Chapter 8: Microbes in Human Welfare

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A sample, Curd, can be used for the study of microbes. Numerous lactic acid bacteria (LAB) or Lactobacillus are present in Curd. Acids are produced by these bacteria that coagulate and digest milk proteins.

In the research laboratory, a tiny low drop of curd is carried because it contains multitudes of bacteria, which might be easily observed under a microscope which are of varied shapes and sizes.

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For the release of gases during metabolism, the examples are:

(a) A puffed appearance is seen in dough which is used for making idli and dosa . This is Due to the action of bacteria; carbon dioxide is released. This CO₂ released from the dough gets caught within the dough, hence giving it a puffed appearance.

(b) During wastewater treatment, the digestion of sludge produces a bacteria which is a mixture of gases such as methane, hydrogen sulphide and carbon dioxide.

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Lactic acid bacteria is present in curd.

Their useful applications are as follows:

(i) Formation of milk into curd is produced by this bacterium.

(ii) Multiplication of the bacterium increases its number, which converts the milk into curd. 

(iii) The content of vitamin B12 increases in the curd.

(iv) Presence of lactic acid bacteria in the stomach keeps a check on the disease- causing micro-organisms.

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(i) In the making dosa and idli, rice powder is fermented by bacteria and for creating bread (from wheat), yeast (Saccharomyces cerevisiae) is employed.

(ii) Gutta (made from black gram) also uses bacteria.

(iii) Microbes are accustomed to ferment fish, soya bean and bamboo shoots to create foods.

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(i) Several microorganisms are used for preparing medicines. In order to kill other disease-causing microorganisms antibiotics were developed which are produced by certain microorganisms.

(ii) Medicines are usually obtained from bacteria and fungi. Either they get killed or the growth gets stopped by disease-causing microorganisms.

(iii) For the treatment of life-threatening diseases such as plague, whooping cough (kali khansi), diphtheria (galghotu) and leprosy (kusht rog) and for many other common infections different antibiotics were used which are Streptomycin, tetracycline, and penicillin are common ones .

(iv) Growth of Staphylococci bacteria in the body was checked by chemical penicillin produced by Penicillium notatum, a fungus.

(v) Bacteria were destroyed by weakening their cell walls by antibiotics. Due to this weakening, certain immune cells such as the white blood cells enter the bacterial cell and cause cell lysis. The process of destroying cells such as blood cells and bacteria is cell lysis.

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Antibiotics are drugs produced by certain microorganisms to fight disease-causing microorganisms. These medications are frequently derived from microbes and fungus.

The following fungi are used in the production of antibiotics.

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The municipal waste matter is the sewage which is carried away in sewers and drains.

It consists of both liquid and solid wastes, which is rich in organic matter and microbes. Most of these microbes are pathogenic and may cause several water- borne diseases. Sewage water is a major source of polluting drinking water. Hence, it is important that sewage water should be properly collected, treated, then disposed of.

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Yes, microbes can be used as an energy source. Bacteria like Methane bacterium are employed for the generation of gobar gas or biogas.

(i) In a biogas plant, the generation of biogas is an anaerobic process which consists of a concrete tank (10-15 feet deep) with sufficient outlets and inlets.

(ii) Slurry is formed by the mixture of dung and water and is further thrown into the tank. The digester of the tank contains numerous anaerobic methane-producing bacteria, which produce biogas from the slurry.

(iii) Biogas can be used as a source of energy after removal through the pipe, while the spent slurry is removed from the outlet and is used as a fertilizer.

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Organisms that enrich the nutrient quality of the soil are the microbes which can be employed as biofertilizers .Bacteria, fungi and cyanobacteria are the main sources of biofertilizers . By this, fertility of the soil is increased in many ways

(i) Nodules on the roots of leguminous plants (a symbiotic association) that is formed by Rhizobium fixes the atmospheric nitrogen into organic form, which is used by the plant as a nutrient.

(ii) Fixing atmospheric nitrogen by Azospirillum and Azotobacter , while living freely, and enhancing the nitrogen content of the soil.

(iii) Symbiotic association is formed by the many members of the genus Glomus (fungi) with vascular host plants known as mycorrhiza that:

1. Helps within the absorption of phosphorus from soil and pass it to the plant.

2. Resistance to root-borne pathogens are developed within the plants.

3. Overall increase in plant growth and development can be done by increasing their tolerance to salinity and drought.

(iv) Cyanobacteria autotrophic microbes, e.g., Anabaena, Nostoc, Oscillatoria can fix atmospheric nitrogen, in aquatic and terrestrial environments and also add organic matter to the soil and increase its fertility.