bacteria used as indicators of faecal contamination. Yeast makes ethanol, Streptomyces makes antibiotics and methanogens produce biogas, so those pairs are correct.
Q49AIPMT 2005 Prelims · Q108
For retting of jute the fermenting microbe used is :
Not quite — the answer is D.
During retting, jute stems are soaked in water and anaerobic butyric acid bacteria (such as Clostridium) break down the pectin that holds the fibres together, which frees the fibres. Helicobacter pylori causes stomach ulcers and lactic streptococci sour milk; neither one rets fibres.
How often Microbes in Human Welfare came up
Questions from this chapter in each paper on this site.
- NEET 2021: 1
- NEET 2020: 2
- NEET 2019: 4
- NEET 2018: 1
- NEET 2017: 2
- NEET 2016 Phase 1: 2
- AIPMT 2015: 1
- AIPMT 2014: 1
- NEET 2013: 2
- AIPMT 2012 Mains: 1
- AIPMT 2012 Prelims: 7
- AIPMT 2011 Mains: 2
- AIPMT 2011 Prelims: 7
- AIPMT 2010 Mains: 1
- AIPMT 2010 Prelims: 3
- AIPMT 2009 Prelims: 5
- AIPMT 2008 Prelims: 3
- AIPMT 2007 Prelims: 3
- AIPMT 2005 Prelims: 1
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