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Q1. Explain in brief about the Yamuna Action Plan.

Solution

Most of the sewage water from urban as well as rural areas was discharged directly into the rivers resulting in their pollution. In order to protect the major rivers in India from sewage pollution, the Ministry of Environment and Forests has initiated development of sewage treatment plants under the National River Conservation Authority, e.g. Ganga Action Plan, Yamuna Action Plan etc. Under these plans, a large number of sewage treatment plants were built so that only treated sewage is discharged in the rivers. Importance of microbial treatment of sewage was then realized and more sewage treatment plants were established.

Q2. Name the group of organisms and the substrate they act on to produce biogas.

Solution

Name of the group of organisms-Methanogens Substrate-Cellulosic material/cow dung/agricultural waste

Q3. Which bacterium is involved in the production of Swiss cheese? What is its role?

Solution

The bacterium Propionibacterium sharmanii is involved in the production of Swiss cheese. It produces the characteristic texture with large holes due to CO₂ production, flavour and taste.

Q4. (a) Baculoviruses are excellent candidates for integrated pest management in an ecologically sensitive area. Explain giving two reasons. (b) What is organic farming? Why is it suggested to switch over to organic farming?

Solution

(a) Baculoviruses are excellent candidates for integrated pest management in an ecologically sensitive area because: (i) Baculoviruses are biological control agents. They are an excellent source for species-specific, narrow-spectrum insecticidal applications. (ii) They have no negative effect on plants, mammals or even on non-target insects.   (b) The use of biofertilisers and biopesticides to improve crop yields to minimise the problems associated with the overuse of chemical fertilisers is known as organic farming. It is advisable to switch to organic farming due to the following reasons: (i) Excessive use of chemical fertilisers makes the soil unfit for cultivation. (ii) Natural resources get depleted due to the production of chemical fertilisers.

Q5. Why should biological control of pests and pathogens be preferred over the conventional use of chemical pesticides? Explain how the following microbes act as biocontrol agents: (a) Bacillus thuringiensis (b) Nucleopolyhedrovirus

Solution

Biological control of pests and pathogens is preferred over the conventional use of chemical pesticides because: (i) The chemicals cause pollution of water bodies as well as groundwater. They also enter the plant body through the soil. (ii) The chemicals are extremely harmful to human beings and other animals.   Microbes as biocontrol agents: (a) Bacillus thuringiensis: Bt toxin genes when introduced into a plant, the plant becomes resistant to attack by insect pests. The protein toxins are available in the form of dried spores, which are mixed with water and sprayed onto the vulnerable plants. When these toxins are ingested by the insect larvae, they are released in the insect gut where they become active and kill the larvae. Specific Bt toxin genes obtained from B.thuringiensis are incorporated in several crop plants which make them resistant to insect pests. (b) Nucleopolyhedrovirus: These viruses are an excellent source for species-specific, narrow spectrum insecticidal applications. This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme.

Q6. (a) What are biopesticides? Give any two examples of their application. (b) What are mycorrhizae? How do they act as biofertilisers?

Solution

(a) Biopesticides are biological control agents and their products are used to control pests like weeds, insects and pathogens. Bioherbicides like Dalpon are used to control broad-leaved weeds of cereal crops and Baculoviruses are bioinsecticidal viral pathogens that kill insects and other arthropods. (b) The symbiotic association of fungi and roots of higher plants is called mycorrhiza. The fungal hyphae increase the absorptive surface of roots which facilitates better intake of nutrients such as nitrogen, phosphorus, calcium etc., assist in absorption of water, carry out solubilisation of complex organic molecules into simple inorganic nutrients, their absorption and transfer to roots, offer protection to the plants from the attack of disease-causing pathogens by secreting antimicrobial substances and provide tolerance to salinity and drought.  

Q7. List the characteristics of an ideal pesticide.

Solution

An ideal pesticide should possess the following characteristics: 1. It should be inexpensive and easily available. 2. It should be effective only against the specific target organism. 3. It should be non-persistent. 4. It should be non-toxic to other living organisms. 5. It should be biodegradable.

Q8. State any three properties of antibiotics.

Solution

Properties of antibiotics: (i) It should not kill the useful microbial flora found in the alimentary canal of man. (ii) It should not cause any harmful side-effects in the host. (iii) It should have quick action and should be broad spectrum, i.e., must have the ability to act on various pathogenic microorganisms which differ from each other in their structure and composition of cell wall.

Q9. Name a microbe used for statin production. How do statins lower blood cholesterol level?

Solution

Monascus purpureus is used for statin production. Statins lower blood cholesterol level by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.

Q10. Name the enzyme produced by Streptococcus bacterium. Explain its importance in medical sciences.

Solution

Streptococcus bacterium produces streptokinase. It is used for removing clots from the blood vessels of a patient suffering from myocardial infarction or in a heart patient.

Q11. What are the advantages of using biofertilisers in agriculture?

