Microbes in Human Welfare
Class 12 Biology · Biology · Chapter 8
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Summary
This chapter highlights the beneficial roles of microbes in human life across food, industry, agriculture and the environment. In household products, microbes such as Lactobacillus convert milk to curd, yeast (Saccharomyces cerevisiae) leavens dough and ferments to produce bread, and microbes are used in making cheese, idli, dosa and toddy. In industry, microbes produce fermented beverages (wine, beer, whisky), antibiotics (penicillin from Penicillium notatum, discovered by Alexander Fleming), organic acids (citric acid, acetic acid, butyric acid), enzymes (lipases, pectinases, streptokinase, cyclosporin A, statins) and other bioactive molecules. In sewage treatment, microbes act in primary and secondary (biological) treatment, with activated sludge and anaerobic sludge digesters producing biogas (methane). Microbes are used in biogas production (methanogens like Methanobacterium in gobar gas plants) and as biofertilisers (Rhizobium, Azospirillum, Azotobacter, mycorrhiza like Glomus, and cyanobacteria like Anabaena and Nostoc) that enrich soil nutrients. They also serve as biocontrol agents (Bacillus thuringiensis, Trichoderma, baculoviruses, ladybird and dragonfly) to manage pests and pathogens, reducing reliance on chemical pesticides. The chapter emphasises sustainable and eco-friendly applications of microbes for human welfare.
Microbes in household productsMicrobes in industrial productsMicrobes in sewage treatmentMicrobes in biogas productionMicrobes as biofertilisersMicrobes as biocontrol agents
Key terms
Fermentation
The anaerobic breakdown of sugars by microbes producing products such as alcohol, acids and gases.
Antibiotic
A chemical substance produced by a microbe that kills or inhibits the growth of other microbes, such as penicillin.
Biogas
A mixture of gases (predominantly methane) produced by microbial activity, used as fuel.
Biofertiliser
An organism that enriches the nutrient quality of soil, such as Rhizobium, Azotobacter, cyanobacteria and mycorrhiza.
Biocontrol agent
A biological agent used to control plant pests and pathogens, such as Bacillus thuringiensis and Trichoderma.
Activated sludge
The sediment of microbe-rich flocs in secondary sewage treatment that decomposes organic matter.
Extra questions & answers
Try one from this chapter
Curd is formed from milk by the action of: