By going through these CBSE Class 12 Biology Notes Chapter 10 Microbes in Human Welfare, students can recall all the concepts quickly.

Microbes in Human Welfare Notes Class 12 Biology Chapter 10

→ Microorganisms are present everywhere in soil, air, and water and inside plant and animal bodies. They can withstand severe climatic conditions like very high (100°C) or very low (~50°C) temperatures, high acidic (pH2) conditions, etc. These may be bacteria, viruses, fungi, cyanobacteria, bacteriophages, viroids, and prions.

→ In the middle of the nineteenth century, Louis Pasteur observed that alcoholic fermentation of sugar required the multiplication of yeast cells.

→ Fermentation is the oldest microbial process.
It is of two types:

  1. Batch process and
  2. Continuous process.

→ An antibiotic is an organic compound produced by a microorganism that inhibits or kills another microorganism.

→ Although there are around 7000 antibiotics, known to exist, only about 150 are marketed, 10 are produced on large scale and about 300 new antibiotics are discovered every year.

→ The most common antibiotics and their sources are – Penicillin (Penicillium Notatum), Poly mixin-B (Bacillus Polymixa), Neomycin (Streptomyces Fradiae), Erythromycin (Streptomyces Erythraens), Chloramphenicol (Streptomyces Venezuela).

→ Vitamins are essential dietary factors that are required by us in small amounts. Out of all vitamins produced during the normal metabolism of microorganisms only two viz. Vitamin Bp and Vitamin B, are manufactured biotechnologically.

→ The important organic acids produced on a commercial scale by using microorganisms are acetic acid, citric acid, lactic acid, fumaric acid, gluconic acid, itaconic acid, kojic acid, butyric acid, and gibberellic acids.

→ Many microorganisms are known to transform naturally occurring steroids. These modified steroids have much medicinal importance.

→ By using recombinant DNA technology insulin is being produced using micro-organisms, which is similar to human insulin and is called humulin.

→ Streptokinase from streptococcus bacterium acts like a clot buster. It is helpful for patients who have undergone myocardial infarction.

→ Cyclosporin: A from the fungus Trichoderma polypore is used as an immunosuppressive agent and useful in organ transplantation.

→ Statins from yeast Monascus purpose is a blood cholesterol-lowering agent.

→ The municipal wastewater is called sewage. It contains large amounts of organic matter and many pathogenic microbes. In sewage treatment plants the treatment of wastewater is done by the heterotrophic microbes present in sewage.

→ Sewage treatment takes place in two main steps:

  1. primary treatment and
  2. secondary treatment.

In some advanced sewage treatment plants, it also undergoes tertiary treatment.

→ Primary treatment is done to remove large objects from the sewage. Sewage is passed through 2-8 cm apart steel bars, then through the wire mesh of reducing pores. It is passed through the grit chamber and then through the settling tank where most suspended material settles down as sludge.

→ The effluent flows for secondary treatment. First, the effluent is passed into aeration tanks where it continuously agitated and allows microbial growth. The microbes consume the organic matter and decrease the biological oxygen demand (BOD) of the effluent. It then passes to the settling tank where the sediment is called activated sludge.

It is passed to anaerobic sludge digesters where the anaerobic bacteria digest it further and produce gases like methane, H2S, and CO2. This is called biogas and can be used as fuel. The effluent may undergo tertiary treatment or released into natural water bodies.

→ Methanogens are bacteria that grow anaerobically on cellulose-rich materials and produce a large amount of methane gas with CO2 and H2. It is called biogas and is used as fuel. Methanogens are found in anaerobic sludge and also in cattle rumen where they come out in dung, so dung (rich in cellulose) can be used to generate biogas.
Microbes in Human Welfare 12 Notes Biology 1
Biogas plant

→ Biofertilizers are the microorganisms that enrich the soil with nutrients and maximize the ecological benefits and minimize environmental hazards. These include nitrogen-fixing bacteria, cyanobacteria, and fungi.

→ Manures are partially decomposed organic materials added to the soil to increase fertility of the soil.
These are of three types:

  1. farm-yard manure,
  2. compost, and
  3. green manure.

→ The disadvantages of chemical fertilizers and pesticides can be overcome by the use of alternative harmless manures, biofertilizers, biological control methods, and biopesticides.

→ The various types of biofertilizers are:

  1. Microphones bio fertilisers,
  2. Free-living nitrogen-fixing bacteria like Azotobacter,
  3. Symbiotic nitrogen-fixing bacteria forming an association with legumes like Rhizobium,
  4. A loose association of nitrogen-fixing bacteria like Azospirillum,
  5. Cyanobacterial biofertilizers and
  6. Azolla-Anabaena symbiosis.

→ Mycorrhizae are the symbiotic association of fungi with the roots of higher plants. These may be ectomycorrhizae and endomycorrhizal.

→ The ectomycorrhiza is characterized by the formation of a sheath or mantle on the surface of roots. They help in the absorption of water, absorption of inorganic nutrients, and protection of plants from pathogen attack.

→ The endomycorrhiza does not form an external sheath or mantle. The fungi mycelium penetrates into the roots and lives in the intercellular spaces as well as intracellularly in the cortical cells. Some endomycorrhizal are called vesicular-arbuscular mycorrhizae (VAM). They develop vesicles and arbuscules within the cells of the root. These fungi stimulate the absorption of phosphorus, zinc, copper, sulfur, potassium, and various other elements by the roots.

→ Biopesticides are pesticides of biological origin or biological control agents which are used to control weeds and pests.
They are two main types

  1. Bioherbicides and
  2. Bioinsecticides.

→ Bioherbicides or biological control of weeds involve the utilization of biological agents (such as insects, fungi, bacteria, nematodes, parasitic plants, etc.) which suppress or kill the weedy plants without causing significant injuries to other plants.

→ Bioinsecticides or the control of harmful insects by biological methods include

  1. The use of pathogens, parasites, and predators;
  2. Sterilization strategy;
  3. Use of insect hormones; and
  4. Use of natural insecticides.

→ Antibiotic: An antibiotic is a substance produced by a microorganism that inhibits the growth of other microorganisms.

→ Bioreactor: The fermentation tank where fermentation is carried out in the presence of micro-organisms.

→ Broad-spectrum antibiotics: The antibiotics which have the ability to act on several pathogenic species differing from each other in structure and composition of the cell wall.

→ Biological control: introduction of living organism which destroys other harmful organisms.

→ Chemical control: Use of chemical substances such as smoke, gas, dust, and sprays to poison pests.

→ Fermentation: The anaerobic oxidation of food in the presence of micro ‘organisms which result in the production of alcohol and waste ga CO2.

→ Fertilizer: Substance added to soil to increase the yield of crop plants.

→ Fungicide: Substances used for killing fungi.

→ Farmyard manure: The manure consisting of a mixture of cattle dung a4id crop residue.

→ Legume: The plants of the pea family i.e. Luguminosae e.g. pea plant beans etc.

→ Manure: The substances which are added to soil to increase crop yield.