Solution

Advantages of using biofertilisers in agriculture: 1. They do not cause any form of environmental pollution. 2. They are inexpensive and economical. 3. At places where irrigation is not sufficient, few biofertilisers even improve the crop yield. 4. They enhance soil structure and function. 5. They increase the availability of vitamins and other growth promoting substances.

Q12. Explain the different steps involved in sewage treatment before it can be released into natural water bodies.

Solution

Municipal sewage treatment involves the following steps: 1. Primary treatment/Physical treatment: It involves the removal of large and small particles from sewage. The floating debris is first removed by sequential filtration through wire mesh screens. Then, soil and smaller particles are removed by sedimentation in the settling tank. The sediment is called primary sludge and the supernatant is called effluent. The effluent is then sent for secondary treatment. 2. Secondary treatment/Biological treatment: Primary effluent is passed through large aeration tanks with constant mechanical agitation and air supply. Useful aerobic microbes grow rapidly and form flocs. The growing microbes consume organic matter and thereby, reduce the BOD of the effluent. After this, the effluent is passed into the settling tank. The bacterial flocs settle down and the sediment is now called activated sludge. A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digestors. In the digestors, heterotrophic microbes anaerobically digest bacteria and fungi in the sludge producing a mixture of gases such as methane, hydrogen sulphide and CO₂ which form biogas.      

Q13. What are biopesticides? Give the scientific name and the use of first commercially used biopesticide in the world.

Solution

Biopesticides are biological control agents which are used to kill or control weeds and specific pests. Now-a-days, biopesticides are used in place of chemical fertilisers. Bacillus thuringiensis (Bt) is the first commercially used biopesticide in the world.

Q14. Name any three enzymes used in industry and state their significance.

Solution

Some important enzymes used in industry and their significance is as follows:   Enzyme Significance Protease Used in the leather industry in bating of hides, in textile industry for the removal of proteinaceous stains, in silk industry to liberate silk fibres etc. Streptokinase Used as a clot buster for the removal of clots from the blood vessels of a heart patient by dissolving the intravascular fibrin Amylase Used for the removal of starch from woven cloth, preparation of starch pastes for use in paper coating, clearing of turgidity in the manufacture of corn etc.    

Q15. What are biofertilisers? Give the significance of biofertilisers.

Solution

Biofertilisers are organisms that enrich the nutrient quality of soil. Significance of biofertilisers: 1. Increase the soil fertility 2. Reduce the use of chemical fertilisers and in turn, the chances of environmental pollution

Q16. How is the presence of cyanobacteria in paddy fields beneficial to the rice crop?

Solution

Cyanobacteria can fix atmospheric nitrogen. The soil conditions in paddy fields provide suitable environment for the growth of nitrogen fixing cyanobacteria. Cyanobacteria act as important biofertilisers. They also add organic matter to the soil and increase its fertility.

Q17. How do mycorrhizae act as biofertilisers? Explain. Name a genus of fungi that forms mycorrhizal association with plants.

Solution

Mycorrhiza is a symbiotic association of a fungus with the roots of higher plants. The fungus absorbs water and phosphates from the soil and passes it to the plant. It solubilises complex organic matter into simpler substances. It also provides resistance to root-borne pathogens and increases the tolerance of plant to salinity and drought. In this way, the mycorrhizae act as effective biofertilisers. The most common fungi that form mycorrhizal association with plants are Glomus species.

Q18. Describe a biogas plant in brief.

Solution

Biogas is a mixture of gases produced from decomposable organic matter by the activity of various anaerobic bacteria that can be used as a fuel.       Mechanism of biogas production: 1. The biogas plant tank is fed with a mixture of dung or waste materials from kitchen and night soil along with water. 2. The biogas tank is covered with a floating lid which keeps on rising as the gas is produced in the slurry due to the microbial activity of methanogens like Methanobacterium. 3. Methanogens grow anaerobically on cellulosic material in cowdung to produce a large amount of methane, CO₂ and H₂. 4. The biogas plant has an outlet, which is connected to a pipe to supply biogas. The leftover slurry is removed through another outlet and is used as fertiliser. 5. Biogas is used as a fuel for heating and cooking, lighting, power for irrigation and other purposes as an alternative for firewood, kerosene, electricity and LPG. It is considered as an ecofriendly and pollution free source of energy.

Q19. Milk begins to coagulate when lactic acid bacteria (LAB) are added to warm milk as a starter. Mention any other two benefits that LAB provide.

Solution

Other benefits of LAB: (i) Increase the nutritional quality of curd by increasing vitamin B₁₂ content (ii) Inhibit the growth of disease-causing microbes in the gut

Q20. Why is Rhizobium categorised as a 'symbiotic bacterium'? How does it act as a biofertiliser?

Solution

Rhizobium forms a symbiotic association with the root nodules of leguminous plants. The bacterium obtains food and shelter from the plant and the plant in turn, gets the fixed nitrogen. It multiplies as soon as it gets the rhizosphere of leguminous plants, enters inside their roots and forms root nodules. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as a nutrient.