Microbes In Human Welfare - Class 12 Medical Biology - Extra Questions

Match Column-I with Column-II and select the correct option using the codes given below.

Cyclosporin A, a Trichoderma product, is an immunosuppressant that blocks the activation of T helper cells and interferes with the release of interleukin-2 and thereby prevents organ rejection in transplantation processes. Statins are the competitive inhibitor of enzyme HMG-CoA reductase, an enzyme of cholesterol biosynthesis and are produced by Monascus species. Clostridium butyricum is anaerobic bacteria that produce butyric acid. Aspergillus sp. produces citric acid through fermentation. 
Therefore, the correct answer is option D.


What are biofertilizers? Give an example.

The term biofertilizer denotes all the nutrient inputs of biological origin (microbes producing nitrogen compounds) for plant growth. Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria (blue-green algae). E.g.: Azotobacter, Rhizobium.


Answer in one sentences:
Mention the use of statin.

Statin is a type of drug used to lowers the cholesterol. It is produced by the fungi Aspergillus and Penicillium as a secondary metabolite.


How do bacteria and cyanobacteria increase soil fertility? Explain.

Fertilizers can be expensive agricultural inputs for small-scale farmers, but there are technologies being developed which can offer farmers less expensive ways to ensure their soils are fertile and healthy.

Cyanobacteria, or blue-green algae, is one such example of a bio-fertilizer, a type of organic fertilizer which contains living organisms and harnesses naturally occurring inputs like solar energy, nitrogen, and water to ensure soil fertility and plant growth. Small-scale farmers using bio-fertilizers have the potential to provide larger and more sustainable yields and healthier soils for themselves and their communities.

Micro-organisms are the most essential resource for a farmer because they nourish soil with essential nutrients. Soil contains numerous minerals in forms which plants cannot absorb directly. Microbes like fungi and bacteria with the help of their enzymatic machinery break down these minerals into forms that can be absorbed by crops. Along with essential elements, microbes also provide one of the most influential factors required for overall development of plants - plant hormones. Some of these plant hormones play crucial roles in seed formation, growth and ripening. These hormones also impart immunity against invading pests.
 




What is the role of micro-organism in increasing the fertility of the soil?

The use of the chemical fertilizers to meet the ever-increasing demand of agricultural produce has contributed significantly to environmental pollution. So, microorganisms help in increasing the fertility of the soil. The microorganisms which are used for increasing fertility of the soil are known as biofertilisers and this type of farming is known as organic farming. Biofertilisers provide optimum nutrients to crop plants. They enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.
  1. Bacteria: Rhizobium forms the symbiotic association with root nodules of leguminous plants. These bacteria fix atmospheric nitrogen into organic forms, which is used by plants as nutrients. Bacteria like Azospirillium and Azotobacter can fix atmospheric nitrogen while free-living in the soil, thus enriching the nitrogen content of the soil.
  2. Fungi: Fungi also forms symbiotic associations with roots of higher plants, known as Mycorrhiza. The fungal symbiont absorbs phosphorus from soil and passes it to plants. In return, fungi get shelter and food from this association.
  3. Cyanobacteria: Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen e.g., Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue-green algae also add organic matter to the soil and increase its fertility.


Name two bacteria which are used as biofertilizer.

Bacteria used as biofertilizers are:
1. Rhizobium
2. Azotobacter



How can sewage be used to generate biogas? Explain.

Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. Biogas is a renewable energy source. It can also be used in a gas engine to convert the energy in the gas into electricity and heat. Stages in biogas production Biogas is produced using well-established technology in a process involving several stages: Biowaste is crushed into smaller pieces and slurrified to prepare it for the anaerobic digestion process. Slurrifying means adding liquid to the biowaste to make it easier to process. Microbes need warm conditions, so the biowaste is heated to around 37 °C. The actual biogas production takes place through anaerobic digestion in large tanks for about three weeks. In the final stage, the gas is purified (upgraded) by removing impurities and carbon dioxide. After this, the biogas is ready for use by enterprises and consumers, for example in a liquefied form or following injection into the gas pipeline network.


Why is a starter added to set the milk into curd? Explain?

Pasteurized milk is heated to a temperature of 30-40$$^{0}$$C, or even at room temperature or refrigerator temperature, and a small amount of old curd or whey added to it, the lactobacillus in that curd or whey sample starts to grow. These convert the lactose into lactic acid, which imparts the sour taste to curd. When a small amount of starter is added to milk, it gets converted to curd. The curd when added into the milk, the Lactic acid bacteria present in the curd cause coagulation of casein which convert into curd. Curds are a dairy product obtained by curdling (coagulating) milk. The coagulation can be caused by adding rennet or any edible acidic substance such as lemon juice or vinegar, and then allowing it to set. The increased acidity causes the milk proteins (casein) to tangle into solid masses, or curds. Milk that has been left to sour (raw milk alone or pasteurized milk with added lactic acid bacteria) will also naturally produce curds and sour milk cheeses are produced this way. 


Why do curd sets faster in summer than in winter?

Milk is converted into curd by bacteria $$Lactobacilli$$. Bacteria grow faster in summer, as they require warm temperatures to grow. Thus, they set curd faster in summer than in winter.


Define: Biofertiliser

Biofertiliser : Living organisms which are used as fertiliser to supply the nutrients to plants, are called biofertilisers. For example, blue green algae, which fix nitrogen in soil, (and hence enhance fertility of rich fields) are called biofertiliser.


Mention the role of cyanobacteria as a biofertiliser.

Biofertilisers are substances which contain microorganisms which bring about the nutrient enrichment of soil by enhancing the availability of nutrients to crops. Cyanobacteria have the property of nitrogen fixation and hence, they add organic matter as well as nitrogen to the soil.


