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Class 12 Biology Chapter 10 Microbes in Human Welfare
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Microbes in Human Welfare
Chapter – 10
BIOLOGY IN HUMAN WELFARE
Very Short Answer Type Questions
Q.1. What is biofertilizer? What are its sources?
Ans: Biofertilizer are live or latents cell of specific microbes which are inoculated in seeds or seedlings with the purpose of their multiplying in soil and in turn increasing the nutrient availability to crops. Thes-e are collected from son, multiplied and preserved for use as inoculant.
Q.2. What do you meant by biopesticide? Name a biopesticide obtained from Neem.
Ans : Any organic substance like plants, microorganisms, insects etc which are used to destroy pests is called biopesticide.
Azadirachtin in a chemical substance extracted from neem to be used as biopesticide.
Q.3. What are bioreactors?
Ans : These are growth chambers for large scale multiplication of microorganism for obtaining products like proteins, enzymes, antibiotics etc. Such growth chamber is provided with nutrition, suitable temperature, moisture, pH, etc. so that the desired microbes can grow continuously.
Q.4. Which one is the first organic acid produced by microbial fermentation?
Ans : Lactic acid.
Q.5. Expand the term TPA.
Ans : Tissue Plaşminogen Activator.
Q.6. Name the blue green algae which is used as human food and its importance.
Ans : Spirulina which is a blue green algae. It is very rich in protein.
Q.7. Which one is the world’s most problematic aquatic weed. At what condition it grows abundantly?
Ans : Water hyacinth. It grows profusely when eutrophication is caused by excessive presence of nitrogen and phosphate in water.
Q.8. Name the group of organisms and the substrates they act on to produce biogas?
Ans : Methanomonas bacteria. They act on deng, organic waste etc. to produce biogas.
Q.9. Name the organism that fixes Nitrogen in symbiotic association with a water fern.
Ans : Anabaena azollae.
Q.10. What is mycorrhiza?
Ans : A kind of fungi that live in symbiotic association with the roots of higher plants. They help the plants to overcome physical and chemical stress and in addition supply phosphate to the plants.
Q.11. Name the curd forming bacteria. Mention at what temperature it can convert the milk to curd.
Ans : Lactobacillus bulgaricus. It forms curd best at 25°-30° C.
Q.12. What is SCP?
Ans : It means singlé cell protein. It is obtained from microbial cells, particularly yeast.
Q.13. Why are pectinases and proteases added to fruit juices?
Ans : These are used to clear the fruit juice by dissolving debris of fruit.
Q.14. Define organic farming.
Ans : Farming in which no chemical fertilizer, chemical pesticide, herbicide are used and only organic manure, biofertilizer and biopesticides are used is called organic farming. Rotation of crop and other sustainable measures are followed.
Q.15. What is pesticides?
Ans : The Chemicals which kill the pest are called pesticides.
Q.16. Name the first organic acid produced by microbial fermentation.
Ans : Lactic acid.
Q.17. What is the scientific name of Baker’s yeast?
Ans : Saccharomyces cerevisae.
Q.18. How do the differently written ‘Cry’ and ‘cry’ represent respectively?
Ans : To represent different endotoxins.
Q.19. Who coined the term antibiotic?
Ans : S.A. Waksman.
(B). Fill up the blanks :
Q.1. Yeast is used in preparation of ____
Ans : Wine.
Q.2. Biogas mainly contains _____and is used for cooking.
Ans : Methane.
Q.3. Vinegar is prepared from alcohol with the help of organism.
Ans : Acetobacter.
Q.4. The nutrient material for Wine and Brandy is_____ juice.
Ans : Fruit.
Q.5. Chemical fertilizers and ____ are the sources of wide spread pollution.
Ans : Pesticide.
Q.6. Single Cell Protein (SCP) provides a valuable____ rich supplement in human dict.
Ans : Protein.
Q.7. The sewage water is treated till the BOD is found to be _____
Ans : Low.
Q.8. ___ and ____ are the two biotechnologically manufactured vitamins.
Ans : Vitamin A& D.
