Usage of Microorganisms, Microorganisms in Sewage Treatment, Vaccination and Microorganisms in Agriculture- Biology Guide for Class 8

Information about Usage of Microorganisms


Usage of Microorganisms, Microorganisms in Sewage Treatment, Vaccination and Microorganisms in Agriculture


Class 8


Class 8 Biology

Topics Covered

  • Uses in Food
  • Sewage Treatment
  • Microorganisms in Agriculture
  • Use in Energy/Fuel Production
  • Cleaning the Environment

Microorganisms are friendly to us in many ways.

Uses in Food

  • Curd and cheese formation
    Lactobacillus is a bacterium that helps in the formation of curd. At favourable temperatures, it multiplies in milk and converts it into curd. Some bacteria and fungi are also involved in the making of cheese. 
  • Fermentation process in bakery
    Fungi, like yeast, reproduce rapidly and produce carbon dioxide. This gas, when trapped in dough, or batter (used for idlies, dosas), causes it to increase in volume and makes it fluffy and soft. This is known as fermentation.
  • Alcoholic beverages
    Many microorganisms are used in the manufacture of alcohol, wine and acetic acid. Fungi, like yeast, convert natural sugars, present in cereals and fruits, into alcohol; this alcohol is then used to make alcoholic beverages. Acetic acid, commonly known as vinegar, is also produced by a similar process. 
Most microorganisms exhibit maximum growth in the temperature range 30°C-45°C. It is for this reason that we store perishable materials in the refrigerator.

Sewage Treatment

Some bacteria are used in the biological treatment of sewage and industrial waste, called effluent. This process is known as bioaugmentation.

Importance in Human Health

  1. Many microorganisms, present in the alimentary canal of some animals (like cows), help in digestion and absorption of food. The bacteria, present in our large intestine, help in bowel movement.
  2. Microorganisms are also used in production of antibiotics. Antibiotics are chemicals that inhibit the growth of (other) harmful microorganisms by affecting their life processes.
    For example, penicillin is an antibiotic obtained from a fungus, Penicillium notatum. Streptomycin, tetracycline and erythromycin are some antibiotics obtained from fungi and bacteria.
    • Antibiotics are extremely effective in treatment of various microbial infections/diseases, like, tuberculosis, cholera, etc.
    • However, antibiotics should be taken only on the advice of a qualified doctor and that too only in the prescribed dosage and for the prescribed duration.
    • Not completing the prescribed course may make them ineffective when used in future. If they are taken when not really required, they may kill some of the useful bacteria in the body. 
  3. When microorganisms, like bacteria or viruses, enter our body, they are recognised by special kind of blood cells.
    • These cells get stimulated to produce antibodies. Antibodies identify and destroy such disease causing organisms.
    • During this process the body 'remembers' the type of microorganisms; if the same microorganism enters the body again, it gets recognised and destroyed much faster. This is called 'immunity'.
    Immunity is, therefore, the natural ability of an organism to have an inbuilt mechanism to resist, and destroy, the infection that some microorganism may cause.

Immunity through Vaccination 

Vaccination is an important way to build immunity. A vaccine produces immunity to a disease by stimulating the production of antibodies. Vaccines are suspensions of killed, or weakened microorganisms (or products, or derivatives, of such microorganisms). The most common method of administering vaccines is by inoculation; however, some vaccines are given orally also.

Microorganisms in Agriculture

  • Some bacteria, and blue-green algae (cyanobacteria), are able to 'fix' (for use by plants) atmospheric nitrogen into usable forms of salts of nitrogen. They are called biological nitrogen fixers.
  • Rhizobium lives in symbiotic association in the root nodules of leguminous plants and enriches the soil with nitrogen compounds. Some cyanobacteria do the same in rice fields and in association with the roots of Cycas plant.

Use in Energy/Fuel Production

  • Many microorganisms produce ethanol by fermentation of sugars and produce methane in the biogas reactors. Both ethanol and methane are used as fuel for production of energy. 

Cleaning the Environment

  • When a plant or animal dies, it leaves behind nutrients and energy in the organic material that formed its body structure.
  • Decomposers eventually convert all such organic matter into carbon dioxide and nutrients. These nutrients (like nitrogen, phosphorous, magnesium, etc.) become a part of the soil.
  • This process eventually replenishes nutrients back to the ecosystem, thereby, allowing the plants to grow. Bacteria and fungi are some of the common decomposers.

Some other important points

  • Edward Jenner was an English doctor who pioneered the vaccination process. Jenner's discovery in 1796 — inoculation with cowpox gave immunity to smallpox — was an immense medical breakthrough and has saved countless lives. Smallpox has now been eradicated from the world. 
  • Probiotics (dietary supplements of live bacteria or yeasts) can help prevent, and treat diseases through a number of mechanisms. One way is by interacting directly with the disease-causing microbes making it harder for them to cause disease. An example of this is the ingestion of probiotic bacteria to prevent, or to treat, diarrhoea. These organisms help reinforce the natural bacterial barrier that exists on the lining of the digestive tract; they thus, provide additional protection against pathogenic organisms that can cause diarrhoea. 
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