NCERT Solutions for Class 12 Science Biology Chapter 10 - Microbes In Human Welfare

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The conversion of milk into curd by lactic acid bacteria (LAB) improves its nutritional quality by increasing vitamin B₁₂.

Hence, the correct answer is option C.

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Sludge generated by the primary treatment of waste is pumped into large tanks called anaerobic sludge digesters. In this anaerobic bacteria grow anaerobically, digest the bacteria and the fungi in the sludge and during this digestion, the bacteria produces a mixture of gases such as methane, hydrogen sulphide and carbon dioxide.

Hence, the correct answer is option a.   

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Methanogenic bacteria are anaerobic bacteria and is not found in the activated sludge. In the activated sludge, the aerobic bacteria grow rapidly and form flocs.

Hence, the correct answer is option d.

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The primary treatment of waste water involves the physical removal of large and small particles from the sewage through filtration and sedimentation.

Hence, the correct answer is option b.

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Biochemical oxygen demand (BOD) is measured by the rate of uptake of oxygen by micro-organisms in a sample of water. It is the measure of the organic matter is present in the water.

Hence, the correct answer is option a.

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Wine and beer are produced without distillation of the fermented broth.

Hence, the correct answer is option a.

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The technology of bio-gas production was developed in India is due to the efforts of Indian Agricultural Research Institute (IARI) and khadi and village Industries commission (KVIC)

Hence, the correct answer is option c.

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Trichoderma is a fungus and act as a biological control agent used for the treatment of plant disease. These species are free-living fungi that are common in the root ecosystem.

Hence, the correct answer is option b.

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When the oxygen availability in the activated sludge floes is reduced, the floes will become anoxic results in the death of bacteria as they are aerobes and requires oxygen for their growth. This eventually causes the breakage of floes.

Hence, the correct answer is option b.

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Mycorrhiza  is the symbiotic association of fungi with plants. The fungal symbiont absorbs phosphorus from the soil and passes it to the plant. In turn, plants have such associations such as resistance to root-borne pathogens, tolerance to salinity and drought.

Hence, the correct answer is option d.

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Pseudomonas is a deniturifying bacteria involved in the denitrification or reduction of nitrates into nitrogen.

Hence, the correct answer is option d.

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The production of large holes in 'swiss cheese' are due to the formation of CO₂ by a bacterium Propionibacterium Shermanii.

Hence, the correct answer is option c.

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The residue left after methane productions from cattle dung is used as manure. As it supplies organic materials and minerals to the soil.

Hence, the correct answer is option c.

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Methanogens are anaerobic bacteria that produces methane, H₂S (hydrogen sulphide) and carbon dioxide.

Hence, the correct answer is option a.

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The activated sludge is a sediment that contains bacterial flocs. So, a small part of activated sludge is pumped back to into the aeration tank to serve as the inoculum.

Hence, the correct answer is option a.

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Correct Match
 

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The large holes in 'Swiss cheese' is due to the production of a large amount of carbon dioxide (CO₂) by a bacterium.
Puopionibacterium Sharmanii

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Fermentors are very large vessels required for the production of products on an industrial scale. For this, microbes are growing in such large vessels.

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Statin is a blood-cholesterol lowering agent produced by the yeast Monascus purpureus. It acts by competitively inhibiting the enzyme responsible for cholesterol synthesis.

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The secondary waste water treatment is also called biological treatment because it involves microbial action for digestion of waste.

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Necleopolyhydroviruses are excellent candidates for species specific, narrow spectrum insecticidal applications. They have no negative impacts on plants, mammals, birds, fish and on non-target insects.

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The discovery of antibiotics have have created a revolution in the treatment of of several diseases. As many infections are incurable earlier, but after the discovery, they can now be treated with antibiotic and helps in saving the life of many people.

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Distillation is required for the production of certain alcoholic drinks to increase the overall content of alcohol in those drinks.

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Aspergillus niger, Clostridium butylicum  and Lactobacillus all are microbes involved in the commercial and industrial production
of acids.
Aspergillus niger – (fungus) - citric acid Clostridium butylicum - (bacterium) - Butyric Lactobacillus - (Bacterium) - Lactic acid.

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If the intestine of humans have same microbial flora that is also found in the rhumen of cattle, then the digestive system of the humans have ability to digest cellulose and methane gas can be produced by the digestive system.

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(E.coli, Agrobacterium tumefaciens, and Bacillus thuringiensis are some microbes useful in the field of biotechnology.

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ECORI comes from Escherichia Coli Ry 13.
In ECORI, the letter 'R' is derived from the name of strain and roman numbers following the names indicate the order in which the enzymes were isolated from the strain of bacteria.

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Bt Cotton is a genetically modified crop produces an insecticide protein that makes the plant resistant cotton bollworms .

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Blue-green algae is not popular as bio-fertiliser because they are only grow in water and carry out the process of nitrogen fixation. Paddy is the only crop that grows in water. Blue-gueen algae supports the growth of paddy crop.

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Penicillium roqueforti is the species of Penicillium poroduces Roquefort cheese.

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Uttar Pradesh, Jharkhand, West Bengal, Uttarakhand and Bihar are the states involved in the Ganga action plan.

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Lipases are enzymes used in detergent formulations. They are helpful in removing oil stains from the laundry. Pectinases and proteases are used for the clarification of bottled fruit juices.

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Cyclosporin A is used as an immunosuppressive agent in organ transplant patients. It is produced by the fungus Trichoderma polysporum.

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An example of a rod-shaped virus is Tobacco Mosaic virus (TMV) that causes mosaic disease in tobacco leaves.