Q.9. ____ is an antibiotic which is active against fungus.
Ans : Trichostatin.
Q.10. Trichoderma species are potentially useful as_____
Ans : Biopesticide.
Q.11. The biopesticides Azadirachtin obtained from____ plant.
Ans : Neem.
Q.12. _____ a blue green algae used as human food.
Ans : Spirulina.
Q.13. ____ grow in milk and convert it to curd.
Ans : Lactobacillus acidophilus.
Q.14. Enzyme zymase convert the sugar into _____ during fermentation.
Ans : Ethanol and Co₂.
(C). True and False :
Q.1. Aquatic fern Marsilea is an excellent biofertilizer.
Ans : False.
Q.2. Extensive use of chemical fertilizers may lead to eutrophi- cation of near by water bodies.
Ans : True.
Q.3. People recovering from long illness are often advised to take spirulina in their diet because it makes food easy to digest.
Ans : False.
Q.4. Dish washing powder contains an enzyme amylase.
Ans : True.
Q.5. Primary treatment of sewage is a biological process.
Ans : False.
Q.6. The free living fungus Trichoderma can be used for killing insects.
Ans : True.
Q.7. The most important role of microorganisms for the well being of human is sewage treatment.
Ans : False.
Q.8. Biogas is produced by the activity of aerobic bacteria on animal waste.
Ans : False.
Q.9. Saccharomyces cerevisiae is Bakers yeast.
Ans : True.
Q.10. DDT is the first commercially developed bioinsecticide.
Ans : True.
Q.11. Biofertilizers includes Blue green algae, Rhizobia and Mycorrhiza fungi.
Ans : True.
Q.12. Mycorrhiza is the association of Algae and Fungi.
Ans : False.
Q.13. Methanobacterium is used in the production of biogas.
Ans : True.
Q.14. Vit B,₁₂ content increases during the conversion of milk into curd by Lactobacillus bacteria.
Ans : False.
II. Short Questions (2 Marks):
Q.1. Explain how cyanobacteria serve as a main source of biofertilizers. Give the names of two cyanobacteria.
Ans : Cyanobacteria like NOSTOC, Anabaena etc. have ability to fix atmospheric nitrogen into soil and water. Therefore these are extensively used as biofertilizer particularly in rice field. These are easy to grow and multiply and no financial expenditure is involved. They grow easily.
Q.2. Identify the organisms.
(a) A microbes responsible for the preparation of alcohol from molasses.
Ans : Yeast.
(b) A soil microbe that forms symbiotic association with the roots of bean plants.
Ans : Rhizobium.
Q.3. What kind of microbes are present in our intestine? What are their role?
Ans : Lactobacillus bulgaricus, Lactobacillus acidophilus, bifidobacterium breve.
These bacteria secrete vitamins and maintain balance of acid and alkali, keep intestinal environment free from pathogens.
Q.4. Write notes on :
(a) Baker’s yeast.
Ans : Saccharomyces cerevisiae popularly known as yeast is used to prepare bead and therefore it is called baker’s yeast. The fungi acts on the flour and sugar and ferment them to produce the dough.
Some particular varieties of scenevisia is used to produce wine from fruit juice, malt, potato etc. and therefore such yeast are called brewer’s yeast.
Q.5. What are antibiotics? How they are able to prevent the growth of other microbes in media.
Ans : Antibiotics are substances of microbial origin which kill or inhibit the growth of other organisms. During cultural of particular microorganism in media some other unwanted microbes may grow. Therefore to prevent growth of unwanted bacteria particular antibiotic is used in the medium.
Q.6. What is sewage? In which way can sewage be harmful?
Ans : Sewage is the discharge coming out from houses, factories, slaughter house, cow shed, open toilets and such other places and ultimately flow into nearby water bodies, lake or river.
Sewage contains harmful substances, pathogens, toxins etc. and therefore if it mixes up with drinking water it may cause serious harm. Bathing in such polluted water also harmful.
Q.7. Discuss giving examples the statement ‘Legumes fertilize the soil but cereals do not’.
