·         Microbes are diverse – protozoa, bacteria, fungi and microscopic plants viruses, viroids and also prions (proteinocious infectious agents)

·         Microbes like bacteria and fungi can be grown in nutrient media to form colonies and can be seen in naked eyes.

·         Some microbes’ causes diseases and some are useful for human being.


        Lactic acid Bacteria:

·         Lactic acid Bacteria (LAB) grow in milk and convert it to curd.

·         LAB produces acids that coagulate and partially digest milk proteins.

·         A small amount of curd added to fresh milk as inoculums or starter.

·         LAB improves nutritional quality of milk by increasing vitamin B12

·         LAB plays very important role in checking disease causing microbes.

·         Dough, used to make dosa and idli is also fermented by bacteria.

·         The puffed-up appearance of dough is due to the production of CO2.

·         Baker’s yeast (Saccharomyces cervisiae) is used to making bread.

·         ‘Toddy’ a traditional drink is made by fermentation of sap from palms.

·         Large holes in ‘Swiss cheese’ are due to production of large amount of CO2 by a bacterium named Propionibacterium sharmanii.

·         The ‘Roquefort cheese’ is ripened by specific fungi, which gives specific flavor.


·         Microbes are used in industry to synthesize a number of products

·         Beverages and antibiotics are some examples.

·         Microbes are grown in very large vessels called fomenters.

Fermented Beverages:

·         Yeasts are used for production of beverages like wine, beer, whisky, brandy or rum.

·         Saccharomyces cervisiae commonly called ‘brewer’s yeast used for fermenting malted cereals and fruit juices to produce ethanol.

·         The type of raw material used for fermentation and the processing, different types of alcoholic drinks are produced.

·         Wine and beer are produced without distillation.

·         Whisky, brandy and rum are produced by distillation of the fermented brooth.


·         Antibiotics are the chemical substances which are produced by some microbes and can kill or retard the growth of other microbes.

·         The first antibiotic discovered is the penicillin, from a mould (fungus) Penicillium notatum.

·         Antibiotics have greatly improved our capacity to treat deadly diseases such as plague, whooping cough. Diphtheria and leprosy.

Chemicals, Enzymes and other Bioactive Molecules:

·         Aspegillus niger (a fungus) produces citric acid.

·         Acetobacter aceti (a bacterium) produce acetic acid.

·         Clostridium butylicum (a bacterium) produce butyric acid.

·         Lactobacillus (a bacterium) produces lactic acid.

·         Saccharomyces cerevisiae (yeast) used for production of ethanol.

·         Lipases are used in detergent produced by microbes.

·         Pectinase, proteases and cellulase, make bottled fruit juices clearer.

·         Streptokinase produced by Streptococcus used as a ‘clot buster’, for removing clots from the blood vessels.

·         Cyclosporin-A produced by a fungus called Trichoderma polysporum used as immunosuppressive agent in organ transplantation.

·         Statins produced by Monascus purpureus used as blood cholesterol lowering agents. It acts as competitive inhibitor for the enzyme responsible for synthesis of cholesterol.


·         The waste water generated in cities and town containing human excreta. This municipal water-water is called sewage.

·         Before disposal to the natural body sewage is treated in sewage treatment plants (STPs) to make it less polluting.

·         Treatment is done by heterotrophic microbes naturally present in sewage.

Primary treatment:

·         Involves the physical removal of particles – large and small from sewage through filtration and sedimentation.

·         Initially floating debris is removed by sequential filtration.

·         The grit (soil and small pebbles) are removed by sedimentation.

·         All solids that settle form the primary sludge, and the supernatant forms the effluents.

·         The effluents are from the primary settling tank taken for secondary treatment.


Secondary treatment or Biological treatment:

·         The primary effluent is passed into large aeration tanks.

·         This allows vigorous growth of useful aerobic microbes into flocs.

