MICROBES IN HUMAN WELFARE · Comparison Tables

1. Household products: microbes and roles

Everyday products formed with microbial help
Product	Microbe / process	NCERT point
Curd	Lactobacillus (LAB)	Converts milk sugar to lactic acid, coagulates milk proteins and increases vitamin B₁₂.
Dough	Saccharomyces cerevisiae (baker's yeast)	Produces CO₂, causing dough to rise.
Toddy	Natural yeast fermentation	Fermented sap from palms.
Cheese	Specific microbes	Swiss cheese: Propionibacterium shermanii; Roquefort: Penicillium roqueforti.

2. Fermented beverages vs industrial products

Microbial fermentation in industry
Feature	Fermented beverages	Industrial products
Typical organism	Yeast, mainly Saccharomyces cerevisiae	Selected bacteria, fungi and yeasts in fermenters
Substrate	Malted cereals or fruit juices	Large-volume nutrient medium under controlled conditions
Products	Wine and beer; distillation gives whisky, brandy and rum	Antibiotics, organic acids, enzymes, vitamins and bioactive molecules
Control	Fermentation of sugars	pH, temperature, aeration, foam and substrate concentration are monitored

3. Antibiotics vs bioactive molecules

Useful microbial metabolites
Feature	Antibiotics	Bioactive molecules
Meaning	Chemicals produced by microbes that kill or retard other microbes.	Microbial products used for a specific physiological or therapeutic effect.
Examples	Penicillin from Penicillium notatum.	Statins, cyclosporin A and streptokinase.
Action	Used chiefly against bacterial infections; misuse can select resistant bacteria.	Statins lower blood cholesterol; cyclosporin A suppresses immunity; streptokinase removes clots.
Sources in NCERT	Penicillin discovered by Alexander Fleming; later mass-produced.	Monascus purpureus, Trichoderma polysporum and Streptococcus, respectively.

4. Major organic acids and their microbes

High-yield industrial products
Product	Microorganism	Use / association
Citric acid	Aspergillus niger	Organic acid produced commercially.
Acetic acid	Acetobacter aceti	Organic acid / vinegar-related fermentation.
Butyric acid	Clostridium butylicum	Organic acid produced by anaerobic bacteria.
Lactic acid	Lactobacillus	Produced during milk fermentation.

5. Microbial enzymes and their applications

Enzymes used outside the microbe
Enzyme	Source	Application
Lipases	Microbes	Detergent formulations; remove oily stains.
Pectinases and proteases	Microbes	Clarify bottled fruit juices.
Streptokinase	Streptococcus	Clot buster; modifies plasminogen to dissolve blood clots.
Cyclosporin A	Trichoderma polysporum	Immunosuppressant used in organ transplantation.

6. Primary vs secondary sewage treatment

Stages of municipal wastewater treatment
Feature	Primary treatment	Secondary (biological) treatment
Nature	Physical removal of particles by filtration and sedimentation.	Biological oxidation of organic matter by microbes.
Main output	Primary sludge and primary effluent.	Activated sludge and treated effluent with reduced BOD.
Key agents	Screens, grit chamber and sedimentation tank.	Flocs of bacteria with fungal filaments in aeration tanks.
Further handling	Primary effluent enters aeration tank.	Part of activated sludge inoculates the tank; remainder enters anaerobic sludge digester.

7. Aerobic flocs vs anaerobic sludge digesters

Microbes in sewage treatment
Feature	Aerobic flocs	Anaerobic sludge digester
Condition	Air is pumped into aeration tank.	Oxygen-free digestion of sludge.
Microbes	Bacteria associated with fungal filaments.	Anaerobic bacteria, including methanogens.
Main effect	Consumes organic matter and lowers BOD.	Digesters release methane, H₂S and CO₂ - biogas.
Exam cue	Flocs are masses of bacteria with fungal filaments.	Methanogens also occur in rumen of cattle.

8. BOD vs COD

Measures of pollution load
Feature	BOD	COD
Full form	Biochemical oxygen demand.	Chemical oxygen demand.
Measures	Oxygen needed by aerobic microbes to decompose organic matter.	Oxygen equivalent needed to chemically oxidise oxidisable pollutants.
Interpretation	Higher BOD means more biodegradable organic pollution.	Usually includes both biodegradable and non-biodegradable oxidisable matter.
NCERT emphasis	Secondary treatment reduces BOD before effluent is released.	Useful broader pollution indicator; distinguish it from BOD.

9. Biocontrol agents vs chemical pesticides

Biological control in agriculture
Feature	Biocontrol agents	Chemical pesticides
Basis	Natural predators, parasites and pathogens suppress pests.	Chemicals kill or deter pest organisms.
Examples	Bacillus thuringiensis (Bt), baculoviruses, ladybird beetles and dragonflies.	Synthetic insecticides and other pesticides.
Specificity	Often target-specific; Bt toxin acts after ingestion by susceptible insect larvae.	May affect non-target organisms.
Approach	Core component of integrated pest management.	Can leave residues and create resistance problems.

10. Biofertilisers: nitrogen-fixers and mycorrhiza

Microbes that improve nutrient availability
Feature	Nitrogen-fixing microbes	Mycorrhiza
Examples	Rhizobium, Azotobacter, Azospirillum, cyanobacteria such as Anabaena and Nostoc.	Fungal association with roots, e.g. Glomus.
Association	Rhizobium forms root nodules in legumes; some are free-living.	Symbiotic association of fungus and plant root.
Benefit	Converts atmospheric nitrogen into usable forms.	Improves phosphate uptake; increases tolerance to drought and root pathogens.
Other NCERT point	Anabaena associates with Azolla in paddy fields.	Reduces need for phosphate fertiliser.