Microbes In Human Welfare

• Microbes are also present deep inside geysers, soil, acidic environment.
• Some microbes are harmful whereas some are useful.

Microbes in Household Products:

1. Lactobacillus: Lactic Acid Bacteria (LAB)

• Grow in milk and convert it to curd, by producing acids that coagulate and partially digest milk proteins.
• Small amount of curd is added to fresh milk as inoculum (starter) containing millions of LAB, which multiply at suitable temperature and convert milk to curd having more vitamin B_12.
• Checks disease causing microbes in stomach.

2. Fermentation: Puffed appearance in some food items is due to CO₂ production.

• Dough in dosa and idli is fermented by bacteria.
• Dough in bread is fermented by baker’s yeast - saccharomyces cerevisiae.
• Toddy (traditional drink of South India) is made by fermenting sap from palms.
• Microbes also ferment fish, soyabean and bamboo-shoots to make food.
• Cheese - oldest food item in which microbes were used.
• Large holes in Swiss cheese are due to bacterium Propionibacterium sharmanii.
• Roquefort cheese: Ripened by growing fungi on them.

Microbes in industrial Products: eg. in Beverages and antibiotics.

• Microbes are grown in large vessels - fermentors.

1. Fermented Beverages:

• Brewer’s yeast is used in fermenting malted cereals and fruit juices to produce ethanol.
• Wine and beer - produced without distillation, whisky, brandy, rum -produced by distillation.

2. Antibiotics:

• In Greek, Anti means against and bio means life - against life (in context to pathogens); pro life (in context to human being).
• Antibiotic: Chemical substances produced by microbes which can kill or retard growth of other microbes.
• Penicillin: First antibiotic discovered by Alexander Fleming while working on Staphylococci bacteria.
• He observed mould growing on unwashed culture plate around which bacteria couldn’t grow as mould secreted chemical - penicillin. Mould was Penicillin notatum. Its full potential was established by Ernest Chain and Howard Florey. It was used to treat American soldiers in World War II.
• Fleming, Chain and Florey were awarded nobel prize in 1945.
• Antibiotics treated diseases like plague, whooping cough (kali khansi), diphtheria (gal ghotu) and leprosy (kusht rog).

3. Chemicals, Enzymes and other Bioactive Molecules:

• Yeast (Saccharomyces cerevisiae) - ethanol.
• Aspergillus niger (fungus) - citric acid
• Acetobacter aceti (bacterium) - acetic acid
• Clostridium butylicum (bacterium) - butyric acid
• lactobacillus (bacterium) - lactic acid
• Lipase - detergent formulation (removing oily stains from laundry)
• Pectinase and protease - clear bottled fruit juices in market.
• Streptococcus - streptokinase (clot buster - remove clots from blood vessels in myocardial infarction).
• Trichoderma polysporum (fungus) - cyclosporin A (immunosuppressive in organ transplant).
• Monascus purpureus (yeast) - statins (blood cholesterol lowering agent, acts as competitively inhibiting enzyme responsible for cholesterol synthesis).

Microbes in Sewage Treatment:

• Major component of waste water - human excreta. This municipal waste water is called sewage, which contains organic matter and microbes (pathogenic).
• This is treated by sewage treatment plant to make it less polluting, which is mainly done by heterotrophic microbes naturally present in sewage.

1. Primary treatment: Physical removal of particles (filtration and sedimentation).

• Floating debris is removed by sequential filtration and grit (soil and pebbles) by sedimentation.
• Primary Sludge: All solid that settles.
• Supernatant forms effluent which is taken for secondary treatment.

2. Secondary treatment/Biological treatment:

• Effluents are passed into large aeration tank where its constantly agitated mechanically and air is pumped into it. It allows rapid growth of aerobic microbes as flocs (mass of bacteria with fungal filaments to form mesh like structure).
• They reduce BOD (biochemical oxygen demand) of effluent.
• BOD: Amount of O₂ that would be consumed if all organic
• matter in 1l water were oxidised by bacteria. It measures rate of O₂ uptake by microbes, organic matter present in water. Greater BOD, more is its polluting potential.