Ans : Leguminous plants herbour nitrogen fixing symbiotic bacteria called Rhizobium and therefore cultivation of legumes fertilize the soil by adding nitrogen. Cereals do not possess any nitrogen fixing bacteria in their roots and therefore they cannot enrich the soil with nutrients.
Q.8. What is mycorrhiza? How does it help as a biofertilizer?
Ans : Mycorrhiza is a symbiotic association of some types of fungi with the roots of higher plants. They not only help in phosphate nutrition of the plants but also help in overcoming of resistance due to draught, cold and other environmental stress. Therefore suitable types of mycorrhiza are used as biofertilizer for crop cultivation and in silviculture.
Q.9. Are microbes can be used as a source of energy? If yes how?
Ans : Methane gas is inflammable and can be used as fuel for various purposes. Methane is obtained from decomposing organic matter, sewage and from reserve under the earth. Methanomonas bacteria are used for biogas production from decomposition of organic waste. Ethanol is another kind of fuel which can be obtained from fermentation of carbohydrate by yeast and some specific microbes. It is popularly called biofuel.
Q.10. Discuss the biological significance of Azolla pinnata in agriculture.
Ans : Azolla Pinnata is a free floating aquatic pteridophyte which contains a symbiotic cyanobacteria Anabaena azollae which has the capacity to fix atmospheric N, and excretes the nitrogenous compounds in to the cavity of ferm. In agricultural field specially in rice field it increases the nitrogen content.
Q.11. What is the chemical nature of bio-gas? Name an organism involved in biogas production.
Ans : Biogas is a mixture of methane carbon dioxide, hydrogen sulphide and ammonia.
The biogas is produced by a special category of bacteria called methanogens and common methanogens are methanobacterium and methanococcus.
Q.12. Name the microbes used for the production of following-
(a) Citric acid.
(b) Acetic acid.
(c) Butyric acid
(d) Lactic acid.
Ans :
| Product | Microorganism |
| (a) Citric acid | Acetobacter aceti |
| (b) Acetic acid. | Aspergillus niger |
| (c) Butyric acid | Clostridium butylicum |
| (d) Lactic acid. | Lactobacillus delbrueckii |
III. Short Questions (3 marks each) :
Q.1. What do you mean by organic farming? Why it is suggested to switch over to organic farming from other types?
Ans : Organic forming is an agricultural system that seeks to provide the consumer, with fresh, tasty and authentic food while respecting natural life-cycle systems. In this type of farming no unnatural substances like chemical fertilizer, chemical pesticides, chemical herbicides are used.
To achieve this, organic farming relies on a number of objectives and principles, as well as common practices designed to minimise the human impact on the environment, while ensuring the agricultural system operates as naturally as possible.
Typical organic farming practices include :
(a) Wide crop rotation as a prerequisite for an efficient use of onsite resources.
(b) Very strict limits on chemical synthetic pesticide and synthetic fertiliser use, livestock antibiotics, food additives and processing aids and other inputs.
(c) Absolute prohibition of the use of genetically modified organisms.
(d) Taking advantage of on-site resources, such as livestock manure for fertiliser or feed produced on the farm.
(e) Choosing plant and animal species that are resistant to disease and adapted to local conditions.
(d) Raising livestock in free-range, open-air systems and providing them with organic feed.
(e) Using animal husbandry practices appropriate to different livestock species.
Organic farming sustainable use of resources do not pollute the soil and environment and ensure supply of healthy food and therefore it is suggested that farmers should switch over to organic farming.
Q.2. What are biogas? Give its composition. Why is biogas preferred to other conventional energy fuels.
Ans : The gas produced by methane bacteria by decomposing organic waste is called biogas.
The gas mainly composed of methane. Other gases loke carbon dioxide, carbon monoxide, sulphur are also present in minute quantities.
Biogas is preferred to other fuel as because it is renewable, less costly and easy to produce. The technology is simple and finally the end product of decomposition can be used as manure. We have huge potentiality of producing biogas as we waste a huge sewage which can be used profitably for biogas production. Moreover it is suitable for farmers and villagers because the raw materials needed for the production of biogas is plenty. Conventional energy is costly and non- quantity of organic waste and renewable in the sense that it uses exhaustible natural resources.