(a) How do organic farmers control pests? Give two examples.
(b) State the difference in their approach from that of conventional pest control methods.

a) Organic farmers control pests by one of the following ways:
i) Avoiding the pest- Farmers can avoid pests by moving the crop to a new location. For example, potato industry in San Louis valley of Colorado is surrounded by mountains which protect the plants from aphids. 
ii) Finding genetic resistance- Farmers find new resistant varieties from seed banks. Potatoes can be genetically engineered to protect them from blight disease using wild varieties. 
b) The difference in the approach of organic farmers is that they use organic fertilizers which are neither harmful to plant nor to its environment. In conventional pest control methods, the pesticides used may leach into the soil because of heavy rainfall, the texture of the soil etc., leading to contamination of the ground water.


Name a genus of baculovirus. Why are they considered good bio-control agents?

$$Nucleopolyhedrovirus$$ is a genus of baculoviruses used as biological control agents.
They are considered to be good bio-control agents as they act with high specificity on many serious arthropod pests. They do not harm the plants, mammals. 


What are methanogens? How do they help to generate biogas?

The group of methane-producing anaerobic bacteria is called as methanogens.
Biogas is a mixture of methane and carbon dioxide. Methanogens produce methane, carbon dioxide and hydrogen gas by the anaerobic digestion of cellulosic plant part. Thus, methanogens helps in producing biogas.


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

The symbiotic association between fungi and plants are called as mycorrhiza in which fungi absorbs phosphorus from soil which is then used by plants as nutrients. Hence, mycorrhiza can be used as biofertilisers. The fungi which belongs to genus Glomus forms mycorrhiza.


In which way have microbes played a major role in controlling diseases caused by harmful bacteria?

The antibiotics are substances produced by the natural metabolic processes of spore-forming aerobic bacteria and fungi as their natural defense against other microorganisms. Among bacteria and fungi, bacterial genera outnumber the fungal genera in the production of antibiotics. The highest numbers of antibiotics are derived from bacterial genera Streptomyces and Bacillus and fungal genera Penicillium and Cephalosporium. These antibiotics are used to control the disease-causing bacteria.  


Name any two species of fungus, which are used in the production of the antibiotics.

Antibiotics are the chemical substance produced by the microorganisms like bacteria and fungi and used in the treatment and prevention of diseases that are caused by other bacteria and parasites. They may either kill or inhibit the growth of bacteria.
The common species of fungus used in the production of antibiotics are:
1. Penicillium notatum which is the source of Penicillin.
2. Cephalosporin acremonium which is the source of Cephalosporin. 


In which food would you find lactic acid bacteria? Mention some of their useful applications.

Lactic Acid bacteria is found in the curd. These bacteria convert lactose sugar into lactic acid thereby promoting the formation of milk into curd. Lactic acid bacteria (LAB) have historically been used as starter cultures for the production of fermented foods, especially dairy products. Lactic acid bacteria (LAB) are widely used in many fields of human activity and especially in food preservation and in medicine. They are used for the synthesis of many heteropolysaccharides and homopolysaccharides. 


Name some traditional Indian foods made of wheat, rice and Bengal gram(or their products) which involve use of microbes.

Bread from wheat, dosa from rice and Khandvi from Bengal gram use microbes for fermentation during dough formation. Anaerobic fermentation by Saccharomyces cerevisiae serves the purpose.


How do biofertilisers enrich the fertility of the soil?

Answer:
  • A biofertilizer is a fertiliser made up of living microorganisms.  
  • When applied to the field it promotes plant growth by increasing the supply or availability of primary nutrients to the host plant.
  • This helps in increasing the fertility of the soil.
  • Many species of bacteria and cyanobacteria have the ability to fix free atmospheric nitrogen.
  • One of the major advantages of biofertilizers is they are eco-friendly and cost-effective.


Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.

Biopesticides and bioinsecticides are the living organisms that specifically inhibit the growth of pest and insects e.g., Bacillus thuringiensis (Bt) is a gram-positive bacterium that produces crystal proteins which are potent and highly specific insecticides. Trichoderma harzianum is a bio-fungicide and is used for suppression of various disease-causing fungal pathogens. Biofertilizers are the microorganisms which increase the nutrient availability from soil to plants thereby causing nutrient enrichment, for example, free-living and symbiotic nitrogen fixing bacteria and Cyanobacteria.


Find out the name of the microbes from which Cyclosporin A(an immunosuppressive drug) and Statins (blood chloestrol lowering agents) are obtained.

Cyclosporin A, a fungal product (Trichoderma polysporum), is an immunosuppressant that blocks the activation of T helper cells and interferes with the release of interleukin-2 and thereby prevents organ rejection in transplantation processes. Statins are produced by Monascus purpureus. Statins are competitive inhibitor of enzyme HMG CoA reductase, an enzyme of cholesterol biosynthesis.


Do you think microbes can also be used as source of energy? If yes, how?

Yes, Microbes can be used as a source of energy. Gober gas is a mixture of methane (CH$$_4$$), carbon dioxide (CO$$_2$$), hydrogen (H$$_2$$) and hydrogen sulphide (H$$_2$$S) with methane as a major component (65%).  Methanogens are anaerobic autotrophic bacteria that convert carbon dioxide and hydrogen into methane gas. The hydrogen serves as an electron donor for reduction of carbon dioxide. Thus, methanogens produce gober gas by anaerobic fermentation of biomass (dung) in presence of water.  


Write down the two beneficial roles of bacteria converting milk in to curd.

Bacteria like Lactobacillus helps in the production of lactic acid from lactose which is essential in the formation of curd. It lowers the pH of the milk which helps in coagulation of protein and forming the curd.  


