I. INTRODUCTION — MICROBES: OVERVIEW
A DISTRIBUTION OF MICROBES
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| FEATURE | DETAIL |
|---|---|
| Presence | Everywhere — soil, water, air, inside bodies of humans, animals & plants ⭐ |
| Extreme habitats | Deep inside geysers (thermal vents, temp up to 100°C), deep in soil, under layers of snow (metres thick), highly acidic environments ⭐ |
| Key point | Present even where NO other life-form could possibly exist ⭐ |
B DIVERSITY OF MICROBES
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| FEATURE | DETAIL |
|---|---|
| Include | Protozoa, Bacteria, Fungi, Microscopic animal & plant viruses, Viroids, Prions ⭐ |
| Prions | Proteinaceous infectious agents ⭐ |
| Colony formation | Bacteria & many Fungi can be grown on nutritive media to form colonies → visible to naked eyes ⭐ |
C MICROSCOPIC MAGNIFICATION REFERENCE
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| ORGANISM | MAGNIFICATION |
|---|---|
| Rod-shaped Bacteria | 1,500 X |
| Spherical-shaped Bacteria | 1,500 X |
| Rod-shaped Bacteria (showing flagella) | 50,000 X |
| TMV (Rod-shaped virus) | 1,00,000 – 1,50,000 X |
D KEY STATEMENT
🔑 Not all microbes are pathogenic — many are very useful to human beings. We use microbes and microbially derived products almost every day.
II. MICROBES IN HOUSEHOLD PRODUCTS
⚡ EXAM TRAP: NEET 2025
Microbes used in household products = Lactobacillus (curd), Saccharomyces cerevisiae (bread, beverages) and Propionibacterium sharmanii (Swiss cheese); Aspergillus niger (citric acid) and Trichoderma polysporum (cyclosporin A) are INDUSTRIAL microbes, not household ones.
A CURD PRODUCTION
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| FEATURE | DETAIL |
|---|---|
| Microbe | Lactobacillus & others — commonly called Lactic Acid Bacteria (LAB) ⭐⭐ |
| Process | LAB grow in milk → convert it to curd ⭐ |
| Mechanism | During growth, LAB produce acids that coagulate & partially digest milk proteins ⭐ |
| Inoculum / Starter | Small amount of curd added to fresh milk → contains millions of LAB → at suitable temperature → multiply → milk → curd ⭐ |
| Nutritional improvement | Curd improves nutritional quality by increasing Vitamin B₁₂ ⭐⭐⭐ |
| Additional benefit | In our stomach, LAB play a very beneficial role in checking disease-causing microbes ⭐⭐ |
⚡ EXAM TRAP: NEET 2018
Curd improves nutritional quality by increasing Vitamin B₁₂.
B DOUGH FERMENTATION
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| FEATURE | DETAIL |
|---|---|
| Foods made | Dosa & Idli — dough fermented by bacteria ⭐ |
| Puffed-up appearance | Due to production of CO₂ gas ⭐⭐ |
| Bread making | Dough fermented using Baker's yeast (Saccharomyces cerevisiae) ⭐ |
C TRADITIONAL DRINKS & FOODS
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| PRODUCT | DETAIL |
|---|---|
| Toddy | Traditional drink of some parts of Southern India ⭐; made by fermenting sap from palms ⭐ |
| Fermented foods | Fish, Soyabean, Bamboo-shoots → fermented by microbes ⭐ |
D CHEESE
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| TYPE | MICROBE | KEY FEATURE |
|---|---|---|
| Swiss Cheese | Propionibacterium sharmanii (Bacterium) ⭐⭐ | Large holes due to production of large amount of CO₂ ⭐⭐ |
| Roquefort Cheese | Specific Fungi grown on them ⭐ | Ripened by fungi → gives particular flavour ⭐ |
| General | Different varieties known by characteristic texture, flavour & taste | Specificity from the microbes used |
⚡ EXAM TRAP: NEET 2015
Propionibacterium sharmanii → large holes in Swiss Cheese (CO₂ production).
⚡ EXAM TRAP: NEET 2026
Large holes in Swiss cheese are produced due to a large amount of CO₂ released by Propionibacterium sharmanii — not by Lactobacillus, Clostridium butylicum or Trichoderma polysporum.