Q.3. Lactic acid bacteria inhibit in what kind of food. Mention some of its useful applications.
Ans : Lactic acid bacteria prefer milk and milk like substances and in. addition it is also found in malt molasses, lactose, maltose etc.
Lactic acid bacteria are used in
(a) obtaining lactic acid.
(b) polymer production.
(c) leather industries. and
(d) plastic industries.
Q.4. How are biofertilizers different from fertilizers such as NPK sold in the market. Discuss the role of Rhizobium as a biofertilizer.
Ans : Biofertilizers are live or latent microbes which on inoculation increase their number in soil or in roots and carry out nutrition enhancement either by fixing atmospheric nitrogen or by dissolving phosphate or by secreting micronutrients etc. Their number gradually increase in soil and continue to help maintain fertility of the soil. NPK on the other hand is a mixture of chemical fertilizer. It serves only limited purpose of supplying a particular type of nutrition and for a specific duration and purpose. It is not multipurpose in nature. It discourage growth and development of indigenous microflora. Excessive use of it destroy the natural biological propertiès of soil.
Rhizobium is a symbiotic nitrogen fixing bacteria live in association with the roots of legumes. Cultivation of legumes therefore increase nitrogen content of the soil. It is practice to cultivate legumes as inter crop between major crops. It is therefore a kind of biofertilizer and can be inoculated artificially while cropping legumes.
Q.5. What are flocs? State their role in effluent treatment and their fate in sewage treatment tank?
Ans : During secondary treatment sewage a huge quantity of microbes grow and consume oxygen. To keep supply required oxygen the water containing sewage is vigorously stirred by rotation. This causes accumulation of waste in the surface in the form of some circles. These are called flocs.
These flocs contain huge quantities of aerobic microorganisms and are decomposed quickly. Some quantity of it is removed to primary tank for further treatment of fresh sewage.
Q.6. What is the full form of VAM? What is its role? Give at least two examples each endo and ecto mycorrhiza.
Ans : Vesicular Arbuscular Mycorrhiza. VAM are symbiotic association of some fungi with the roots of higher plants. They enhance phosphate nutrition of the plants by supplying dissolved phosphate to the plants. So plants in phosphate deficit soil also can grow. In addition to phosphate nutrition the VAM can ameliorate conditions favourable for the growth of plant even under severe physical and chemical stress.
Example of – Endomycorrhiza : Glomus, Gigaspora,
Ectomycorrhiza: Boletus, Amanita.
Q.7. Explain the role of baculoviruses as a biological control agents. Mention their importance in organic farming.
Ans : Baculoviruses are the pathogenic viruses which infect and kill many insect pests and other anthropod pests. Most important baculoviruses involved in biological control is nucleopolyhedro virus. These are species specific and have narron spectrum insecticidal effect so don’t have any negative effect on other organisms, even non-target insects.
These are used to control the pest of potato like potato beltle, aphids and corn borer etc. It is also used for the production of organic fertilizers and help in organic farming.
| Sl. No. | CONTENTS |
| Chapter 1 | Reproduction in Organisms |
| Chapter 2 | Sexual Reproduction in Flowering Plants |
| Chapter 3 | Human Reproduction |
| Chapter 4 | Reproductive Health |
| Chapter 5 | Principles of Inheritance and Variation |
| Chapter 6 | Molecular Basis of Inheritance |
| Chapter 7 | Evolution |
| Chapter 8 | Human Health and Disease |
| Chapter 9 | Strategies for Enhancement in Food Production |
| Chapter 10 | Microbes in Human Welfare |
| Chapter 11 | Biotechnology: Principles And Processes |
| Chapter 12 | Biotechnology and its Applications |
| Chapter 13 | Organisms and Populations |
| Chapter 14 | Ecosystem |
| Chapter 15 | Biodiversity and Conservation |
| Chapter 16 | Bioresources of Assam |
| Chapter 17 | Environmental Issues |
Q.8. Discuss the role of microbes in sewage treatment.