For biological control which fungus is used in the treatment of plant diseases?

There are many different bacterial and fungal species used for the treatment of plant diseases. These organisms serve as biological agents in biocontrol. The fungi which are commonly used for the treatment is the Fusarium species. Fusarium harzianum and Fusarium virens are the fungal species which are used against Pythium, Phytophthora, Rhizoctonia, Botrytis, powdery mildew, downy mildew and Sclerotinia. 


With the help of a neat and labelled diagram explain VAM (vesicular arbuscular mycorrhizae).

VAM (vesicular arbuscular mycorrhizae) is the symbiotic association between a fungus (Phycomycetes) and the root of the angiosperm plant. The fungus helps the plants to obtain the plant nutrients from the soil. In return, plant root serves as the habitat for them. They form a network of filaments and colonises in the root system.
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Define antibiotics.

The antibiotic is a substance that inhibits the growth or kills microorganisms. These are two types - broad spectrum and narrow spectrum antibiotics e.g., penicillin, erythromycin etc.


Why are bio-fertilizers preferred over chemical fertilizers?

Biofertilizers are preferred over chemical fertilizers because they are not harmful as they contain organic materials while chemical fertilizers are made up of chemical which are harmful to the consumers. Another reason is that biofertilzers do not decreases the fertility of the soil while, continuous use of chemical fertilizers decrease the soil fertility and also results in the increase of the soil acidity. For example, anabaena, cyanobacteria and mycorrhiza acts as biofertilizer. 


Write the name of bacteria which converts milk to curd.

Lactobacillus converts milk to curd by producing lactic acid and reducing the pH of the milk. These bacteria convert the lactose into lactic acid, which imparts the sour taste to curd. 


Give the advantages of biogas.

Advantages of biogas are as followed:
$$(i)$$ It is a cheap, safe and renewable source of energy.
$$(ii)$$ It can be used for domestic lighting, cooking, street lighting as well as small scale industries.
$$(iii)$$ It burns with a blue flame and without smoke.
$$(iv)$$ It helps to improve sanitation of the surrounding.


How is Azolla helpful as biofertilizer?

Azolla is used as a biofertiliser because the leaves of this plant have cyanobacteria called Anabaena azollae. This is an algae which have the enzyme nitrogenase in the heterocysts. The heterocysts are specialised cells in the algae. These cells help in fixation of nitrogen with the help of the enzyme. The rice plants grown in these paddy fields use this fixed nitrogen. Thus, the yield of the paddy crops is increased. 


In your locality people are affected due to water scarcity. What measures will you take to deal with the problem of water scarcity?


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What is the chemical nature of biogas? Name the bacteria involved in the production of biogas.

Biogas is made up of methane (50-70%), carbon dioxide (30-40%) with traces of nitrogen, hydrogen sulphide and hydrogen. Biogas production is a multistage anaerobic digestion process. Biogas is an alternate source of energy produced by anaerobic breakdown or digestion of biomass such as animal excreta and kitchen wastes with the help of methanogenic bacteria like Methanobacterium, Methanobacillus, Methanococcus, and Methanosarcina, etc. Methanogens produce methane, carbon dioxide and hydrogen gas by anaerobic digestion of cellulosic plant part.


Write the binomials of two fungi and mention the products/bioactive molecules they help to produce.

Saccharomyces cerevisiae- This is the baker's yeast and useful in the production of alcohol. 
Aspergillus niger- This fungal species is used in the production of citric acid. 


Write the difference between manure and biofertilizers.

 Manure  Biofertilizer
It is a semi-decayed organic substance of biological origin such as cow dung.It is an organism such as bacteria which increases nutrient availability to crop plants.
It provides all types of nutrients to crop plants.It provides one or few nutrients to crop plants.
It is essential for maintaining soil structure aeration and hydration of soil.These are not essential for maintaining soil structure, aeration and hydration.


What are 'biofertilizers'? Explain them with suitable examples.

A biofertilizer is a substance which contains living microorganisms. When they are applied to seeds, plant surfaces or soil they colonize the rhizosphere or the interior of the plant. They then promote growth by increasing the supply or availability of primary nutrients to the host plant.  
Rhizobium is a soil bacterium which is found in symbiotic relation with leguminous plants. It produces root nodules and fixes atmospheric nitrogen into an organic form which is used by the plants as nutrients.
Hence Rhizobium is used as a  biofertilizer. 
Cyanobacteria are free-living or symbiotic soil bacteria. They fix atmospheric nitrogen in term of nitrates and nitrites by a biological process like Rhizobium
that increases crop yield.


Give an example of the non-edible or poisonous mushroom, studied by you.

There are two types of fungi, edible and non-edible types. There are certain fungi which are not consumed because of the production of toxins like amatoxins and phallotoxins. The fungi which produce these toxins are referred as poisonous fungi or the toadstools e.g., Fly agarics and Amanita pantherina.  The consumption of these fungi results in death due to the activity of the toxins.


Discuss the role of fungi as biofertilizers.

The symbiotic association between fungi and plants are called as the mycorrhizal association. The fungi help in absorption of the salts of phosphorus from the soil which is then used by plants as nutrients. Also, these fungal filaments increase the surface area for absorption of other mineral nutrients. Hence, mycorrhiza can be used as biofertilizers. The fungi which belongs to genus Glomus forms mycorrhiza with the roots of the plants.


Secondary treatment of the sewage is called biological treatment. Justify the statement and explain the process.

Secondary treatment removes the dissolved organic matter by the use of biological agents and hence, known as biological treatment. This is achieved by microbes which can consume and degrade the organic matter converting it to carbon dioxide, water, and energy for their own growth and reproduction. This helps to reduce the BOD of the sewage water. 


Draw a neat labelled diagram of a typical biogas plant.

