Microbes in human welfare


  • Microbes are those living organisms which are microscopic i.e. can be seen only under a microscope.
  • Bacteria are omnipresent i.e. present everywhere in the soil, air, water, inside the body of animals and even in places where no other life forms can exist.
  • The diverse microbes are viruses, viroids, bacteria, fungi, protozoan and certain algae.
  • Microbes like bacteria and fungi can be cultured on nutritive media to form colonies in the laboratory.
Microbes are useful to mankind in many ways, while some are harmful too. The useful aspects are as follows:

Microbes in household products:

Curd is produced by Lactobacillus and other lactic and bacteria [LAB] which grow in milk and convert it into curd.
For example: Lactobacillus acidophilus, Streptococcus lactic.
Significance of LAB:
  • LAB produce acids that coagulate and partially digest the milk protein.
  • LAB also increases the nutritional quality of curd by increasing the content of vitamin B-12.
  • LAB plays an important role in checking disease causing microbes.

Yogurt production:
Streptococcus thermophilus and Lactobacillus bulgaricus.
Butter- milk production:
Streptococcus lactic, Leuconostoc citrovorum.
Dough formation:
The dough used for making bread is fermented by a fungi Saccharomyces cerevisiae [Baker’s yeast]
The dough used for making idli and dosa is fermented by bacteria, the puffed up appearance is due to the CO2 produced during fermentation.
Microbes are used to ferment fish, bamboo shoots and soybean to produce food- items.
Cheese production:
Cheese differ in texture, flavor and taste depending on the microbes used for fermentation or ripening.
  • Swiss cheese is ripened by bacterium Propionibacterium sharmanii which produces holes.
  • Roquefort cheese is ripened by specific fungus.

Microbes in Industrial products:

In industry, microbes are employed to produce
  1. Beverages
  2. Antibiotics
  3. Organic acids
  4. Enzymes
  5. Bioactive molecules, etc.
Industrial production requires the formation of large quantities of products which generally involves the microbial reaction to proceed in a specialized vessel called Fermentor or Bio-reactor.

  • Yeast (Saccharomyces cerevisiae i.e. Brewer's yeast) is used for fermenting fruit juices and malted cereals into ethanol.
  • Depending on the type of raw material used and the nature of processing, various alcoholic drinks are produced; eg with distillation- whisky, rum and brandy and without distillation wine and beer.

Antibiotics (against life):
Antibiotics are substances primarily produced by certain harmless micro- organisms which in low concentration are antagonistic to the growth of other micro- organisms such as pathogenic bacteria.
Penicillin is the first antibiotic to be discovered by Alexander Fleming, while working on Staphylococci bacteria but it’s potential as an effective antibiotic was established later by Ernest Chain and Howard Horey.
Penicillin is obtained from the fungus; Penicillium notatum.
Organic acids:
Organic acids
Citric acid
Aspergillus niger (fungus)
Acetic acid
Acetobacter aceti (bacterium)
Butyric acid
Clostridium botylicum
Lactic acid
Lactobacillus delbrueckii

The enzymes produced with the help of microbes are Lipases, Proteases and Pectinases.
Certain molecules produced by living organisms, perform certain functions in the body of other organisms and modify the metabolism hence, they are called Bioactive molecules.
They are those active compounds which are produced on commercial scale by the microbes and useful in the human welfare.
Cyclosporin A:
It is produced by the fungus Trichoderma polysporum and is used as an immune- suppressive agent during organ transplantation.

It is produced by the type of yeast Monascus purpureus. It is used to lower the level of blood cholesterol.

It is produced by the bacterium streptococcus. It function as a clot buster for removing the clots from the blood vessels of patients who have suffered myocardial infarction.