Ans : Sewage or waste water contain excreta, industrial and agricultural waste, It contain water and 0.5.-1% organic or inorganic matters. The solid remains, suspended cellulose, lingo cellulose, proteins, fats etc. are found in colloidal form. The inorganic materials remain in dissolved state. Detergent, paints, toxic chemicals. Cellulose matter etc. are discharged by industries chemical fertilizer, pesticides, herbicides, animal excreta etc. are discharged due to agriculture operation. Sewage is a store house of pathogens. It is therefore necessary to treat the sewage before releasing. Removing harmful and polluting substances is difficult. However, microbial treatment can be done to clean it partially. The heterotrophic microbes are used which digest organic residue under aerated condition.
The treatments are done in two stages :
(i) Primary treatment : Primary treatment is the physical removal of 20-30% organic materials present in sewage. This is done by screening, precipitation of small particulate matters, filtration and sedimentation. The sludge that form due to such treatment is removed and the required portion is piped into aeration tank for secondary treatment.
(ii) Secondary treatment : It is a biological treatment done in aeration tank. A large variety of microbes remain present in it. Constant agitation cause aeration which help quicker decomposition of organic substances. A large number of aerobic microbes grow in the process. Sometime, the filamentous microbes and bacteria together form a mesh like structure over the surface. With the gradual consumption of organic materials, the number of microorganisms present in affluent is reduced due to reduced availability of organic substances. This lower the biological oxygen demand (BOD) of the affluent. More the number of microbes more will be the demand for oxygen in the affluent. Till the BOD is significantly reduced the aeration of the tank continues.
After significant reduction of BOD the affluent is removed to settling tank where all remaining sludge including the aerobic microbes, dead and living will settle down. This sludge is called activated sludge. The remaining sludge is removed to another tank called anaerobic sludge digester. Here the anaerobic bacteria will digest the aerobic microorganisms carried over by the sludge. Anaerobic bacteria while digesting the organic remains produce a mixture of gases such as methane, hydrogen sulphide, carbon dioxide etc. After the anaerobic treatment the affluent is released into natural water bodies.
Till now no other method of treatment has been successful. This process is carried out all over the world.The treatment of sewage has assumed great importance now as more and more urban localities are coming up all over the globe and as a result more sewage is generated. In India the river Ganga and Yamuna are becoming more and more polluted due to the fact that more urban settlements have grown up on the banks of these rivers. Government has therefore framed two Action plans called Ganga Action Plan and Yamuna action plan to be supervised by the Ministry of Environment and Forests.
Q.9. What are antibiotics? Name any two micro organisms with their products used in the production of antibiotics.
Ans : Antibiotics are substances, primarily produced by certain harmless micro organism which in law concentrations are antagonistic to the growth of other microorganisms such as pathogenic bacteria. Etymologically, antibiotics means against life’
| Micro ganism | Antibiotics |
| Streptomyces auriofac:ens | Tetracycline. |
| Streptomyces Fradiae | Neomycin. |
IV. Long Questions 5 Marks :
Q.1. What is sustainable agriculture? Discuss the role of biopesticides and biofertilizers in sustainable agriculture.
Ans : Sustainable agriculture means an agricultural practice in which the quality of soil is maintained without application of any external source of energy, fertilizer, pesticide etc. The productivity of soil is maintained as it is years after years by following natural practices like use of biofertilizers, biopesticides, crop rotation, conventional crop improvement method, suitable crop ecology and so on.
Role of Biopesticides : With the aim-of eradicating pest from crops the farmers use pesticides randomly. In that process not only the target pest die but also many non-target organisms also die. We know that all insects and such other organisms are not harmful. Only a few of them sometime cause harry. Generally in nature each type is counter balanced .by the other. So in a population no particular type gets predominance over the other, because one checks the other and thus there exl. population balance in an ecosystem. However, due to over utilization of ecosystem potentiality monocropping, eradication of host plants etc some pests have been eradicated giving space for others. In the absence of one the other gets predominance and become harmful for the crop. It is normal circumstances one counter balances the other and thus their population sizes remain controlled.
