MICROBES IN HUMAN WELFARE

QUICK REVISION:MICROBES IN HOUSEHOLD PRODUCTS Lactobacillus or Lactic acid bacteria (LAB):-Convert milk to curd.-LAB produces acids that coagulate and partially digest the milk proteins.-A small amount of curd (which contains LAB) + fresh milk converts to curd. It also increases vitamin B12.-In stomach, LAB helps to check pathogens. Bacterial Fermentation (Anaerobic respiration)in dough is used to make foods such asdosa, idlietc. The puffed up appearance of dough is due to the production of CO2gas. Bakers Yeast (Saccharomyces cerevisiae):It is used to make bread by fermenting dough. Toddyis made by fermenting sap from palms. Microbes are used to ferment fish, soya bean and bamboo-shoots to make foods. Microbes are used to produce cheeses differing in flavor, taste and texture. E.g.-Large holes inSwiss cheeseare due to production of CO2byPropionibacterium sharmanii(a bacterium).-Roquefort cheeseis ripened by growing a specific fungus on them that gives them a particular flavor.MICROBES IN INDUSTRIAL PRODUCTSProduction of beverages, antibiotics etc on an industrial scale, requires growing microbes in very large vessels(fermentors).Fermented beverages-Saccharomyces cerevisiae (Brewers yeast)is used in the production of beverages by fermenting malted cereals and fruit juices to produce ethanol.-Wine & Beerare produced without distillation.-Whisky, Brandy & Rum are produced by distillation of fermented broth.Antibiotics-Chemical substances produced by some microbes and can kill or retard the growth of other disease-causing microbes.-They are used to treat plague, whooping cough, diphtheria, leprosy etc.-Penicillin:First antibiotic discovered byAlexander Fleming.He observed that a mould (Penicillium notatum) growing in unwashed culture plates around whichStaphylococcicould not grow. He extracted penicillin from it.-Earnest chainandHoward Floreyestablished its full potential as an effective antibiotic.-Fleming, Chain & Florey were awarded Nobel Prize (1945).Chemicals, enzymes and other bioactive molecules1. Organic acids:E.g.Aspergillus niger(a fungus) : Citric acidAcetobacter aceti(a bacterium) : Acetic acidClostridium butylicum(a bacterium) : Butyric acidLactobacillus(a bacterium) : Lactic acid2. Alcohol:Yeast (S. cerevisiae) is used to produce ethanol.3. Enzymes: Lipases:Used in detergent formulations. Help to remove oily stains from the laundry. Pectinases & Proteases:To clarify bottled juices. Streptokinase:Produced byStreptococcus.Used as a clot busterto remove clots from the blood vessels of patients who havemyocardial infarction.4. Cyclosporine A:produced byTrichoderma polysporum(fungus). Used as animmunosuppressive agentin organ transplant patients.5. Statins:Produced byMonascus purpureus(a yeast). Used asblood-cholesterol lowering agents. It inhibits the enzymes responsible for synthesis of cholesterol.MICROBES IN SEWAGE TREATMENTSewage (municipal waste-water) contains large amount of organic matter and microbes.Sewage is treated inSewage Treatment Plants (STPs)to make it less polluting. It includes 2 stages,1. Primary treatmentIt is the physical removal of particles. It includes1. Removal of floating debris by sequentialfiltration.2. Removal of the grit (soil & pebbles) bysedimentation.All solids that settle form theprimary sludgeand the supernatant form theprimaryeffluent.2. Secondary treatment (Biological treatment)Primary effluent is passed into large aeration tanks and constantly agitated. This allows vigorous growth of useful aerobic microbes intoflocs(masses of bacteria associated with fungal filaments to form mesh-like structures). These microbes consume the major part of the organic matter in the effluent. This reduces theBOD (Biochemical Oxygen Demand)of the effluent.BOD:Amount of O2consumed by bacteria to oxidize all organic matter in one litre of water. It is a measure of organic matter present in the water. The greater the BOD more is its polluting potential.

The effluent is then passed into a settling tank where the bacterialflocsare allowed to sediment. This sediment is calledactivated sludge.A small part of the activated sludge is pumped back into the aeration tank to serve as theinoculum.The remaining major part of the sludge is pumped into large tanks calledanaerobic sludge digesters.Here, some anaerobic bacteria digest the bacteria and fungi in the sludge by producing gases like CH4, H2S and CO2. These gases form the biogas.The effluent from secondary treatment plant is released into natural water bodies like rivers and streams.The Ministry of Environment & Forestshas initiatedGanga Action Plan&Yamuna Action Planto save from water pollution.MICROBES IN THE PRODUCTION OF BIOGAS-Biogas:Mixture of gases (mainly CH4) produced by the microbial activity. Biogas is used for cooking & lighting.-Methanogensgrow anaerobically on cellulosic material and produce CH4.E.g.Methanobacterium.-Methanobacteriumis found in theanaerobic sludgeandrumen of cattle(for cellulose digestion).-The dung of cattle(gobar)is rich in these bacteria. Dung can be used for generation of biogas(Gobar gas).The Biogas plantConsists of Aconcrete tank(10-15 feet deep) to collect bio-wastes and slurry of dung. A floating cover is placed over the slurry, which keeps on rising as the biogas is produced. Anoutletwhich is connected to a pipe to supply biogas. Anoutletto remove spent slurry (used as fertilizer).Indian Agricultural Research Institute (IARI)andKhadi and Village Industries Commission (KVIC):Developed technology of biogas production in India.MICROBES AS BIOCONTROL AGENTS-Biocontrol:It is the use of biological methods for controlling plant diseases and pests.-Chemical pesticidesandinsecticidesare harmful to all organisms and causes pollution. Chemical pesticide kills both useful and harmful life forms.Microbial biocontrol agentsoBacillus thuringiensis (Bt):to control butterfly caterpillar.These are available in sachets as dried spores which are mixed with water and sprayed on to vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed.The scientists have introducedB. thuringiensistoxin genes into plants. E.g. Bt cotton.oTrichoderma sp(fungus): are free livings that are seen in the root ecosystems. They are effective biocontrol agents of several plant pathogens.oBaculoviruses(Especially genusNucleopolyhedro-virus):Attacks insects and other arthropods.These are suitable forspecies-specific, narrow spectrum insecticidal applications. This is desirable in IPM program to conserve beneficial insects.MICROBES AS BIOFERTILISERS Biofertilisersare organisms that enrich nutrient quality of the soil. E.g. Bacteria, fungi, cyanobacteria etc. Rhizobium(symbiotic bacteria inroot nodules ofleguminous plants)fix atmospheric N2. Free-livings in the soil (E.g.AzospirillumandAzotobacter)enrich the nitrogen content of the soil. Mycorrhiza:Symbiotic association of fungi (E.g. the genus ofGlomus) with plants. The fungus gets food from the plant. The fungal symbiontoAbsorb phosphorous from soil and passes it to the plant.oGive resistance to root-borne pathogens and tolerance to salinity and draught.oGive an overall increase in plant growth and development. Cyanobacteria (Blue green algae):Autotrophic microbes. They can fix atmospheric nitrogen. E.g.Anabaena, Nostoc, Oscillatoria etc. In paddy fields, Cyanobacteria serve as an important biofertilisers. It also adds organic matter to the soil and increases its fertility.