Microbes in Sewage Treatment:

  • The municipal wastewater (called sewage) contain large amount of organic matter and microbes.
  • The sewage is treated in sewage treatment plants before it is discharged into water bodies to reduce the pollution load.
  • The treatment involves 2 steps:
  1. primaryTreatment
  2. secondary Treatment
Primary Treatment:
  • It is a physical process of removal of small and large particles through filtration and sedimentation.
  • The first step is to remove floating objects like poly bags by letting the sewage to pass through wire mesh, screen of sequentially smaller pore size.
  • Then the sewage is allowed to passed into the grit chamber where grit is sedimented.
  • The sewage is allowed to go into the primary settler tank where the suspended material settled down to form the primary sludge.
  • The effluent is taken for secondary treatment.
Secondary Treatment:
  • It is a biological process that employs the Heterotrphic bacteria, naturally present in sewage.
  • The effluent from the primary treatment is passed into the large aeration tank, where it is constantly agitated and air is pumped into it.
  • This allows the rapid growth of aerobic microbes into ‘flocs’ which consume the organic matter in the sewage and reduce the BOD ( Biochemical Oxygen Demand).
  • When the BOD of sewage is reduced, significantly, the effluent is passed into a settling tank, where the flocs are allowed to sediment forming the activated sludge.
  • Small part of activated sludge is pumped back into the aeration tank as inoculum.
  • The remaining part of the sludge is pumped into an anaerobic sludge digester, , where  the Anaerobic bacteria and fungi digest the sludge, producing methane, H2S and CO2 i. e.,Biogas.

The effluent after secondary treatment is released into water bodies like streams. The programs like Yamuna Action Plan (YAP) and Ganga Action Plan (GAP) initiated by Ministry of Government and Forest depend upon sewage treatment before it is released into rivers.



  • Biogas, predominantly contains methane (60%) and remaining 40% is CO2.
  • Methanogens are commonly  involved in the production of biogas.
  • Methanogens like Methanobacterium and Methanococcus produce large quantities of methane along with CO2 and H2 gas by acting on cellulosic compounds.
  • They are found in the anaerobic sludge, rumen of cattle, flooded rice- field and marshy places. Cattle dung is used for production of biogas as it contain cellulosic material as well as methanogens.
  • The technology of biogas production was developed in India by Indian Agricultural Research Institute (IARI) and Khadi and Village Industries commission (KVIC).
The steps of biogas production are as follows:
  • The biogas plant consists of 10-15ft. deep concrete tank, in which the slurry of the dung is fed.
  • A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank by microbial activity.
  • The biogas plant has an outlet i.e., connected to a pipe, for removal of biogas and supply of it to a required place.
  • There is an outlet to remove the spend slurry which can be used as fertilizer.



Bio control agents refer to those organisms which are employed to control some harmful organisms like pathogenic organisms and pests of the plants.
  • Bio control refers to the use of biological methods for controlling plant disease and pest, these methods rely on natural predation rather than on the introduced chemicals.
  • An organic gardener works to create a system where pests/ insects are not eradicated but are kept at manageable levels by a complex system of check and balance within in the ecosystem.
  • The beneficial predatory and parasitic insects which depend upon these insects/pests are able to survive.
  • For Example: Ladybird, Beetle is useful to get rid of aphids and dragonflies, mosquitoes.
  • Bacillus thuringiensis is a bacterium whose spores are toxic to certain insect's larvae and kill them but not harmful to other insects.
  • The toxic producing genes of this bacterium are transferred into crop plants which become resistant to insect pests. For example: Bt Cotton.
  • Another biological control gene development for control for plant disease is a fungus, Trichoderma which is a free living in soil and root ecosystem and is effective against several plant pathogens.


Bio-fertilizers are organisms which can bring about soil nutrient enrichment. The sources of bio-fertilizers are :
Bacteria, Cyanobacteria and fungus.
Symbiotic bacteria—Rhizobium
Free-living bacteria—Azospirillum Azotobacter
Use : They fix the atmospheric nitrogen and enrich soil nutrients.
Anabaena, Nostoc, Oscillatoria etc.
Use: They function as bio- fertilizers by fixing atmospheric Nitrogen and increasing the organic matter of soil through their photosynthetic activities.
Fungi/ Mycorrhiza
Fungi forms symbiotic association with roots of higher plants known as Mycorrhiza)
For Eg. Glomus
Use: The fungus absorbs Phosphorus and passes it on to the plants.
Other benefits of mycorrhiza are:
  • Resistant to root- borne pathogens
  • Tolerance to salinity
  • Tolerance to drought
  • Overall increase in plant growth and development.

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