The chemical pesticides are not only harmful for non-target organisms but also to health human being, animal and the environment as a whole. Such chemical pesticides persist for ion in the environment as they breakdown slowly.
Bio-control of pest is a good option if used judiciously. The principle of bio-control! is that one organism is used against other in a judicious manner so that the one that cheeks the other does not in turn become a menace. For this purpose the mode of life and action of most such organisms must be studied in detail including their host, predisposing condition, life-cycle etc.
Role of Biofertilizer: In one hand the use and cost of inorganic fertilizer are on the rise and on the other hand the organic fertilizer becoming scarce day by day because the dung and agricultural waste are being used for
various other purposes. The production of inorganic fertilizer is limited by the dwindling energy resource such as petroleum and coal. The cost of production is also increasing day-by-day. Moreover the constant use of inorganic fertilizer on soil brings some adverse effect on the soil metabolic processes and ultimately renders the soil into a dead unproductive mass. In view of the above facts attention has been given to the use of such substances which in one hand increase fertility of the soil and on the other hand do not cause any adverse effect on the soil. This has led to the development of the idea of using biological processes for increasing fertility of the soil. This idea was existed since ancient time among farmers all over the world. Only in recent time the scientific basis of such belief has been explained and effort is being made to popularise the idea.
Q.2. What are organic acids? Give an account on different kinds of organic acids manufactured in the industry with the help of respective microbes.
Ans : An acid made up of molecules containing organic radicals; acetic acid, citric acid, which contain the ionizable – COOH group. Organic acids are manufactured both chemically and biologically. Here we mean organic acids manufactured using microorganisms. Some microorganisms have the ability to convert organic substances into organic acids by fermentation. For this purposes we need to supply appropriate raw materials, appropriate fermentation conditions, refining process etc. to obtain the products. The acids so obtained are comparable equally with the products obtained through chemical method and in some cases superior also. The advantage is that it is less costly use waste materials do not pollute the environment and is easy to operàte.
Some organic acids:
| Acids | Organisms |
| Citric acid | Aspergillus niger |
| Acetic acid | Acetobacter aceti |
| Butyric acid | Clostridium butylicum |
| Lactic acid | Lactobacillus delbrueckii |
3. Draw a diagrammatic sketch of a biogas plant and label its components.
Ans :
Q.4. Describe the main idea behind biological control of pests and diseases. Give at least two examples each from biopesticides and bioinsecticides.
Ans : Biological control of pests and disease arose from the fact that chemical pesticides, fungicides,bactericides are harmful to the non-target organisms which are beneficial to our agriculture. Moreover the chemicals are harmful to the environment in many ways. These chemical enter into human animal and microbial cells, through food chain and undergoes biomagnifications. In addition to all these the chemical pesticides etc. are costly also.
Aspects of Biological Controls :
(i) It control the pest effectively.
(ii) It is not polluting the environment.
(iii) It is easy to use.
(iv) It is a permanent method.
Bioinsecticides: Biostorm VBT.
Biopesticide : Trichoderma viridal Bacillus thuringiensis.
Q.5. In which way sewage can be harmful to us? Mention the principle of sewage treatment. Write the key differences found in between primary and secondary sewage treatment.
Ans: Sewage contain a large quantity of harmful substances such as disease causing germ, toxins chemicals, dirty matters, drainage materials from industries, factories, latrines and so on. These mix up with drinking water, as these find outlet into river, lakes and sometime tanks. Use of this kind of water is harmful.
