Microbes in Human Welfare NEET Notes 2027: Key Points and PDF

Microbes in Human Welfare is Chapter 8 of NCERT Class 12 Biology and part of Unit 8, Biology and Human Welfare, of the NEET UG syllabus. These notes cover microbes in household products, industrial products such as antibiotics, acids and enzymes, sewage treatment, biogas, biocontrol agents and biofertilisers, with organism-product tables and a free notes PDF.

Microbes in Human Welfare NEET Notes

Section-wise key points from NCERT Chapter 8, organism-product tables, high-yield facts and common mistakes for NEET 2027 revision.

Microbes in Human Welfare at a Glance

The topic list follows the NEET UG 2026 syllabus released by the National Medical Commission (NMC) on 22 December 2025, which stays the reference until the 2027 syllabus is out. The full list is on the NEET syllabus page.

Where are microbes found?

Microbes are present everywhere, in soil, water, air and inside plants and animals, even where no other life can exist.

• Extreme sites: deep inside geysers (thermal vents) at up to 100 °C, deep in the soil, under thick snow and in highly acidic environments.
• Microbes include protozoa, bacteria, fungi, microscopic plant and animal viruses, viroids and prions (proteinaceous infectious agents).
• Bacteria and many fungi grow on nutritive media as colonies visible to the naked eye.
• Not all microbes are harmful; many are useful to humans in diverse ways.

Microbes in Household Products

Curd, idli and dosa batter, bread, toddy and cheese are all made with the help of microbes.

Microbes are also used to ferment fish, soyabean and bamboo shoots to make foods.

Microbes in Industrial Products

Industrial production uses microbes grown in very large vessels called fermentors to make beverages, antibiotics, acids, enzymes and other bioactive molecules.

Fermented Beverages

• Saccharomyces cerevisiae, called brewer’s yeast here, ferments malted cereals and fruit juices to produce ethanol.
• Wine and beer are produced without distillation; whisky, brandy and rum are produced by distilling the fermented broth.

Antibiotics

• Antibiotics are chemicals produced by some microbes that kill or retard the growth of other, disease-causing microbes.
• Penicillin was the first antibiotic, a chance discovery: Alexander Fleming, working on Staphylococci, saw that a mould in an unwashed culture plate stopped their growth, and named the chemical after the mould Penicillium notatum.
• Ernest Chain and Howard Florey established its full potential; it was used extensively for soldiers wounded in World War II. Fleming, Chain and Florey shared the Nobel Prize in 1945.
• Antibiotics improved treatment of plague, whooping cough, diphtheria and leprosy.

Chemicals, Enzymes and Other Bioactive Molecules

How do microbes treat sewage?

Sewage, the municipal waste water rich in organic matter and microbes, is treated in sewage treatment plants (STPs) by heterotrophic microbes naturally present in it, in two stages.

• BOD (biochemical oxygen demand) is the amount of oxygen that would be consumed if all organic matter in one litre of water were oxidised by bacteria. It is an indirect measure of organic matter: the greater the BOD, the more polluting the water.
• A small part of the activated sludge is pumped back into the aeration tank as inoculum; the major part goes to anaerobic sludge digesters.
• In the digesters, anaerobic bacteria digest the bacteria and fungi of the sludge, producing methane, hydrogen sulphide and carbon dioxide, which form biogas.
• The secondary effluent is generally released into rivers and streams.
• The Ministry of Environment and Forests started the Ganga Action Plan and Yamuna Action Plan to build sewage treatment plants so that only treated sewage enters these rivers.

Microbes in Production of Biogas

Biogas is a mixture of gases, predominantly methane, produced by microbial activity and used as fuel.

• Methanogens, such as Methanobacterium, grow anaerobically on cellulosic material and produce large amounts of methane along with CO2 and H2.
• They are found in the anaerobic sludge of sewage treatment and in the rumen of cattle, where they help break down cellulose. Cattle dung (gobar) is rich in them, so biogas is also called gobar gas.
• A biogas plant has a concrete tank 10 to 15 feet deep fed with dung slurry, a floating cover that rises as gas forms, an outlet pipe for gas and another outlet for spent slurry, which can be used as fertiliser.
• Biogas is used for cooking and lighting, mostly in rural areas.
• The technology was developed in India mainly through the Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC).

Microbes as Biocontrol Agents

Biocontrol is the use of biological methods to control plant diseases and pests, reducing dependence on toxic chemical insecticides and pesticides.

• Organic farmers keep pests at manageable levels through checks and balances in the ecosystem rather than eradicating them, since beneficial predators and parasites depend on them.
• Ladybird beetles control aphids; dragonflies control mosquitoes.