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Methanogens are the group of bacteria found in the rumen of cattle and sludge of the sewage treatment plant. They produce methane gas. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant.Plant have such symbiotic associations are resistance to root borne pathogens, tolerance to salinity, drought and an overall increase in the plant growth and development.

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Propionibacterium Shermanii is a bacterium used for the commercial production of 'Swiss cheese'.

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Flocs are the masses of bacteria associated with the fungal filaments to form a mesh like structures. They consume the maximum amount of the organic matter in the effluent and significantly reduces the Biochemical oxygen demand (BOD) of the effluent.

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Bacillus thuringiensis produces an endotoxin. which is ingested by the bacteria. Is It is then released into the gut of an insect and binds to the surface of mid-gut of epithelial cells. It create pores results in cell swelling and lysis and eventually cause death of the insects.

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Mycorrhiza  is the symbiotic association of fungi with plants.

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Cynobacteria (Anabaena, Nostoc, Oscillatoria) are autotrophic microbes that can fix atmospheric nitrogen. In paddy fields, they serve as an important biofertiliser. They also add organic matter to the soil and increases its fertility.

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Alexander fleming working on bacteria staphylococci and observed that a mould growing in one of his unwashed culture plates around which staphylococci could not grow.
Later, Fleming found out that, the growth of mould was due to a chemical produced by it and he named it Penicillin after the mould Penicillium notatum.

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Alexander fleming discovered Penicillin. While its effectiveness was establised later by Ernst Chain and Howard florey and they awarded for their discovery.

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Some bio-active molecules of fungal origin that help in restoring good health in humans are:
(i) Cyclosporine A is used as an immunosuppressive agent in organ transplant patients. It is produced by the fungus Trichoderma Polysporum.
(ii) Statins is a blood cholesterol lowering agent produced by the yeast Monascus purpureus. This acts by competitively inhibiting the enzyme responsible for cholesterol synthesis.
(iii) Penicillin is produced by the mould Penicillium notatum.

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Lipases are enzyme used for detergent formulations and are helpful in removing oily stains from the laundry. This enzyme is obtained from Bacillus sps and Pseudomonas sps.

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The chemical nature of biogas is methane, carbon dioxide and hydrogen sulphide. Methanogens are involved in biogas production.

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Chemicals released from fertilisers and pesticides are toxic to flora and fauna as well as human. These chemicals pollute the environment. Microbes can be used as bio-fertilisers and bio pesticides to reduce the environmental degradation caused by chemical. They enrich the soil nutrients and increases its fertility.

For example:- Rhizobium, Azotobacter, Azospirillium. They fix atmospheric nitrogen in the soil. Bacillus thuringensis is a bacteria acts as a bio-pesticide and to control the
growth of insects/pests. Trichoderma is used as an effective bio-control agent. Nucleopolyhedrovirus are excellent for species- specific, narrow spectrum insecticidal applications.

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Broad-spectrum antibiotics are those antibiotics that are effective against both gram-positive and gram-negative bacteria.

For example:- Tetracycline , Azithromycin, Chloramphenicol

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Bacteriophage are virus that attack bacteria. These virus enters a bacterial cell and use bacterial genetic material as its own to produce more viruses through lytic or lysogenic cycles.

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Streptokinase is produced by the bacterium Streptococcus. This is genetically modified to used as a 'clot buster' for removal of blood clots from the blood vessels of patients who have undergone myocardial infarction results to heart attack.

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Biofertilisers are organisms that enrich the quality of nutrient in the soil. Their main sources are bacteria, fungi and cyanobacteria.
For example :- Rhizobium is the symbiotic association with the root nodules of the leguminous plants. Azospirillum and Azotobacter are free - living bacteria than can fix-nitrogen and increases the nitrogen content of the soil.

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With the help of aerobic degradation of waste water, a large part of the organic sludge is digested. It helps to reduce the BOD of the sewage water and make it fit for aquatic organisms. Activated sludge is produced after aerobic degradation. It liberates gases such as carbon dioxide and methane. These are main constituents of the biogass. The de-composers along with the organic matter are get separated and are rich in nutrients.
In this way, the aerobic degradation more important than anaerobic degradation for the treatment of large volume of waste water.

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(a) Before the year 1985, only some cities and towns had sewage treatment plants. So, most of the water from the urban as well as rural areas was discharged directly into river and pollute them. The ministry of environment and forests has initiated development of sewage treatment plants under the control of National River Conservation Authority. Ganga Action Plan (GAP) and Yamuna Action Plan in order to save these rivers from pollution. The government of India has named the Ganga Action Plan as Namami Gange.

(b) The Ganga river is the largest river in India that covers a total distance of 2520 km approximately across India and Bangladesh. This rivers provides the habitat for many plant and
animal species. The Gangetic Plain also also supports the livelihood of billions of people. High level of pollution effects the life of organism in river Ganga.

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The use of biocontrol agents for controlling pests is a natural and eco-friendly method. It involves the use of organisms to control pest and pathogens in the ecosystem.

For example: - Trichoderma species is a free living fungi and are effective biocontrol agents for several plant pathogens.
Bacillus thuringenesis acts as a biopesticide to control the insects that effects the yield of cotton plants.
Baculoviruses belongs to genus nucleopolyhedrovirus are used as biological control agents.
These viruses are effective for species-specific narrow spectrum insecticidal applications.

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(a) If a large volume of untreated sewage is discharged in a river.

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Lactobacillus and other bacteria are commonly called Lactic and bacteria (LAB). They grow in milk and facilitates the conversion of milk into curd.
They produce acid that coagulate and partially digests the milk protein. LAB also improves the nutritional quality of curd by increasing vitamin B₁₂ content. LAB play a very important role in checking disease causing microbes in the stomach.