Sewage Treatment: Sewage or waste water contain excreta, industrial and agricultural waste. It contain water and 0.5- 1% organic or inorganic matters. The solid remains, suspended cellulose, lingo cellulose proteins, fast etc. are found in colloidal form. The inorganic materials remain in dissolved state. Detergent, paints, toxic chemicals, cellulose matter etc. are discharged by industrial. Chemical fertilizer, pesticides, herbicides, animal excreta etc. are discharged due to agriculture operation. Sewage is a store house of pathogens. It is therefore necessary to treat the sewage before releasing. Removing harmful and polluting substances is difficult. However, microbial treatment can be done to clean it partially. The heterotrophic microbes are used which digest organ residue under aerated condition. The treatments are done in two stages –
(i) Primary Treatment: Primary treatment is the physical removal (1) of 20-30% organ materials present in sewage. This is done by screening precipitation of small particulate matter filtration and sedimentation. The sludge that form due to such treatment is removed and the required portion is piped into aeration tank for secondary treatment.
(ii) Secondary Treatment: It is a biological treatment done in aeration tank. A large variety of microbes remain present in it. Constant agitation cause aeration which help quicker decomposition of organic substances. A large number of aerobic microbes grow in the process. Sometime, filamentous microbes and bacteria together form a mesh like structure over the surface. With gradual consumption of organic materials, the number of microorganisms present in affluent reduced clue to reduced availability of organic substances. This lower the biological oxygen demand (BOD) of the affluent. More the number of microbes more will be the demand oxygen in the affluent. Till the BOD is significantly reduced the aeration of the tank continue.
Q.6. What are enzymes? Name some major enzymes used in industry and explain their importance.
Ans : Enzymes are proteinaceous substances of biological origin and catalyse the specific biochemical reactions. A number of enzymes have been commercially produced by the metabolic activities of microbes, especially different species of fungi.
Microbial source and use of enzymes.
| Enzyme | Microbial source | Usess |
| 1. Lipases | Candida lipolytica (fungus) laundry. Also used in | Used in detergents to remove the oil stains from the flavouring of cheese. |
| 2. Proteases and pectinases | Aspergillus niger (fungus) | For clarification of fruit juices. |
| 3. Streptokinase | Streptococcus (bacterium) | Used as a ‘clot buster’ to dissolve the blood clot in the blood vessels of the patients suffering from myocardia infarction, so is fibrinolytic. |
| 4. Glucose oxidase. | Penicillium chrysogenum | (Fungus) |
| 5. Invertase | Saccharomyces cerevisiae (yeast) | Hydrolysis of sucrose, so also called sucrase. |
| 6. α -Amylase | Rhizopus japonicus and R. oryzae (fungus) | Digestion of starch and preparation of soft centred candles.Also in softening and sweetening of bread. |
| 7. Dextran | Leuconostoc mesenteroides | Polymerization of simple sugars to form dextrins. |
Q.7. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
Ans : The key role of fertilizers and their judicious use in crop husbandry is well understood, when one is familiar with the general facts about plant nutrition. Most of the plant nutrients, besides carbon, hydrogen and oxygen, originate from soil. The soil system is viewed by soil scientists as triple phase system of solid, liquid and gas. The use of fertilizers has caused short term increases in agricultural productivity. Use of fertilizers to the soil is an essential component of modern agricultural system.
Indian soils are usually very poor in organic matter as well as in nitrogen.Constant leaching (dissolution in water) and harvesting or crops deprive the soil of mineral contents. It is estimated that different agricultural crops in India remove above 4.27 million tonnes of nitrogen, 2.13 million tonnes of phosphoric acid, 7.24 million tonnes of potash and 4.88 million tonnes of lime every year.
The total consumption of fertilizers in India is about 9.2 Million tonnes and was expected to touch 20 million tonnes by the end to twentieth century. Fertilizers are inorganic materials containing elements in the form of soluble or readily available chemical compounds. In common parlance, the fertilizers are sometimes called chemical, artificial or inorganic manures. Green manures, biofertilizers and biological control methods have been introduced to combat the ill effects of agricultural chemicals.
The ill-effects of chemical fertilizers are:
(a) They are expensive.
(b) Their manufacture depends upon the dwindling resources of energy as petroleum and coal etc.
(c) Their production releases pollutants.
(d) They are lost readily when applied in field by surface run-off and thus pollute soil and other water resources.
Biofertilizers are organisms which can bring about soil nutrient enrichment. The main sources of biofertilizers are bacteria, cyanobacteria and fungi.