Microbes as Biofertilisers

Biofertilisers are organisms that enrich the nutrient quality of the soil; the main sources are bacteria, fungi and cyanobacteria.

Most-asked Facts for NEET: Microbes in Human Welfare

Revise these one-line facts from the NCERT chapter just before the exam.

• LAB (Lactobacillus) convert milk to curd and increase its vitamin B12.
• Baker’s and brewer’s yeast are the same species: Saccharomyces cerevisiae.
• Swiss cheese holes: CO2 from Propionibacterium sharmanii; Roquefort cheese is ripened by a fungus.
• Wine and beer are not distilled; whisky, brandy and rum are distilled.
• Penicillin, the first antibiotic, comes from Penicillium notatum; Nobel Prize 1945 to Fleming, Chain and Florey.
• Citric acid: Aspergillus niger; acetic acid: Acetobacter aceti; butyric acid: Clostridium butylicum.
• Streptokinase (Streptococcus) is a clot buster; cyclosporin A (Trichoderma polysporum) is an immunosuppressant.
• Statins come from Monascus purpureus and lower blood cholesterol.
• Pectinases and proteases clarify fruit juices; lipases are used in detergents.
• Secondary sewage treatment lowers BOD using flocs in aeration tanks.
• Activated sludge is partly recycled as inoculum; the rest goes to anaerobic sludge digesters.
• Biogas is mainly methane, made by methanogens such as Methanobacterium; developed in India by IARI and KVIC.
• Bt toxin kills caterpillars in the larval gut.
• Baculoviruses used for biocontrol belong to genus Nucleopolyhedrovirus.
• Glomus forms mycorrhiza and supplies phosphorus; Anabaena, Nostoc and Oscillatoria fix nitrogen.

Common Mistakes to Avoid

Watch for these mix-ups when you answer questions on this chapter.

• Mixing up Trichoderma roles. Trichoderma polysporum gives cyclosporin A; Trichoderma species are also biocontrol agents of plant pathogens.
• Swapping acid producers. Aspergillus niger (a fungus) makes citric acid; Acetobacter aceti (a bacterium) makes acetic acid.
• Saying wine or beer is distilled. Only whisky, brandy and rum are made by distillation.
• Thinking a higher BOD means cleaner water. A higher BOD means more organic matter and more polluting potential.
• Placing biogas production in the aeration tank. Biogas is produced in anaerobic sludge digesters.
• Confusing primary sludge with activated sludge. Primary sludge settles in primary treatment; activated sludge is the settled bacterial flocs after secondary treatment.
• Calling Azotobacter symbiotic. Azotobacter and Azospirillum are free-living; Rhizobium is symbiotic.
• Saying mycorrhiza fixes nitrogen. The fungal symbiont absorbs phosphorus for the plant.
• Mixing up the organisms in the penicillin story. Fleming was working on Staphylococci bacteria, and the mould was Penicillium notatum.
• Thinking Bt kills all insects. Bt toxin kills butterfly caterpillars and leaves other insects unharmed.

Microbes in Human Welfare Notes PDF and Related Pages

Download the AglaSem notes for Microbes in Human Welfare (key notes and important questions with answers) free: View PDF

• All chapters: NEET Biology notes
• Full topic list: NEET syllabus
• Practice: NEET question papers
• Source text: NCERT Chapter 8 (NCERT, Class 12 Biology)

NEET Biology Notes: All Chapters

Botany

• The Living World
• Biological Classification
• Plant Kingdom
• Cell: The Unit of Life
• Plant Growth and Development
• Anatomy of Flowering Plants
• Cell Cycle and Cell Division
• Respiration in Plants
• Photosynthesis in Higher Plants
• Morphology of Flowering Plants
• Principles of Inheritance and Variation
• Microbes in Human Welfare
• Sexual Reproduction in Flowering Plants
• Molecular Basis of Inheritance
• Organisms and Populations
• Ecosystem
• Biodiversity and Conservation

Zoology

• Animal Kingdom
• Biomolecules
• Breathing and Exchange of Gases
• Excretory Products and their Elimination
• Body Fluids and Circulation
• Structural Organisation in Animals
• Locomotion and Movement
• Reproductive Health
• Chemical Coordination and Integration
• Neural Control and Coordination
• Evolution
• Human Health and Disease
• Human Reproduction
• Biotechnology and its Applications
• Biotechnology: Principles and Processes

All chapters with their notes PDFs are on the NEET Biology notes page.

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