III. MICROBES IN INDUSTRIAL PRODUCTS
A FERMENTORS
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| FEATURE | DETAIL |
|---|---|
| Definition | Very large vessels used for growing microbes on an industrial scale ⭐ |
| Purpose | Production of industrial products — beverages, antibiotics, chemicals, enzymes |
B FERMENTED BEVERAGES
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| FEATURE | DETAIL |
|---|---|
| Microbe | Saccharomyces cerevisiae (Yeast) — also called Baker's yeast / Brewer's yeast ⭐⭐⭐ |
| Products | Wine, Beer, Whisky, Brandy, Rum, Bread ⭐ |
| Process | Fermenting malted cereals & fruit juices → produce Ethanol ⭐ |
| Commercial production of Ethanol | Saccharomyces cerevisiae ⭐⭐ |
Alcoholic Drinks Classification ⭐⭐⭐
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| CATEGORY | EXAMPLES | PROCESS |
|---|---|---|
| Without Distillation | Wine & Beer ⭐⭐ | Fermented broth used directly |
| With Distillation | Whisky, Brandy, Rum ⭐⭐ | Fermented broth is distilled |
⚡ EXAM TRAP: NEET 2024, 2019, 2017, 2015, 2012, 2011
Saccharomyces cerevisiae — Ethanol production; Baker's/Brewer's yeast.
⚡ EXAM TRAP: NEET TRAP
Wine & Beer = WITHOUT distillation; Whisky, Brandy, Rum = WITH distillation.
⚡ EXAM TRAP: NEET 2025
Beer is a non-distilled alcoholic beverage produced by yeast; Rum, Whisky and Brandy are all produced with distillation of the fermented broth.
C ANTIBIOTICS
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| FEATURE | DETAIL |
|---|---|
| Significance | Most significant discovery of 20th century ⭐ |
| Definition | Chemical substances produced by some microbes that kill or retard the growth of other (disease-causing) microbes ⭐⭐ |
| Etymology | Anti = 'against' + Bio = 'life' → 'against life' (of pathogens); but 'pro life' for human beings ⭐ |
| First antibiotic | Penicillin ⭐⭐ |
| Discovery | Alexander Fleming — chance discovery while working on Staphylococci bacteria ⭐⭐ |
| Observation | Mould growing in unwashed culture plate → Staphylococci could NOT grow around it ⭐ |
| Mould identified | Penicillium notatum ⭐⭐ |
| Full potential established by | Ernest Chain & Howard Florey ⭐⭐ |
| First major use | Treat American soldiers wounded in World War II ⭐ |
| Nobel Prize | Fleming, Chain & Florey — 1945 ⭐⭐ |
| Diseases treated | Plague, Whooping cough (Kali Khansi), Diphtheria (Gal Ghotu), Leprosy (Kusht Rog) ⭐ |
⚡ EXAM TRAP: NEET
Penicillin — first antibiotic; Penicillium notatum; discovered by Fleming; full potential by Chain & Florey; Nobel Prize 1945.
🔑 Antibiotics = chemicals produced by microbes that kill other microbes. Antibodies = proteins formed in the host to eliminate antigens. DO NOT CONFUSE.
D CHEMICALS, ENZYMES & BIOACTIVE MOLECULES
MASTER TABLE — Acid Producers ⭐⭐⭐
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| MICROBE | TYPE | PRODUCT |
|---|---|---|
| Aspergillus niger | Fungus ⭐ | Citric Acid ⭐⭐ |
| Acetobacter aceti | Bacterium ⭐ | Acetic Acid ⭐⭐ |
| Clostridium butylicum | Bacterium ⭐ | Butyric Acid ⭐⭐ |
| Lactobacillus | Bacterium ⭐ | Lactic Acid ⭐⭐ |
⚡ EXAM TRAP: RE-NEET 2024, NEET 2024, 2021, 2020, 2019, 2017, 2016, 2015, 2013, 2012
ALL four acid producers — MOST REPEATED NEET QUESTION from this chapter.
MASTER TABLE — Enzymes ⭐⭐
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| ENZYME | USE |
|---|---|
| Lipases | Used in detergent formulations → remove oily stains from laundry ⭐⭐ |
| Pectinases & Proteases | Used to clarify bottled fruit juices ⭐⭐ |
⚡ EXAM TRAP: NEET 2026
Lipases are used in detergent formulations.
MASTER TABLE — Bioactive Molecules ⭐⭐⭐
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| BIOACTIVE MOLECULE | SOURCE MICROBE | TYPE | USE |
|---|---|---|---|
| Streptokinase | Streptococcus (Bacterium) → modified by Genetic Engineering ⭐⭐ | Enzyme | 'Clot Buster' — removes clots from blood vessels of patients with myocardial infarction (heart attack) ⭐⭐⭐ |
| Cyclosporin A | Trichoderma polysporum (Fungus) ⭐⭐⭐ | Bioactive molecule | Immunosuppressive agent in organ-transplant patients ⭐⭐⭐ |
| Statins | Monascus purpureus (Yeast) ⭐⭐⭐ | Bioactive molecule | Blood-cholesterol lowering agent ⭐⭐⭐ |
Statins — Mechanism ⭐⭐
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| FEATURE | DETAIL |
|---|---|
| Mechanism of action | Competitively inhibiting the enzyme responsible for synthesis of cholesterol ⭐⭐ |
⚡ EXAM TRAP: NEET 2024, 2016
Streptokinase = Clot Buster; from Streptococcus; modified by genetic engineering; used for myocardial infarction.
⚡ EXAM TRAP: RE-NEET 2024, NEET 2024, 2022, 2019
Cyclosporin A = Immunosuppressive agent; from Trichoderma polysporum (Fungus).
⚡ EXAM TRAP: RE-NEET 2024, NEET 2020, 2016, 2015, 2012
Statins = Blood-cholesterol lowering agent; from Monascus purpureus (Yeast); competitively inhibits cholesterol synthesis enzyme.
⚡ EXAM TRAP: NEET 2026
Match-the-list: Streptokinase — removal of clots from the blood vessels; Statins — blood cholesterol-lowering agent; Lipases — detergent formulations; Cyclosporin A — immunosuppressive agent.
⚡ EXAM TRAP: NEET 2025
Streptokinase produced by the bacterium Streptococcus is used for removing clots from blood vessels.
⚡ EXAM TRAP: RE-NEET 2026
Streptokinase is the clot buster — not Penicillin, Cyclosporin A or Statins.
IV. MICROBES IN SEWAGE TREATMENT
A OVERVIEW
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| FEATURE | DETAIL |
|---|---|
| Sewage = | Municipal waste-water containing human excreta ⭐ |
| Contains | Large amounts of organic matter & microbes (many pathogenic) |
| Treatment done in | Sewage Treatment Plants (STPs) ⭐ |
| Purpose | Make sewage less polluting before discharge into rivers/streams |
| Treatment done by | Heterotrophic microbes naturally present in sewage ⭐⭐ |
| Two stages | (i) Primary Treatment & (ii) Secondary Treatment ⭐⭐ |
B PRIMARY TREATMENT (PHYSICAL REMOVAL)
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| STEP | PROCESS | WHAT IS REMOVED |
|---|---|---|
| 1. Filtration | Sequential filtration ⭐ | Floating debris removed ⭐ |
| 2. Sedimentation | Settling | Grit (soil & small pebbles) removed ⭐ |
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| PRODUCT | DEFINITION |
|---|---|
| Primary Sludge | All solids that settle during sedimentation ⭐ |
| Effluent | The supernatant (liquid above the sludge) ⭐ |
🔑 Effluent from primary settling tank → taken for secondary treatment.
⚡ EXAM TRAP: NEET 2017
Primary treatment = physical removal (filtration & sedimentation).
C SECONDARY TREATMENT (BIOLOGICAL TREATMENT)
Step-by-Step Process ⭐⭐⭐
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| STEP | EVENT |
|---|---|
| 1 | Primary Effluent → passed into LARGE AERATION TANKS ⭐ |
| 2 | Constantly agitated mechanically + Air pumped in ⭐ |
| 3 | Vigorous growth of useful AEROBIC MICROBES ⭐ |
| 4 | Form FLOCS ⭐⭐ |
| 5 | Microbes CONSUME major part of ORGANIC MATTER ⭐ |
| 6 | SIGNIFICANTLY REDUCES BOD ⭐⭐ |
| 7 | Effluent passed into SETTLING TANK |
| 8 | Bacterial flocs SEDIMENT = ACTIVATED SLUDGE ⭐⭐ |
| 9 | Small part of activated sludge → PUMPED BACK to aeration tank (as INOCULUM) ⭐⭐ |
| 10 | Remaining major part → ANAEROBIC SLUDGE DIGESTERS ⭐⭐ |
| 11 | Anaerobic bacteria digest bacteria & fungi in sludge |
| 12 | Produce BIOGAS (CH₄ + H₂S + CO₂) ⭐⭐ |
| 13 | Final effluent → Released into natural water bodies (rivers/streams) ⭐ |
Key Terms ⭐⭐⭐
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| TERM | DEFINITION |
|---|---|
| Flocs | Masses of bacteria associated with fungal filaments to form mesh-like structures ⭐⭐⭐ |
| BOD (Biochemical Oxygen Demand) | Amount of oxygen consumed if all organic matter in one litre of water were oxidised by bacteria ⭐⭐⭐ |
| BOD significance | BOD is a measure of organic matter present in water ⭐⭐ |
| BOD rule | Greater the BOD of waste water → more is its polluting potential ⭐⭐⭐ |
| Activated Sludge | Sediment of bacterial flocs in the settling tank ⭐⭐ |
| Inoculum | Small part of activated sludge pumped back into aeration tank ⭐ |
| Anaerobic Sludge Digesters | Large tanks where anaerobic bacteria digest the remaining sludge ⭐⭐ |
Gases Produced During Anaerobic Digestion ⭐⭐⭐
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| GAS | FORMULA |
|---|---|
| Methane | CH₄ ⭐ |
| Hydrogen Sulphide | H₂S ⭐ |
| Carbon Dioxide | CO₂ ⭐ |
🔑 These gases form Biogas → used as source of energy (inflammable).
⚡ EXAM TRAP: NEET 2020
Secondary treatment = biological treatment; activated sludge; flocs.