·         The growth of microbes consumes the major part of the organic matter in the effluent. This significantly reduces the BOD (biochemical oxygen demand) of the effluent.

·         BOD refers to the amount of oxygen required to oxidize total organic matter by bacteria, present in one liter of water.

·         BOD is the measures of the organic matter present in the water.

·         Greater the BOD of the waste water more is its polluting potential.

·         Once the BOD of sewage reduced significantly, the effluent is then passed into the settling tank where the bacterial ’flocs’ are allowed to sediment. This sediment is called activated sludge.

·         Small part of activated sludge is pumped back to aeration tank to serve as the inoculums.

·         The remaining sludge is pumped into anaerobic sludge digester.

·         In the anaerobic sludge digester there is other kinds of bacteria which grow anaerobically, digest the bacteria and fungi in the sludge.

·         During this digestion bacteria produce biogas, (mixture of methane, hydrogen sulphide and carbon dioxide)

·         The effluent from the secondary treatment plant is released into natural water body like rivers and streams.

·         Ganga Action Plan and Yamuna Action Plan initiated by Ministry of Environment and Forest to save these major rivers of our country.

·         It is proposed to build a large number of sewage treatment plants so that only treated sewage may be discharged into the rivers.


·         Biogas is a mixture of gases (predominantly methane) produced by the microbial activity and is used as fuel.

·         Certain bacteria grow anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2S. These bacteria are collectively called methanogens. One common bacterium is Methanobacterium.

·         These bacteria present in the rumen of cattle, plays essential role in nutrition of cattle by digesting cellulose. Hence the excreta (dung) used for the production of biogas.


·         Biocontrol refers to the use of biological methods for controlling plant diseases and pests.

·         Effect of use of chemical, insecticide and pesticide to control disease and pests:

o    These chemicals are toxic and extremely harmful to human beings and animals

o    Polluting our environment (soil, ground water), fruits, and vegetables.

o    Soil is polluted through use of weedicides to remove weeds.

Biological control of pest and disease:

·         Use of biocontrol measures will greatly reduce our dependence on toxic chemical and pesticides.

·         The Ladybird and Dragonflies are used to get rid of aphids and mosquitoes.

·         Bacillus thuringiensis (Bt) used to control butterfly caterpillars.

·         Dried spores are mixed with water and sprayed onto vulnerable plants, where these are eaten by the insect larvae.

·         In the gut of the larvae, the toxin is released and the larvae get killed.

·         Trichodermaa free living fungus used to control several plant pathogens.

·         Baculoviruses are pathogen that attack insects and other arthropods

·         The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus.

·         These viruses are excellent candidates for species-specific, narrow spectrum insecticidal application.

·         They have no negative impacts on plants, mammals, birds, fish, etc.

·         This is very use full in integrated pest managements (IPM).


·         Biofertilizers are organisms that enrich the nutrient quality of the soil.

·         Main biofertilizers are the bacteria, fungi and cyanobacteria.

·         Rhizobium form root nodules in legumes and fix atmospheric nitrogen.

·         Azospirilium and Azotobacter free living bacteria fix atmospheric nitrogen and thus increasing nitrogen content of the soil.

·         Mycorrhiza: fungi symbiotically associated with root of plants.

·         Many members of the genus Glomus form Mycorrhiza.

o    Provide phosphorus to the plants from the soil.

o    Make the plant resistant to root-borne pathogen.

o    Increase tolerance to salinity and drought.

·         Cyanobacteria like Anabaena, Nostoc, and Oscillatoria etc:

o    Fix atmospheric nitrogen.

o    add organic matter to the soil and

o    Increase soil fertility.


§  DO :        Dissolved  Oxygen

§  GAP :      Ganga  Action  Plan

§  KVIC :     Khadi  and  Village  Industries  Commission

§  TMV :      Tobacco  Mosaic  Virus

§  YAP :      Yamuna  Action  Plan

§  IPM:        Integrated Pest Management.

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