08Class 12 Biology
Microbes in Human Welfare short notes
Short notes on how microbes help us: in food, industry, sewage treatment, biogas, pest control and fertilisers. Mostly name-and-use facts.
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Food and drink
- Lactobacillus turns milk into curd, adding vitamin B12.
- Saccharomyces cerevisiae (baker's yeast) raises bread dough, and also ferments drinks.
- Propionibacterium sharmanii puts the big holes in Swiss cheese.
- Wine and beer aren't distilled, while whisky and rum are.
Industrial products
- Citric acid: Aspergillus niger.
- Acetic acid: Acetobacter aceti.
- Butyric acid: Clostridium butylicum.
- Lactic acid: Lactobacillus.
- Penicillin: Penicillium notatum, found by Fleming.
- Streptokinase: Streptococcus, used to dissolve clots.
- Cyclosporin A: Trichoderma polysporum, used to suppress immunity in transplants.
- Statins: Monascus purpureus, used to lower cholesterol.
- Lipases go in detergents, and pectinases clear fruit juice.
Sewage and biogas
- Primary treatment removes solids physically.
- Secondary treatment uses aerobic microbes and flocs, which lowers BOD.
- BOD measures organic matter, so higher BOD means more polluted water.
- Methanogens such as Methanobacterium make biogas, which is mostly methane.
Biocontrol and biofertilisers
- Bacillus thuringiensis (Bt) kills butterfly caterpillars.
- Ladybird beetles eat aphids, and dragonflies eat mosquitoes.
- Trichoderma controls plant pathogens, and baculoviruses target specific insects.
- Rhizobium fixes nitrogen in legume roots, and Azospirillum and Azotobacter fix it in soil.
- Mycorrhiza, such as Glomus, helps plants absorb phosphorus.
- Cyanobacteria such as Anabaena and Nostoc enrich paddy fields.
Where students slip up
- Mixing up cyclosporin (immune suppression) and streptokinase (clots).
- Thinking high BOD means clean water. It means the opposite.
- Mixing up the microbes for Swiss cheese and for curd.
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