⚡ EXAM TRAP: NEET 2012
BOD = measure of organic matter; Greater BOD = more polluting potential.
⚡ EXAM TRAP: NEET 2014
Gases produced during digestion = CH₄, H₂S, CO₂.
D GOVERNMENT INITIATIVES
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| FEATURE | DETAIL |
|---|---|
| Ministry of Environment & Forests initiated | Ganga Action Plan & Yamuna Action Plan ⭐ |
| Purpose | Save major rivers from pollution by building more STPs |
| Problem | Untreated sewage often discharged directly into rivers → pollution → water-borne diseases |
V. MICROBES IN PRODUCTION OF BIOGAS
A BIOGAS — DEFINITION
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| FEATURE | DETAIL |
|---|---|
| Definition | A mixture of gases (predominantly CH₄ / Methane) produced by microbial activity → used as fuel ⭐⭐⭐ |
| Key gas | Methane (CH₄) — predominant component ⭐⭐ |
⚡ EXAM TRAP: NEET 2012
Biogas = mixture of gases, predominantly methane, produced by microbial activity, used as fuel.
B METHANOGENS
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| FEATURE | DETAIL |
|---|---|
| Definition | Bacteria that grow anaerobically on cellulosic material ⭐⭐ |
| Products | Large amounts of CH₄ along with CO₂ & H₂ ⭐⭐ |
| Common example | Methanobacterium ⭐⭐⭐ |
| Found in | Anaerobic sludge during sewage treatment ⭐ |
| Also present in | Rumen (a part of stomach) of cattle ⭐⭐⭐ |
| Role in Rumen | Help in breakdown of cellulose → important role in nutrition of cattle ⭐⭐ |
| Why cattle dung (gobar) is useful | Rich in methanogens → can be used for biogas generation ⭐ |
| Common name of biogas from cattle dung | Gobar gas ⭐ |
⚡ EXAM TRAP: NEET 2015
Methanogens (Methanobacterium) → grow anaerobically on cellulosic material → produce CH₄, CO₂, H₂.
🔑 Humans CANNOT digest cellulose (no cellulase enzyme); cattle can — due to methanogens in rumen.
C BIOGAS PLANT
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| FEATURE | DETAIL |
|---|---|
| Structure | Concrete tank (10–15 feet deep) ⭐ |
| Input | Bio-wastes collected + slurry of dung fed ⭐ |
| Floating cover | Placed over slurry → keeps rising as gas is produced ⭐ |
| Outlet | Connected to pipe → supplies biogas to nearby houses |
| Spent slurry | Removed through another outlet → used as fertiliser ⭐ |
| Location | More often built in rural areas (cattle dung available in large quantities) ⭐ |
| Uses | Cooking & Lighting ⭐⭐ |
D DEVELOPMENT OF BIOGAS TECHNOLOGY IN INDIA
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| ORGANISATION | FULL FORM |
|---|---|
| IARI | Indian Agricultural Research Institute ⭐⭐ |
| KVIC | Khadi & Village Industries Commission ⭐⭐ |
⚡ EXAM TRAP: NEET
Biogas technology in India developed mainly due to efforts of IARI & KVIC.
VI. MICROBES AS BIOCONTROL AGENTS
A OVERVIEW
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| FEATURE | DETAIL |
|---|---|
| Biocontrol = | Use of biological methods for controlling plant diseases & pests ⭐⭐ |
| Problem with chemical pesticides | Toxic & extremely harmful to humans & animals; pollute environment (soil, ground water), fruits, vegetables, crops ⭐ |
| Organic farming philosophy | Biodiversity furthers health ⭐; pests not eradicated but kept at manageable levels by checks & balances within ecosystem ⭐ |
| Advantage | Reduces dependence on toxic chemicals & pesticides ⭐ |
B MACROSCOPIC BIOCONTROL AGENTS
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| AGENT | CONTROLS |
|---|---|
| Ladybird (beetle with red & black markings) | Aphids ⭐⭐ |
| Dragonflies | Mosquitoes ⭐⭐ |
⚡ EXAM TRAP: NEET 2020
Ladybird → Aphids; Dragonflies → Mosquitoes.
C MICROBIAL BIOCONTROL AGENTS
1. Bacillus thuringiensis (Bt) ⭐⭐⭐
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| FEATURE | DETAIL |
|---|---|
| Type | Bacterium ⭐ |
| Controls | Butterfly caterpillars (Lepidopteran pests) ⭐⭐ |
| Available as | Dried spores in sachets ⭐ |
| Application | Mixed with water → sprayed onto vulnerable plants (brassicas, fruit trees) ⭐ |
| Mechanism | Eaten by insect larvae → toxin released in gut of larvae → larvae killed ⭐⭐ |
| Specificity | Kills caterpillars but leaves other insects unharmed ⭐ |
| Genetic engineering application | Bt toxin genes introduced into plants → plants resistant to insect pests → e.g., Bt-cotton ⭐⭐ |
⚡ EXAM TRAP: NEET 2013
Bacillus thuringiensis (Bt) = microbial biocontrol agent for butterfly caterpillars.
