Microbes in Human Welfare
Microbes (protozoa, bacteria, fungi, microscopic plant and animal viruses, viroids and prions) are present everywhere - in soil, water, air, inside our bodies, and even at extreme sites. Not all microbes are pathogenic; many are very useful to human beings.
Household products
- Curd: Lactic acid bacteria (LAB) such as Lactobacillus grow in milk, produce acids that coagulate and partially digest milk proteins, and increase vitamin B12.
- Idli/dosa dough: fermented by bacteria; the puffed-up look is due to CO2.
- Bread: fermented by baker's yeast, Saccharomyces cerevisiae.
- Cheese: holes in Swiss cheese are due to large amounts of CO2 from Propionibacterium sharmanii; Roquefort cheese is ripened by a specific fungus.
- Toddy: traditional southern Indian drink made by fermenting palm sap.
Industrial products
- Fermented beverages: Saccharomyces cerevisiae (brewer's yeast) ferments malted cereals/fruit juices to ethanol. Wine and beer = no distillation; whisky, brandy, rum = with distillation.
- Antibiotics: chemicals produced by microbes that kill or retard the growth of disease-causing microbes. Penicillin (first antibiotic) was discovered by Alexander Fleming from the mould Penicillium notatum; developed by Chain and Florey (Nobel Prize 1945).
- Organic acids/enzymes/bioactive molecules: citric acid (Aspergillus niger), acetic acid (Acetobacter aceti), butyric acid (Clostridium butylicum), lactic acid (Lactobacillus), ethanol (Saccharomyces cerevisiae); lipases (detergents), pectinases and proteases (juice clarification), streptokinase (clot buster), cyclosporin A (Trichoderma polysporum, immunosuppressant), statins (Monascus purpureus, cholesterol-lowering).
Sewage treatment
Sewage (municipal waste-water) is treated by heterotrophic microbes naturally present in it, in two stages: primary (physical removal of particles by filtration and sedimentation) and secondary/biological (aerobic microbes form flocs, reduce BOD; flocs settle as activated sludge; major part digested anaerobically in sludge digesters producing biogas).Biogas
A mixture of gases (predominantly methane) produced by methanogens (e.g. Methanobacterium) growing anaerobically on cellulosic material. Found in anaerobic sludge and in cattle rumen. Cattle dung (gobar) is used to make biogas (gobar gas). Technology developed in India by IARI and KVIC.Biocontrol agents
- Bacillus thuringiensis (Bt): controls butterfly caterpillars.
- Trichoderma: free-living fungus controlling plant pathogens.
- Baculoviruses (genus Nucleopolyhedrovirus): species-specific narrow-spectrum insecticides, used in IPM.