(i) Bacteria as N₂ fixers :
(a) Legume – Rhizobium symbiosis. At present the primary nutrient, limiting agricultural yields is nitrogen. Some plants are capable of producing more nitrogen than they consume. These plants show symbiotic relationship with nitrogen fixing bacteria, Rhizobium bacteria produce root nodules in leguminous plants. It has the capacity to fix free nitrogen. Root nodules of legumes differ considerably in shape and size. They may be spherical, elongated, flat etc.
(ii) Cyanobacterial as N₂ fixers. Some of the cyanobacteria (blue green algae) are important nitrogen fixers of rice fields. Nearly 40 species of blue green algae are known to fix nitrogen. These plants usually bear thick walled, hyaline heterocysts, which is thought to be the site of nitrogen fixation. Some of the nitrogen fixers are Anabaena, Nostoc, Aulosira. They derive their energy by photosynthesis. They are being widely used a biofertilizers in institutes like IARI, New Delhi and 20, 30 kg/ha of nitrogen is fixed by them.
(a) Azolla – Anabaena symbiosis. Among the symbiotic cyanobacteria (blue – green algae Anabaena azollae occurs as an end phyte in the leaves of Azolla pinnata which is free floating aquatic pteridophyte. It has the capacity to fix atmospheric nitrogen and excretes the nitrogenous compounds into the cavity of the fern.
(b) Anabaena cycadae lives in the coralloid roots of gymnosperm Cycas.
(c) Azolla and Nostoc (Cyanobacteria) are added in the agricultural fields to increase the rice yield by more than fifty percent.
It has been estimated that blue green algae can provide 7-8 lakh tonnes of fixed nitrogen, equivalent to 15-17 lakh tonnes of urea. Thus entire needs of nitrogen supply to rice crop can be provided through nitrogen fixed by blue-green algae. Further these nitrogen fixers are based on simple technology and bear low cost.
(ii) Mycorrhizae: It refers to symbiotic association between the fungus and roots of higher plants. These are more commonly found in oligotrophic soils. Mycorrhizae are formed by many members of genus Glomus. These can be classified into two types:
(a) Ectomycorrhizae: Here, fungal mycelia form mantle on root surface. From the mantle, fungal hyphae penetrate into cortex of (n) root as well as into the soil. This leads to increase in surface area for absorption of water and minerals (N,P and K). Fungal hyphae in soil further solubilize some insoluble organic compounds which are easily absorbed by plants. Ectomycorrhizae have been found in oaks, pines, Fagus and Eucalyptus. Plants with mycorrhizal roots are resistant to root-borne pathogens, tolerance to salinity and drought and with increased growth and development.
(b) Endomycorrhizae: Here, fungus does not form a mantle on root surface, instead it produces loosely interwoven hyphae. Some of these mycelia penetrate into soil. Still some other hyphae enter into cortex of root.
Endo mycorrhizae have been reported in certain orchids and woody plants. They are produced by septate as well as non-septate fungi. In the cortex hyphae grow intracellularly and some penetrate the cells to form vesicles or finally branched hyphal coils called arbuscules. Such association is also called vesicular arbuscular. Such association is also called vesicular-arbuscular mycorrhizae or VAM. VAM have shown their importance in phosphate nutrition of plants. Mycorrhizal are known to accumulate more nutrients per unit area of the host. Mycorrhizae association reduces the dependency on synthetic fertilizers and converts the marginal soil into a productive field.
Q.8. Discuss briefly what would happen if a large volume of untreated sewage is discharged into a river.
Ans : If untreated sewage is discharged into the river the following problems would happen :
(a) Excess of nitrates from fertilizers will increase in river water which will help in eutrophication.
(b) Organic pollutants like phenol, naphtha, proteins, cellulose, aromatic compounds will increase in water.
(c) Radioactive elements will increase in the water which may affect the aquatic animals.
(d) Cadmium mixing with water may result itai disease which may lead to the cancer of liver and bone.
(e) The water may have sand, clay, silt, etc. along with fecal water, bacteria, paper, fibers, etc. which are harmful for us.
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