2. Trichoderma ⭐⭐
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| FEATURE | DETAIL |
|---|---|
| Type | Free-living Fungi ⭐⭐ |
| Habitat | Very common in root ecosystems ⭐⭐ |
| Function | Effective biocontrol agent of several plant pathogens ⭐⭐ |
| Use | Biological control in treatment of plant diseases ⭐ |
⚡ EXAM TRAP: NEET 2019, 2022
Trichoderma = free-living fungi in root ecosystems; biocontrol agent against plant pathogens.
⚡ EXAM TRAP: NEET TRAP
Trichoderma polysporum → Cyclosporin A (immunosuppressive); Trichoderma species (general) → biocontrol agent — Don't confuse the two!
3. Baculoviruses ⭐⭐⭐
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| FEATURE | DETAIL |
|---|---|
| Type | Pathogens that attack insects & other arthropods ⭐⭐ |
| Genus used as biocontrol | Nucleopolyhedrovirus ⭐⭐⭐ |
| Specificity | Species-specific, narrow spectrum insecticidal applications ⭐⭐⭐ |
| Safety | No negative impacts on plants, mammals, birds, fish, or even non-target insects ⭐⭐⭐ |
| Especially desirable when | (i) Beneficial insects being conserved for overall Integrated Pest Management (IPM) ⭐⭐ (ii) Ecologically sensitive area is being treated ⭐⭐ |
⚡ EXAM TRAP: NEET 2019, 2013, 2020, 2022
Baculoviruses → genus Nucleopolyhedrovirus; species-specific; narrow spectrum; no negative impact on non-target organisms; desirable for IPM & ecologically sensitive areas.
⚡ EXAM TRAP: NEET 2026
A biocontrol agent that forms part of an Integrated Pest Management programme must be species-specific and inactive on non-target organisms — not broad spectrum, not free-living, not symbiotic.
VII. MICROBES AS BIOFERTILISERS
A OVERVIEW
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| FEATURE | DETAIL |
|---|---|
| Biofertilisers = | Organisms that enrich the nutrient quality of the soil ⭐⭐⭐ |
| Main sources | Bacteria, Fungi & Cyanobacteria ⭐⭐ |
| Why needed | Overuse of chemical fertilisers → environmental pollution → push for organic farming ⭐ |
⚡ EXAM TRAP: NEET 2017, 2012
Biofertilisers = organisms that enrich nutrient quality of soil; sources = bacteria, fungi, cyanobacteria.
B BACTERIA AS BIOFERTILISERS
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| CATEGORY | EXAMPLES | FUNCTION |
|---|---|---|
| Symbiotic | Rhizobium ⭐⭐⭐ | Forms nodules on roots of leguminous plants; fixes atmospheric N₂ into organic forms ⭐⭐ |
| Symbiotic | Frankia ⭐ | Symbiotic N₂ fixer |
| Free-living | Azotobacter ⭐⭐ | Fixes atmospheric N₂ while free-living in soil → enriches nitrogen content of soil ⭐⭐ |
| Free-living | Azospirillum ⭐⭐ | Free-living N₂ fixer in soil ⭐ |
| Free-living | Beijerinckia ⭐ | Free-living N₂ fixer |
| Free-living | Rhodospirillum ⭐ | Free-living N₂ fixer |
⚡ EXAM TRAP: NEET TRAP
Azospirillum & Azotobacter = Free-living; Rhizobium & Frankia = Symbiotic.
⚡ EXAM TRAP: NEET 2026
Cyanobacteria and Rhizobium is the pair in which both microbes can be used as biofertilisers; Aspergillus and Rhizopus are not biofertilisers.
C FUNGI AS BIOFERTILISERS — MYCORRHIZA
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| FEATURE | DETAIL |
|---|---|
| Mycorrhiza = | Symbiotic association between Fungi & Roots of higher plants ⭐⭐⭐ |
| Common genus | Many members of genus Glomus form mycorrhiza ⭐⭐⭐ |
| Fungus provides to plant | (i) Absorbs Phosphorus from soil & passes to plant ⭐⭐⭐ (ii) Resistance to root-borne pathogens ⭐ (iii) Tolerance to salinity & drought ⭐ (iv) Overall increase in plant growth & development ⭐ |
| Plant provides to fungus | Shelter & Carbon ⭐⭐ |
⚡ EXAM TRAP: NEET 2012, 2020
Mycorrhiza = symbiotic association of fungi & plant roots; Glomus; fungi absorb phosphorus from soil; plant provides shelter & carbon.
D CYANOBACTERIA AS BIOFERTILISERS
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| FEATURE | DETAIL |
|---|---|
| Also called | Blue-Green Algae (BGA) ⭐ |
| Type | Autotrophic microbes ⭐ |
| Distribution | Widely distributed in aquatic & terrestrial environments ⭐ |
| N₂-fixing examples | Anabaena, Nostoc, Oscillatoria ⭐⭐⭐ |
| Important role | In paddy fields → serve as important biofertiliser ⭐⭐⭐ |
| Additional benefit | Add organic matter to soil → increase its fertility ⭐⭐ |
| Volvox | Green alga — NOT a nitrogen fixer ⭐⭐⭐ |
⚡ EXAM TRAP: NEET 2022
Cyanobacteria (Nostoc, Anabaena, Oscillatoria) = N₂-fixing; important biofertiliser in paddy fields.
⚡ EXAM TRAP: NEET 2025
Azotobacter, Oscillatoria, Anabaena and Nostoc all fix nitrogen; Volvox (a green alga) CANNOT fix nitrogen.
VIII. RAPID REVISION — KEY COMPARISON TABLES
TABLE 1: ALL Microbe–Product Associations ⭐⭐⭐
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| MICROBE | TYPE | PRODUCT / ROLE |
|---|---|---|
| Lactobacillus (LAB) | Bacterium | Curd (Lactic acid); ↑ Vitamin B₁₂ |
| Saccharomyces cerevisiae | Yeast (Fungus) | Ethanol, Bread, Wine, Beer, Whisky, Brandy, Rum |
| Propionibacterium sharmanii | Bacterium | Swiss Cheese (holes — CO₂) |
| Specific Fungi | Fungus | Roquefort Cheese (flavour) |
| Penicillium notatum | Fungus | Penicillin (first antibiotic) |
| Aspergillus niger | Fungus | Citric Acid |
| Acetobacter aceti | Bacterium | Acetic Acid |
| Clostridium butylicum | Bacterium | Butyric Acid |
| Streptococcus | Bacterium (genetically modified) | Streptokinase (Clot Buster) |
| Trichoderma polysporum | Fungus | Cyclosporin A (Immunosuppressive) |
| Monascus purpureus | Yeast | Statins (↓ Blood cholesterol) |
| Methanobacterium | Bacterium (Methanogen) | Biogas / Methane |
| Bacillus thuringiensis (Bt) | Bacterium | Biocontrol (butterfly caterpillars) |
| Trichoderma species | Fungus | Biocontrol (plant pathogens) |
| Nucleopolyhedrovirus | Baculovirus | Biocontrol (insects/arthropods) |
| Rhizobium | Bacterium | Biofertiliser (symbiotic N₂ fixer) |
| Azotobacter / Azospirillum | Bacterium | Biofertiliser (free-living N₂ fixer) |
| Glomus | Fungus | Mycorrhiza (Phosphorus absorption) |
| Anabaena / Nostoc / Oscillatoria | Cyanobacteria | Biofertiliser (N₂ fixer — paddy fields) |
TABLE 2: Primary vs Secondary Sewage Treatment ⭐⭐⭐
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| FEATURE | PRIMARY TREATMENT | SECONDARY TREATMENT |
|---|---|---|
| Type | Physical removal ⭐ | Biological removal ⭐ |
| Process | Filtration & Sedimentation | Aeration → Floc formation → BOD reduction |
| Removes | Floating debris, Grit (soil & pebbles) | Organic matter (dissolved / suspended) |
| Products | Primary sludge + Effluent | Activated sludge + Treated effluent |
| Microbes involved | No active microbial role | Aerobic microbes (flocs) + Anaerobic bacteria (digesters) |
| Key outcome | Removal of suspended solids | Significant reduction of BOD |
TABLE 3: Free-living vs Symbiotic Biofertilisers ⭐⭐⭐
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| CATEGORY | FREE-LIVING | SYMBIOTIC |
|---|---|---|
| Bacteria | Azotobacter, Azospirillum, Beijerinckia, Rhodospirillum | Rhizobium, Frankia |
| Fungi | — | Glomus (Mycorrhiza) |
| Cyanobacteria | Anabaena, Nostoc, Oscillatoria | — |
| Function | Fix N₂ in soil independently | Fix N₂ in association with plant roots |
TABLE 4: Three Biocontrol Agents ⭐⭐⭐
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| AGENT | TYPE | TARGET | KEY FEATURE |
|---|---|---|---|
| Bacillus thuringiensis (Bt) | Bacterium | Butterfly caterpillars (Lepidoptera) | Toxin released in larval gut → kills larvae; Bt genes → Bt-cotton |
| Trichoderma | Free-living Fungus | Plant pathogens | Common in root ecosystems |
| Baculoviruses (Nucleopolyhedrovirus) | Virus | Insects & Arthropods | Species-specific; narrow spectrum; no harm to non-targets; ideal for IPM |
TABLE 5: Alcoholic Beverages ⭐⭐
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| FEATURE | WITHOUT DISTILLATION | WITH DISTILLATION |
|---|---|---|
| Examples | Wine, Beer | Whisky, Brandy, Rum |
| Process | Fermented broth used directly | Fermented broth distilled |
| Microbe | S. cerevisiae | S. cerevisiae |
TABLE 6: Bioactive Molecules ⭐⭐⭐
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| MOLECULE | SOURCE | TYPE | USE |
|---|---|---|---|
| Streptokinase | Streptococcus (modified by genetic engg.) | Enzyme | Clot Buster (myocardial infarction) |
| Cyclosporin A | Trichoderma polysporum (Fungus) | Bioactive molecule | Immunosuppressive (organ transplant) |
| Statins | Monascus purpureus (Yeast) | Bioactive molecule | Blood-cholesterol lowering (competitive inhibition) |
TABLE 7: Mycorrhiza — Give & Take ⭐⭐
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| DIRECTION | WHAT IS EXCHANGED |
|---|---|
| Fungus → Plant | Phosphorus from soil; Pathogen resistance; Salinity & drought tolerance; ↑ Growth |
| Plant → Fungus | Shelter & Carbon |
TABLE 8: Key Organisations ⭐
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| ABBREVIATION | FULL FORM | ROLE |
|---|---|---|
| IARI | Indian Agricultural Research Institute | Biogas technology development in India |
| KVIC | Khadi & Village Industries Commission | Biogas technology development in India |
IX. COMMON EXAM TRAPS — QUICK REFERENCE
CONSOLIDATED PYQ Q&A TABLE ⭐⭐⭐
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| TRAP / QUESTION | CORRECT ANSWER |
|---|---|
| All microbes are harmful? | No — many are very useful to humans ⭐ |
| Microbes can be seen with naked eyes? | Yes — when grown as colonies on nutritive media ⭐ |
| Which microbe converts milk → curd? | Lactobacillus (LAB) ⭐ |
| Curd improves which vitamin? | Vitamin B₁₂ ⭐⭐ |
| LAB role in stomach? | Check disease-causing microbes ⭐ |
| Puffed-up dough due to? | CO₂ gas production ⭐ |
| Dosa/Idli dough fermented by? | Bacteria ⭐ |
| Bread dough fermented by? | Baker's yeast (S. cerevisiae) ⭐ |
| Toddy made from? | Fermenting sap from palms ⭐ |
| Holes in Swiss cheese due to? | CO₂ from Propionibacterium sharmanii ⭐⭐⭐ |
| Which microbes ARE household? | Lactobacillus, S. cerevisiae, P. sharmanii ⭐⭐⭐ |
| Which microbes are NOT household? | Aspergillus niger and Trichoderma polysporum ⭐⭐⭐ |
| Roquefort Cheese ripened by? | Fungi ⭐ |
| Baker's yeast = Brewer's yeast = ? | Saccharomyces cerevisiae ⭐⭐ |
| Non-distilled beverage produced by yeast? | Beer (also Wine) ⭐⭐⭐ |
| Rum, Whisky, Brandy? | Distilled ⭐⭐ |
| Fermentors = ? | Very large vessels for industrial-scale microbial growth ⭐ |
| First antibiotic? | Penicillin ⭐ |
| Penicillin discovered by? | Alexander Fleming (chance discovery) ⭐ |
| Penicillin from which mould? | Penicillium notatum ⭐ |
| Full potential of Penicillin established by? | Ernest Chain & Howard Florey ⭐ |
| Nobel Prize for Penicillin — year? | 1945 (Fleming + Chain + Florey) ⭐ |
| Penicillin first major use? | Treating American soldiers in WWII ⭐ |
| Antibiotics vs Antibodies? | Antibiotics = chemicals from microbes; Antibodies = proteins from host body ⭐⭐ |
| Citric acid from? | Aspergillus niger (Fungus) ⭐⭐ |
| Acetic acid from? | Acetobacter aceti (Bacterium) ⭐ |
| Butyric acid from? | Clostridium butylicum (Bacterium) ⭐ |
| Lactic acid from? | Lactobacillus (Bacterium) ⭐ |
| Ethanol commercially produced by? | Saccharomyces cerevisiae ⭐ |
| Lipases used in? | Detergent formulations (oily stains) ⭐⭐⭐ |
| Bottled juice clarified by? | Pectinases & Proteases ⭐ |
| Streptokinase — source? | Streptococcus (modified by genetic engineering) ⭐ |
| Which is the clot buster? | Streptokinase ⭐⭐⭐ |
| Streptokinase used for? | Removal of clots from blood vessels ⭐⭐⭐ |
| Cyclosporin A — source? | Trichoderma polysporum (Fungus) ⭐⭐ |
| Cyclosporin A used as? | Immunosuppressive agent ⭐⭐⭐ |
| Statins — source? | Monascus purpureus (Yeast) ⭐⭐ |
| Statins used for? | Lowering blood cholesterol ⭐⭐⭐ |
| Statins — mechanism? | Competitively inhibit enzyme for cholesterol synthesis ⭐⭐ |
| Sewage treatment done by? | Heterotrophic microbes naturally present in sewage ⭐ |
| Primary treatment = ? | Physical removal (filtration + sedimentation) ⭐ |
| Secondary treatment = ? | Biological treatment ⭐ |
| Flocs = ? | Masses of bacteria + fungal filaments → mesh-like structures ⭐⭐ |
| BOD stands for? | Biochemical Oxygen Demand ⭐ |
| BOD measures? | Organic matter in water ⭐ |
| Greater BOD means? | More polluting potential ⭐⭐ |
| Activated sludge = ? | Sediment of bacterial flocs in settling tank ⭐ |
| What is pumped back as inoculum? | Small part of activated sludge → back to aeration tank ⭐⭐ |
| Gases from anaerobic sludge digestion? | CH₄ + H₂S + CO₂ ⭐⭐ |
| Biogas = ? | Mixture of gases (predominantly CH₄) from microbial activity → used as fuel ⭐⭐ |
| Methanogens = ? | Bacteria growing anaerobically on cellulosic material → produce CH₄ ⭐ |
| Common methanogen? | Methanobacterium ⭐⭐ |
| Methanogens found in? | Anaerobic sludge + Rumen of cattle ⭐⭐ |
| Role in rumen? | Breakdown of cellulose → nutrition of cattle ⭐ |
| Can humans digest cellulose? | No ⭐ |
| Gobar gas = ? | Biogas from cattle dung ⭐ |
| Biogas plant depth? | 10–15 feet deep concrete tank ⭐ |
| Biogas used for? | Cooking & Lighting ⭐ |
| Biogas technology developed by? | IARI & KVIC ⭐⭐ |
| Ganga/Yamuna Action Plan by? | Ministry of Environment & Forests ⭐ |
| Biocontrol = ? | Biological methods for controlling plant diseases & pests ⭐ |
| Ladybird controls? | Aphids ⭐⭐ |
| Dragonflies control? | Mosquitoes ⭐⭐ |
| Bt full form? | Bacillus thuringiensis ⭐ |
| Bt controls? | Butterfly caterpillars ⭐ |
| Bt toxin released where? | In gut of larvae ⭐⭐ |
| Bt-cotton = ? | Bt toxin genes introduced into cotton plants ⭐ |
| Trichoderma — habitat? | Root ecosystems (free-living fungi) ⭐ |
| Baculoviruses — genus used? | Nucleopolyhedrovirus ⭐⭐ |
| Biocontrol agent for IPM must be? | Species-specific and inactive on non-target organisms ⭐⭐⭐ |
| Baculoviruses harm non-target organisms? | No — no negative impacts ⭐⭐ |
| IPM full form? | Integrated Pest Management ⭐ |
| Biofertilisers = ? | Organisms that enrich nutrient quality of soil ⭐⭐ |
| Main sources of biofertilisers? | Bacteria, Fungi, Cyanobacteria ⭐ |
| Pair where both are biofertilisers? | Cyanobacteria and Rhizobium ⭐⭐⭐ |
| Rhizobium — free-living or symbiotic? | Symbiotic (with leguminous plant roots) ⭐⭐ |
| Azotobacter — free-living or symbiotic? | Free-living ⭐⭐ |
| Mycorrhiza = ? | Symbiotic association of Fungi & Roots of higher plants ⭐⭐ |
| Common mycorrhizal genus? | Glomus ⭐⭐ |
| Fungi provide to plant in mycorrhiza? | Phosphorus (from soil) ⭐⭐⭐ |
| Plant provides to fungus in mycorrhiza? | Shelter & Carbon ⭐⭐ |
| N₂-fixing cyanobacteria examples? | Anabaena, Nostoc, Oscillatoria ⭐⭐ |
| Do Oscillatoria, Anabaena, Nostoc fix N₂? | Yes ⭐⭐ |
| Which organism cannot fix nitrogen? | Volvox ⭐⭐⭐ |
| Cyanobacteria important in which crop? | Paddy fields ⭐⭐ |
| Cyanobacteria also add? | Organic matter to soil → increase fertility ⭐ |
| T. polysporum vs Trichoderma species? | T. polysporum → Cyclosporin A; Trichoderma spp. → Biocontrol agent ⭐⭐ |
| Monascus purpureus is yeast or bacterium? | Yeast ⭐ |
| Aspergillus niger is fungus or bacterium? | Fungus ⭐ |
| Is S. cerevisiae used for both bread AND alcohol? | Yes — Baker's yeast = Brewer's yeast ⭐⭐ |
| Sedative and painkiller for post-surgery patients? | Morphine (cross-link Ch-7) ⭐⭐ |
⚡ EXAM TRAP: RE-NEET 2026
Morphine is used as an effective sedative and painkiller for treating post-surgery patients; interferon, antibiotics and anti-retroviral drugs are not. (Cross-link: Ch-7 Human Health and Disease.)