NEET Biology Class 12 Microbes In Human Welfare Notes

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Microbes In Human Welfare

Several microbes such as bacteria, viruses, fungi, etc. are useful to man in many ways. Some of them are given below:

Microbes In Household Products

Lactobacillus or Lactic acid bacteria (LAB):

  • It converts milk curd by producing acids that coagulate and partially digest the milk proteins.
  • Fresh milk can be converted to curd by adding some curd containing LAB. It also increases vitamin B12 in curd.
  • In the stomach, LAB helps to check pathogens.

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Bacterial fermentation (anaerobic respiration):

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  • In dough is used to make foods such as dosa, idle, etc.
  • The puffed-up appearance of dough is due to the production of CO2.

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Baker’s Yeast (Saccharomyces Cervidae):

  • It is used to make bread by fermenting dough.
  • Toddy is made by fermenting sap from palms.
  • Microbes are used to ferment fish, soya beans & bamboo shoots and to produce cheeses.
  • Swiss cheese has large holes due to the production of CO2 by
  • Propionibacterium sharmanii (a bacterium).

Roquefort cheese is ripened by growing a fungus on it.

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Microbes In Industrial Products

Microbes In Industrial Products: Production of beverages, antibiotics, etc. on an industrial scale, requires growing microbes in very large vessels (fermenters).

Fermented beverages:

  • Saccharomyces cerevisiae (Brewer’s yeast) is used in the production of beverages by fermenting malted cereals and fruit juices to produce ethanol.
  • Wine and beer are produced without distillation.
  • Whisky, Brandy, Rum, Gin, Arrack, etc. are produced by distillation of fermented broth.

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Antibiotics:

  • Chemical substances produced by some microbes can kill or retard the growth of pathogens.
  • They are used to treating plague, whooping cough, diphtheria, leprosy, etc.
  • Penicillin: The first antibiotic discovered by Alexander
  • Fleming:  He observed that Staphylococci could not grow around a mold (Penicillium nota tum) growing in unwashed culture plates. He extracted penicillin from it.
  • Earnest Chain and Howard Florey established its full potential as an effective antibiotic.
  • Fleming, Chain & Florey were awarded the Nobel Prize (1945).

Chemicals, enzymes & other bioactive molecules:

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1. Organic acids: Acid-producer microbes include

  • Aspergillus Niger (a fungus): Citric acid
  • Acetobacter aceti (a bacterium): Acetic acid
  • Clostridium bretylium (a bacterium): Butyric acid
  • Lactobacillus (a bacterium): Lactic acid

2. Alcohol: Yeast (S. Cervidae) 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 by Streptococcus. Used as a ‘clot buster’ to remove clots from the blood vessels of patients who have myocardial infarction.

4. Cyclosporine A: Produced by Trichoderma polysporum (fungus). Used as an immunosuppressive agent in organ transplant patients.

5. Statins: Produced by Monascus purpure us (a yeast). Used as blood-cholesterol-lowering agents. It inhibits the enzymes responsible for the synthesis of cholesterol.

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Microbes In Sewage Treatment

Microbes In Sewage Treatment: Sewage (municipal wastewater) contains large amounts of organic matter and microbes. Sewage is treated in Sewage Treatment Plants (STPs) to make it less polluting.

It includes 2 stages:

  1. Primary treatment:
    • It is the physical removal of particles. It includes
    • Removal of floating debris by sequential filtration.
    • Removal of the grit (soil & pebbles) by sedimentation.
    • The settled solids form the primary sludge and the supernatant forms the primary effluent.
  2. Secondary treatment (Biological treatment):
    • Primary effluent is passed into large aeration tanks and constantly agitated. This allows vigorous growth of useful aerobic microbes into a flock (bacteria associated with fungal filaments form mesh-like structures).
    • These microbes consume the organic matter in the effluent. This reduces the BOD (Biochemical Oxygen Demand) of the effluent.

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BOD:

The amount of O2 consumed by bacteria to oxidize all organic matter in one liter 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 bacterial ‘flocs’ are sediment. This sediment is called ‘activated sludge’.

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A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum.

  • The remaining sludge is pumped into large tanks called anaerobic 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 is released in natural water bodies like rivers and streams.
  • The Ministry of Environment & Forests has initiated the Ganga Action Plan & Yamuna Action Plan to save water

Microbes In The Production Of Biogas

Microbes In The Production Of Biogas:

  • Biogas: Biogas is a mixture of gases (mainly CH4) produced by microbial activity. It is used for cooking & lighting.
  • Methanogens: Methanogens grow anaerobically on cellulosic material and produce CH4, for example, Methanobacterium.
  • Methanobacterium: Methanobacterium is found in the anaerobic sludge and rumen of cattle (for cellulose digestion).
  • The dung of cattle (gobar) is rich in these bacteria. Dung can be used for the generation of biogas (Go bar gas).
  • The Biogas plant consists of A concrete tank (10–15 feet deep) that collects bio-waste and a slurry of dung.
  • A floating cover is placed over the slurry, which keeps on rising as the biogas is produced.
  • An outlet that is connected to a pipe supplies biogas.
  • An outlet to remove spent slurry (used as fertilizer).

Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC): Developed technology for biogas production in India.

Microbes In Human Welfare Class 12 Notes

Microbes As Biocontrol Agents

Microbes Biocontrol Agents:

  1. Biocontrol: Biocontrol is the use of biological methods for controlling plant diseases and pests.
  2. Chemical pesticides: Chemical pesticides and insecticides kill both useful and harmful organisms and cause pollution.

Microbial biocontrol agents:

Bacillus do huringiensis (Bt): To control butterfly caterpillar.

  • The dried spores of Bt (available in sachets) are mixed with water and sprayed on vulnerable plants such as brassicas and fruit trees. These are eaten by the caterpillar. In their gut, the toxin is released, and the larvae get killed.
  • Scientists have introduced B. the huringiensis toxin genes in implants. For example, Bt cotton.

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Trichoderma sp (fungus): These are free living present in the root ecosystems. They control several plant pathogens.

Microbes In Human Welfare Class 12 Notes

Baculoviruses (Especially genus Nucleopolyhedrovirus):

  • Attacks insects and other arthropods.
  • These are suitable for species-specific, narrow-spectrum
  • insecticidal applications. This is desirable in IPM (Integrated
  • Pest Management) program to conserve beneficial insects.

Microbes As Biofertilizers

Microbes Biofertilizers:

Class 12 Microbes In Human Welfare Notes

Biofertilizers: Biofertilizers are organisms that enrich the nutrient quality of the soil for example, Bacteria, fungi, cyanobacteria, etc.

Rhizobium: Rhizobium (symbiotic bacteria in root nodules of leguminous plants) fix atmospheric N2.

  • Free-living bacteria in the soil (for example, Spirillum and
  • Acetobacter) enrich the nitrogen content of the soil.
  • Mycorrhiza: Symbiotic association of fungi (For example, genus of Glomus) with plants.
  • The fungus gets food from plants.
  • The fungal symbiont performs the following:
  • Absorb phosphorous from the soil and pass it to the plant.
  • Give resistance to root-borne pathogens and tolerance to salinity and drought.
  • Give overall increase in plant growth and development.

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Cyanobacteria (Blue-green algae): Autotrophic microbes.

  • They fix atmospheric nitrogen. For example, Anabela, Nostoc,
  • Oscillatoria etc. In paddy fields, Cyanobacteria serve as important biofertilizers.
  • It adds organic matter to the soil and increases its fertility.

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