• Once BOD is reduced, effluent is passed to settling tank where bacterial floes are allowed to sediment and called activated sludge.
• Some amount of activated sludge is pumped to aeration tank to serve as inoculum whereas remaining sludge in pumped to large tank - anaerobic sludge digestor.
• Here anaerobic bacteria digest bacteria and fungi and produce mixture of gases like methane, hydrogen sulphide and carbon dioxide forming biogas (source of energy as inflammable). Now efffluent is released into water bodies.
• The Ministry of Environment and Forests has initiated Ganga Action Plan and Yamuna Action Plan under which its proposed to build sewage treatment plants so that only treated sewage may be discharged into rivers.

Microbes in’ production of Biogas:

• Biogas: Mixture of gases produced by microbial activity which may be used as fuel.
• Type of gas produced depends on microbes and organic substrates they utilise. eg. anaerobic bacteria growing on cellulosic material produce methane + CO₂ + H₂.
• These are called methanogens (one such is Methanobacterium). They are found in rumen of cattles where they help in breakdown of cellulose and play important role in nutrition of cattle. Thus excreta of cattle (gobar) is rich in these bacteria. So, dung can be used for generation of biogas ® gobar gas.

Biogas plant:

• It has concrete tank (10 - 15 feet deep) in which bio waste is collected and slurry of dung is fed.
• Floating cover is placed over slurry which keeps on rising as gas is produced. It has an outlet connected to a pipe to supply biogas to nearby houses.
• Spent slurry is removed through another outlet and used as fertiliser.
• Its build more often in rural areas due to availability of cattle dung.
• This biogas is used for cooking and lightning.
• This technology was developed by Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).

Microbes as Biocontrol Agents: Reduce dependence on toxic chemicals.

• Biocontrol: Use of biological methods for controlling plant diseases and pests.
• Today, these are tackled by insecticides, pesticides which are toxic and pollute environment.
• Organic farmer believes biodiversity furthers health (more variety a land has, more sustainable it is). So, he works to create system in which pests aren’t eradicated but kept at manageable level by system of checks and balance.
• Conventional farming method often kills both useful and harmful life forms by use of chemicals.

1. Ladybird (beetle with red and black markings) and Dragonflies are used to get rid of aphids and mosquitoes respectively.

2. Bacillus thuringiensis (Bt): Control butterfly caterpillars. (Bt Cotton)

• They are available in sachets as dried spores mixed with water and sprayed on plants (brassicas and fruit trees) where they are eaten by insect larvae.
• Toxin is released in gut of larvae and kills it.
• By genetic engineering Bt gene is introduced into plants which become resistant to attack by insect pests. eg. Bt cotton.

3. Trichoderma: Free living fungus in root ecosystem.

4. Baculovirus: Pathogen attacking insect and arthropods. Majority of them belong to genus Nucleopolyhedrovirus.

• They have narrow spectrum insecticidal application and have no negative impacts on plants, mammals, bird etc.
• Its desirable when beneficial insects are being preserved in integrated pest management (IPM) programme.

Microbes as Biofertilisers: eg. bacteria, fungi, cyanobacteria.

• Biofertilisers: Organisms that enrich nutrient quality of soil.

1. Bacteria:

• Rhizobium in symbiotic association with nodules on roots of leguminous plants, fix atmospheric N₂ into organic forms.
• Other bacteria fixing N₂ - Azospirillum and Azotobacter (free living in soil), thus enriching soil with N₂.

2. Fungi: Form symbiotic association with plant (mycorrhiza).

• Mainly members of genus Glomus.
• Fungal symbiont - absorb phosphorus from soil and pass to plant.
• Increase plant growth and development - tolerance to salinity and drought, resistance to root - borne pathogen.

3. Cyanobacteria: Autotrophic microbes in aquatic and terrestrial environments.

• Fix atmospheric nitrogen eg. Anabaena, Nostoc, Oscillatoria
• Add organic matter to soil and increase its fertility.
• Serve as important biofertiliser in paddy fields.