The image represents the labelled diagram of the biogas plant. 
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Answer in 200 to 250 words:
Explain the role of microbes in 'Industrial products'

Microbes are used in to make many Industrial products-
1) Metabolite products- Yeast produces ethanol that is used as a solvent in various chemical processes.
2) Metal Leaching- Certain bacteria are used to leach metals such as iron from some soils and sediments.
3)  Microbes such as Rhizobium are used as bio-fertilizers which consists of living inoculants that are added to the soil to improve soil fertility and plant growth.
4) Genetically engineered bacteria is used to produce insulin. 


Describe the importance of microbes in human welfare.

1. Microbes in household products: Lactobacillus and other lactic acid bacteria (LAB) are used to convert milk into curd. The bread dough is fermented by baker's yeast. 
2. Microbes in industrial products: Microbes are used in manufacturing of beverages and antibiotics.
3. Microbes in sewage treatment: Sewage water is treated using heterotrophic microbes. During waste water treatment, microbes are used in secondary treatment.
4. Microbes in production of biogas: Certain bacteria like methanogens, anaerobically produces large amount of biogas (methane, hydrogen and carbon dioxide). 
5. Microbes as biopesticides: Microbes are used to control plant diseases and pests. Bacteria Bacillus thuringiensis is used to control butterfly caterpillars. 
6. Microbes as biofertilizer: Biofertilizers are used to increase the fertility of the soil. The main sources of biofertilizers are bacteria, fungi and cyanobacteria.


Give the microbial source of Vitamin B$$_{12}$$.

Large-scale production of Vitamin B12 is done using microbial fermentation. Vitamin B12 is produced by bacteria during their normal metabolism and thus, commercially used by culturing bacteria to produce large amounts of Vitamin B12. Vitamin B12 can be produced from various bacteria like Pseudomonas denitrificans and Propionibacterium shermanii, and Sinorhizobium meliloti.


Discuss briefly the role of microbes in household products. 

We use microbes or products derived from them everyday.
  • Curd: Micro-organisms such as Lactobacillius and others commonly called lactic acid bacteria grow in milk and convert it into curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. The starter or inoculum contains millions of LAB, which at suitable temperatures multiply, thus converting milk to curd.
  • Cheese: It is one of the oldest food item in which microbes were used. Different varieties of cheese are known by their characteristic texture, flavour and taste, the specificity is determined by the microbes used. For example, large holed Swiss cheese is ripened with the help of bacterium called Propionibacterium shermanii. Roquefort cheese are ripened by fungi Penicillium roqueforti.
  • Bread: Bread is prepared from dough, which is fermented using Baker’s yeast (Saccharomyces cerevisiae). Puffed-up appearance of dough is due to production of $$CO_2$$ during fermentation. $$CO_2$$ gas along with ethyl alcohol evaporate during baking, making bread porous and soft.
  • Dosa and Idli: The fermented preparation of rice and black gram, prepared by using bacteria.
  • Toddy: A traditional drink of some parts of southern India, is made by fermenting sap from palm known as Caryota urens.
  • Other foods: Microbes are also used to ferment fist, soyabean and bambo-shoots to make foods.


What suggestion will you give a farmer to increase the productivity of his field? Explain.

A farmer can use biofertilisers to increase the productivity of his field. Biofertilisers are the microorganisms which are used for increasing fertility of the soil. This type of farming is known as organic farming. Biofertilisers provide optimum nutrients to crop plants. They enrich the nutrient quality of the soil. They do not cause any environmental pollution. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.


What makes cyanobacteria agriculturally important?

Several unique features of cyanobacteria such as oxygenic photosynthesis, high biomass yield, growth on non-arable lands and a wide variety of water sources (contaminated and polluted waters), generation of useful by-products and bio-fuels, enhancing the soil fertility and reducing green house gas emissions, have collectively offered these bio-agents as the precious bio-resource for sustainable development. Cyanobacterial biomass is the effective bio-fertilizer source to improve soil physico-chemical characteristics such as water-holding capacity and mineral nutrient status of the degraded lands. The unique characteristics of cyanobacteria include their ubiquity presence, short generation time and capability to fix the atmospheric N2. Similar to other prokaryotic bacteria, the cyanobacteria are increasingly applied as bio-inoculants for improving soil fertility and environmental quality.


Why biofertilizers are preferred to chemical fertilizers? 

Biofertiliser is preferred over chemical fertilizer because:

1. Biofertiliser would be better in the long run because they contain organic materials while fertilisers contain chemical substances that when used in excess become harmful to the consumers.

2. Continuous application of fertilisers to the soil decreases its fertility and also leads to increase in the acidity of the soil. 

3. Fertiliser runoff from the fields also causes water pollution.



Application Based Questions :
The leaves of Azolla are used as biofertilizer. Comment upon the statement.

A blue-green alga-Anabaena azollae present in its leaf cavities. The alga fixes atmospheric nitrogen and releases nitrogenous compounds in its leaf cavities.


(a) Organic farmers prefer biological control of diseases and pests to the use of chemical for the same purpose. Justify.
(b) Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents.

a) Farmers prefer biocontrol to chemicals because usage of chemicals could be toxic to both humans and animals. Chemical pesticides are synthetic. They are broad spectrum and affect several non-target organisms. Also, chemical pesticides pollute the air, water, and soil. On the other hand, Biopesticides are live organisms or their natural products having pesticidal properties. They are pest specific and are harmless to other organisms. Biopesticides are non-pollutant. Hence, organic farmers prefer the biological control of diseases and pests to the use of chemical pesticides.
b) Bacterium : Bacillus thuringiensis
    Fungus      :  Trichoderma 
     Insect        : Ladybird and dragonflies



Describe the role of micro-organisms in industrial production.

Micro-organisms play a vital role in industrial production as:
1. Yeast and bacteria are used for bread, beer, whiskey etc.
2. They carry out process like biogas production.
3. Antibiotics are produced industrially by using microorganisms.
4. These are used in the production of organic acids such as citric acid, lactic acid etc.
5.Industrial production of enzymes.


Give two examples of microbial pesticides with their hosts.

Microbes such as bacteria, fungi, viruses, protozoan etc. and their products are used for pest control and these are known as biopesticides. Examples are:
Bacteria like: Bacillus thuringiensis
Fungi like: Merarhizium, Beauveria
Protozoa like: Schizogregrine cause diseases in insects and destroys them.


.........  is a symbiotic relationship between fungal hyphae and roots of higher plants.

Manure - It is the natural material which is obtained by decaying plant and animal waste.
Fertilizer - It is an organic or inorganic compound rich in plant nutrients
Biofertilizer- These are living microorganisms which fix nitrogen bacteria in roots of the plants.
Diazotrophs- These as bacteria that fix atmospheric nitrogen gas into a more usable form.
Root nodule- These are associated with symbiotic nitrogen fixation which occurs at roots.
Frankia-It is the genus of nitrogen-fixing bacteria which lives in symbiotic form.
Nitrogen-fixation- It is a process in which the atmospheric nitrogen is converted into ammonia.
'Mycorrhiza is a symbiotic relationship between fungal hyphae and roots of higher plants'.


Very short answer type.
What causes each of the following symptoms of inflammation: redness and pain?

Redness: increased blood flow due to vasodilation; pain injury of nerve fibres, irritation by toxins from microbes, kinins, prostaglandins.


Describe the biogas plant with a neat labelled diagram.

a) The biogas plant consists of concrete tank (10 - 15 ft deep) in which bio-wastes are collected and slurry of dung is fed.
b) A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to microbial (methanogens) activity.
c) The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses.
d) Used slurry is removed through another outlet and may be used as fertilizer.
e) The biogas thus produced is used for cooking and lighting.

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Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve the use of microbes.

Traditional Indian Foods    Microbes used
(i) Dosa, Idli (Rice)    Fermented by bacteria
(ii) Gutta (Black Gram)    Bacteria
(iii) Bread (wheat)    Baker's yeast


Describe the role of microbes in sewage treatment plant.

After the primary treatment of sewage water, primary effluent is passed into large aeration tanks, where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structures). 
While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD or Biochemical Oxygen Demand of the effluent. BOD refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water is oxidised by bacteria. The sewage water is treated till the BOD is reduced. 
The effluent is then passed into a settling tank, where the bacterial flocs are allowed to sediment. This sediment is called activated sludge. A small part of activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, other kind of bacteria which grow anaerobically, digest the bacteria and fungi in the sludge.
 During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide.

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Give examples to prove that microbes release gases during metabolism.

Dough for bread, dosa and idli swells up within a few hours of being inoculated with fermenting microbes. Heat expels the gases and makes the product spongy.


Name the microbe used in the production of citric acid.

Aspergillus niger is a fungus that is used in the production of citric acid. Apart from citric acid, it is also used in the production of other organic acid like organic acids such as citric acid and gluconic acid. It adverse conditions it causes black mould disease on certain fruits and vegetables


A farmer adds Azotobacter culture to the soil before sowing maize. How does it increase the yield of maize?

Azotobacter is a free-living nitrogen-fixing bacteria. It fixes atmospheric nitrogen in the soil and increases the fertility of the soil. Maize plants cultivated in fertile soil result in the increase in yield.


Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished?

Chemical fertilizers and pesticides are costly as well, as highly pollutant. They can be replaced by low-cost non-polluting biofertilizers and biopesticides. Biofertilizers not only provide the required nutrients to the crop plants but also improve soil texture.
Biopesticides are target specific. They do not disturb the ecosystem but reduce the number of pests and pathogens.


Find out the name of the microbes from which cyclosporin A (an immunosuppressive drugs) and statins (blood cholesterol lowering agents) are obtained.

(i) Cyclosporin A is obtained from the fungus Trichoderma polysporum. 
(ii) Statins are produced by yeast Monascus purpureus


Why are some molecules called bioactive molecules? Give two examples of such molecules.

Some molecules produced by certain living organisms, perform functions in the body of other organisms and modify metabolism. So they are termed as bioactive molecules. For examples:
(a) Cyclosporin-A:- It is used as an immunosuppressive agent in organ-transplant patients.
(b) Statins:- It has been commercialized as cholesterol-lowering agents.


The diagram is that of a typical biogas plant. Explain the sequence of events occurring in a biogas plant. Identify $$a, b, c$$
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$$a-$$ sludge
 $$b-$$ gas holder, 
$$c-$$ dung+water


Briefly describe the household products produced through the agency of microbes.

Microbes are the important components of biological systems on earth. They are present everywhere. The Microbes are also used in household products. The products are curd, dough, toddy, cheese etc.
The curd is formed by adding bacteria such as lactobacillus.
The dough is formed by fermentation caused by bacteria which is used to make bread.
Toddy is made by fermentation of sap from palm trees by bacteria.
Cheese is made by partial degradation of milk using different microbes.
Microbes are also used to ferment fish, soybean etc.


What are antibiotics? Describe the production of methodology (manufacture) of antibiotics from microbes.

Antibiotics are chemical substances that can inhibit the growth of, and even destroy, harmful microorganisms.they are derived from special microorganisms or other living systems, and are produced on an industrial scale using a fermentation process.


Discuss the role of microbes are biofertilizers.

Biofertilizers are the living microorganisms that help in the growth and development of plants or crops by enhancing the availability and supply of primary nutrients to the plant. Rhizobia are the bacteria that help in the nitrogen fixation and thus help in replenishing soil nutrients and act as biofertilizers.


What are bio-fertilizers? Describe their role in agriculture. Why are they preferred to chemical fertilizers?

Biofertilizer is a substance which contains living microorganisms which, when applied to seeds, plant surfaces, or soil, colonize interior of and promotes growth by increasing supply availability primary nutrients.
Biofertilizers are preferred because they help to get a high yield of crops by making the soil rich with nutrients and useful microorganisms necessary for the growth of the plants.


What happens when activated sludge is pumped into aerobic digester?

  • Aerobic digestion is an extension of the activated sludge aeration process whereby the waste from primary and secondary treatment is continually aerated for long periods of time. 
  • In aerobic digestion, the microorganisms extend into the endogenous respiration phase, which is a phase where materials previously stored by the cell are oxidized, with a reduction in the biologically degradable organic matter. 
  • The organic matter, from the sludge is oxidized to carbon dioxide, water and ammonia. The ammonia is further converted to nitrates as the digestion process proceeds.


Give an example for a microbial biocontrol agent.

Biological control agents are natural enemies of insect and pests. Microorganisms like bacteria, fungi are the most common biocontrol agents. An example of a microbial biocontrol agent includes Bacillus thuringiensis. It produces a toxin called as Bt toxin which is toxic to insects.


Milk starts to coagulate when Lactobacillus is added to warm milk as a starter. Mention any other two benefits of Lactobacillus.

Benefits of Lactobacillus includes:
1. It is used in the treatment of diarrhoea.
2. It is also used in the treatment of irritable bowel syndrome (IBS).
3. It is also used to treat infection caused by Helicobacter pylori, bacteria which causes ulcers.


Insulin is extracted from which microorganism?

Insulin-producing genes from the human being have been introduced into the bacteria - Escherichia coli. The genetically modified bacterium E. coli produced insulin called Humulin. This insulin is extracted from E. coli for clinical use.


Mention any four microbes used in household products.

Microorganisms are widely in used in household products. Some examples include
1. Lactic acid bacteria (LAB) like Lactobacillus acidophilus are added to milk to make curd. 
2 Baker's yeast, that is Saccharomyces cerevisiae is used to make bread. 
3. Leuconostoc and Streptococcus species of bacteria are used to make idli and dosa.
4. Single Cell Protein like Spirulina is used as supplementary food for the source of protein.


Antibiotic pencillin is made from_______.

Antibiotic penicillin is made from Penicillium chrysogenum. It is a mould-fungus that reproduces asexually with the help of conidia.


Describe secondary treatment of sewage till can be discharged into a natural water body.

  • Secondary treatment of wastewater is done to achieve a certain degree of effluent quality.
  • During this, a physical phase separation is used to remove settleable solids and a biological process to remove dissolved and suspended organic compounds.
1) The water at this stage is put into large rectangular tanks called aeration lanes.
2)  Air is pumped into the water to initiate the aerobic bacteria to break down the organic matter present within the wastewater.
3) The treated wastewater is then passed through a settlement tank where more sludge is formed at the bottom of the tank by the settling of the bacterial action
4) This sludge is collected for treatment, the water at this stage is almost free from harmful substances and chemicals. 
5) Later this water is allowed to flow over a bed of sand to remove any additional particles and is filtered.
6) The filtered water is then released into the river.


Why does milk get sour after a long time?

Milk, when left for a long time, becomes sour due to Lactobacillus in the milk that converts the lactose in the milk to lactic acid. As the amount of lactic acid in the milk increases, it results in presence of more hydrogen ions and thereby lowering of pH. Due to this milk gets sour after a long time.


Why is the yogurt very important food material?

Yogurt has many useful bacteria such as 𝘓𝘢𝘤𝘵𝘰𝘣𝘢𝘤𝘪𝘭𝘭𝘶𝘴 𝘢𝘤𝘪𝘥𝘰𝘱𝘩𝘪𝘭𝘶𝘴 which act as probiotics. These bacteria keep our intestines healthy. Apart from that, yogurt contains important vitamins such as Vitamin B6 and B12 and other elements like calcium, magnesium, sodium, magnesium etc. All these contribute to our good health.


Describe gobar gas plant in details.

Gobar gas is a mixture of methane, carbon dioxide, hydrogen and hydrogen sulphide. The major constituent of gobar gas is methane. It is produced by the anaerobic degradation of animal wastes like cow-dung or plant wastes in the presence of water. This plant has a dome-like structure built with bricks. A slurry of cow-dung and water is made in the mixing tank from where it is fed into the digester. The digester is a sealed chamber in which there is no oxygen. Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow-dung slurry. It takes a few days for the decomposition process to be complete and generate gases. It is stored in the gas tank above the digester from which they are drawn through pipes for use.


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_________is used for production for citric acid in soft drink industries.

Aspergillus niger is used for production for citric acid in soft drink industries. It is a black mould that grows on fruits like grapes and vegetables like onions.



Name the bioactive molecule that is used as an immuno suppressive agent.

The bioactive molecule is Cyclosporin-A produced by a fungus Trichoderma polysporum which is used as an immuno- suppressive agent.


List various stages of sewage treatment.

Sewage treatment generally involves three main stages:
  1. Primary treatment.
  2. Secondary treatment. 
  3. Tertiary treatment.

Primary treatment involves the temporary holding of the sewage in a quiescent basin so that the solid material should settle down and the remaining supernatant such as oil, grease and other aqueous pollutants will remain at the upper layer. 
Secondary treatment involves the removal of dissolved suspended matter. It is done by treating it with the water-borne micro-organisms in a controlled and managed habitat.
Tertiary treatment is carried out in a sensitive or fragile ecosystem. In this stage, the treated water is disinfected physically or chemically prior to release into the river stream or sea.


A farmer had been using a particular insecticide for a long time. What consequences will it have on Insect population?

If a farmer uses the same kind of insecticide for longer time, it may create resistance in insects. Hence, a long term exposure with a single type of insecticide may lead to the development of insecticide resistance species.


Why lyophilized cultures of microbes remain viable for several years?

It is a process of drying in which water is sublimed from the product after it is frozen . In this condition, lyophilized cultures of microorganisms remain viable for many years.


What is sludge?

Sludge is a semi-solid slurry that is produced from various industrial processess such as water treatment and waste water treatment etc.


Name the enzyme which is used as ' clot bluster' to remove blood clots within blood vessels.

Streptokinase (SK) is a thrombolytic medication and enzyme. As a medication it is used to break down clots in some cases of myocardial infarction (heart attack), pulmonary embolism, and arterial thromboembolism.


Write the main constituents of biogas.

Biogas contains principally methane (CH$$_4$$) and carbon dioxide (CO$$_2$$) and may have little measures of hydrogen sulfide (H$$_2$$S), dampness and siloxanes.


How do rhizobium bacteria increase the fertility of soil?

Rhizobium bacteria helps in nitrogen fixation. They form symbiotic relationship with leguminous plants.
Rhizobia are found in the soil and after infection, produce nodules in the legume where they fix nitrogen gas (N2) from the atmosphere turning it into a more readily useful form of nitrogen. From here, the nitrogen is exported from the nodules and used for growth in the legume. Once the legume dies, the nodule breaks down and releases the rhizobia back into the soil where they can live individually or reinfect a new legume host.


Write note on a typical biogas plant. How microbes help in production of biogas.

  • Biogas is a mixture of gases (predominantly methane) produced by the microbial activity which may be used as fuel. 
  • Certain bacteria which grow anaerobically on cellulosic material produces a large amount of methane along with carbon dioxide and hydrogen.
  • These bacteria are collectively called methanogens, and one such common bacterium is Methanobacterium. 
  • These bacteria are commonly found in the anaerobic sludge during sewage treatment. 
  • The biogas plant consists of a concrete tank (10-15 feet deep) in which bio-wastes are collected and a slurry of dung is fed.
  • A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. 
  • The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. 



What measures are to be taken to save paper?

The measures we can take to save paper are
1.Double-sided print papers.
2. Buy recycled papers.
3.Turning old papers into crafts
4. Recycle the paper etc.


Explain how vacuum packing slows 'spoiling' of nuts?

In vacuum, the microorganisms do not get oxygen to respire, so they do not grow in the food that is vacuum packed. As a result, the food remains protected. So, nuts are kept fresh by vacuum packing.


What are anti - biotic How do they work 

Antibiotics, also known as antibacterials, are medications that destroy or slow down the growth of bacteria.  Antibiotics work by affecting things that bacterial cells have but human cells don't. For example, human cells do not have cell walls, while many types of bacteria do. The antibiotic penicillin works by keeping a bacterium from building a cell wall.


List two advantage of using biogas.

During their development and metabolism, microbes generate methane. Different microbes generate distinct gasses based on the organic substrates they use. A biogas plant is an efficient way through microbial activity to produce energy from waste. Biogas produced from biogas plants can be used as low-cost, smoke-free burning gas to illuminate streetlights and power electric motors.


Complete the following conceptual picture related to environmental management.
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Why does 'Swiss Cheese' develop large holes?

The bacteria involved in the formation of cheese more specifically P. shermani, releases carbon dioxide when it consumes the lactic acid and forms bubbles. The bubbles don't just disappear, they form little air pockets, resulting in the holes of the Swiss cheese.


Why are some microorganisms like bacteria and fungi are important to humans? 

Bacteria and fungi are required to maintain a healthy environment. Not only do they recycle natural wastes and dead animal and plant matter, they also produce many of the nutrients that plants need to grow. Bacteria, in particular, are the only living things that can fix nitrogen for use in plants.


How does yeast make dough rise?

Fermentation is a metabolic process in which an organism converts a carbohydrate, such as starch or sugar, into an alcohol or an acid. Saccharomyces cerevisiae, commonly known as baker's yeast, when added to the dough, yeast begins feeding on the sugars in the flour and releases the carbon dioxide that makes bread rise.


Give scientific reasons.

The use of mutant strains has been increased in industrial microbiology.

Mutant varieties of microorganisms are different from the original microorganism. Mutant varieties are created by the insertion of genes of interest in a particular organism through a technique called genetic engineering. Mutant microorganisms have characteristics that are not present in the original strain and thus make them useful for various purposes. 


Describe any two uses of bacteria in industry.

Uses of bacteria in industry:
  • Leather tanning - it is brought about by sunlight with the involvement of a certain bacteria.
  • Tea curing - Different flavors of tea are produced by a certain bacteria.


Microorganisms used to increase the fertility of soil are called-

Microorganisms used to increase the fertility of soil are called-Biofertilizers.


Draw a diagrammatic sketch of biogas plant, and label its various components given below: Gas Holder, Sludge Chamber, Digester, Dung +water chamber. 


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What are biofertilisers? Give two examples. 

Organisms which enrich nutrients in soil are called biofertilisers. Azotobacter and Rhizobium are examples of biofertilisers. 


Name one phosphate dissolving bacterium.

Phosphate dissolving bacteria are Bacillus megaterium.


Give any two microbes that are useful in biotechnology. 

$$Streptococcus$$, $$Bacillus\,thuringiensis$$ - are some microbes that are useful in biotechnology.


Which bacterium is known to form crystal protein?

Bacillus thuringiensis is known to form toxic crystal protein.


Those animals or plants or microbes which destroy crops and their products are known as?

The animals or plants or microbes which destroy crops and their products are known as Pests


Why are blue green algae not popular as biofertilisers? 

Blue-green algae can proliferate in water and can carry out nitrogen fixation. But paddy is the only crop that grows in stagnant water. Most of the other crops do not need stagnant water to grow. This is the main reason of low popularity of blue-green algae as biofertiliser. 


Describe the role of micro-organisms in industrial production.

Listed below is the role:
  • Bacteria are used in coffee and tobacco processing and also to produce vinegar.
  • Bacteria can be used to produce different flavors of coffee, tea, etc.
  • Leather tanning indirectly involves the action of some micro-organisms.
  • Bacteria are also involved to make fibers that are used to make linen, rope, etc. They are obtained by fiber loosening of flax and hemp by retting.
  • Bacteria can be used in the large scale production of antibiotics, hormones, vaccines, etc.


What is the importance of the use of blue-green algae as Biofertilizers? Explain.

Blue-Green Algae or Cyanobacteria:
  • Cyanobacteria such as Anabaena, Nostoc, Plectonema, and other non-symbiotic prokaryotes perform nitrogen fixation.
  • Cyanobacteria have special cells called heterocyst. The Nif gene present in these cells does nitrogen fixation.
  • Rice fields are ideal for the growth of blue-green algae, hence the use of blue-green algae in paddy fields increases the production of rice. Nowadays, one aquatic pteridophyte called Azolla is also used along with blue-green algae as algal biofertilizer in Southern and South-East Asia.
  • The Azolla is a floating aquatic fern. Leaves of Azolla contain blue-green algae Anabaena azollae which fixes atmospheric Nitrogen. Anabaena pinata is also a good biofertilizer. When it is used in combination with Azolla, it can increase rice production by 50%.
  • Anabaena azollae is commercially produced at Central Rice Research Institute, Cuttack.


Why the efficacy of Biogas is less than Natural gas.

The capacity of Biogas is a little less than natural gas because of 31% of carbon dioxide gas present in Biogas. If the percentage of $$CO_{2}$$ is reduced then the calorific value of this gas can be increased.


Write two advantages of Blue-green algae in farming.

  • Cyanobacteria such as Anabaena, Nostoc, Plectonema and other procaryotic non-symbiotic organisms are involved in atmospheric Nitrogen fixation. Blue-green algae have a very special cell called as Heterocyst.
  • Nif gene present in heterocyst does the Nitrogen fixation. An environment of Rice field is ideal for the growth of blue-green algae: Use of blue-green algae in paddy fields increases production.
  • Use of cyanobacteria replaces the use of synthetic Nitrogen fertilizer.
  • It prevents pollution of soil and water, and eutrophication.


Which research institute is doing research on Anabaena azollae ?

Central Rice Research Institute, Cuttack is doing research on  Anabaena azollae 


How Bacillus thermogenesis is used as a biopesticide.

Bacillus thermogenesis is a soil-inhabiting bacterium. It is Gram-positive and spores of this bacterium produce a pesticide, crystal protein. These spores are being used to kill the eggs of certain insects. The first pesticide at the commercial level was made from this Bacterium.


What are Biopesticides?

Those microbes, plants, and animals which cause harm to crop or their products are called pests. Viruses bacteria Fungi, insects, or big animals may also be a pest. Those biological factors used to kill insects, weeds,  pests and pathogens are called Biopesticides. Certain viruses, bacteria, fungi, and protozoa are used as biopesticides.


What is mycorrhiza? Explain its importance.

Symbiotic association of fungi with roots of higher plants is called Mycorrhiza. The fungus absorbs nutrients from the soil and provides to host plant and in turn host plant provides nutrition to the fungus.


Observe the following figures and answer the questions :
(a) Identify the process shown in the figure. 
(b) Explain the process in short.
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a) The process represented in the picture is of production of biogas (methane) from organic waste.
b) In this process biowaste or organic waste is crushed and mixed with water to form a slurry and subjected to anaerobic digestion in digestion plant.


(i) Expand BOD.
(ii) At a particular segment of a river near a sugar factory, the BOD is much higher than the normal level. What is it indicative of? What will happen to the living organism in this part of the river?
(iii) Under what conditions will the BOD be lowered in the river? How will it affect the aquatic life?

(i) Biological Oxygen Demand
(ii) The higher BOD indicates high organic matter in river. Microbes involved in the biodegradation of organic matter in water body consume a lot of oxygen. Due to this, a sharp decline occur in the amount of dissolved oxygen. This leads to killing of fish and other microorganisms in that part of river.
(iii) BOD of water body decrease when the amount of organic matter decreases. Thus, microbes do not need oxygen for its decomposition.
Due to the decreases BOD, aquatic life will start flourishing.


Consuming curd keeps the gastro-intestinal tract intact. Give reason.

Curd contains lactic acid bacteria which checks the growth of disease causing microbes and protects the gastro intestinal tract.


Fungi are cosmopolitan. Write the role of fungi in your daily life.

Fungi is a microorganism that is found everywhere. Their presence in nature is important even when few species are harmful. Many plants and trees establish a mycorrhizal relationship with the fungi to survive.
We are very much familiar with yeast as it is widely used for fermentation for thousands of years. They are also used in the production of wine, beer, and bread.
Fungi not only directly produce elements that are used by humans in medicines but also are versatile tools in medical research.
Some fungi attack insects and thus they can be used as natural pesticides.


Why are some microbes useful in detergent formulation?

Some microbes produce enzymes like lipases which help in removing oil stain when used in detergent formulation.


It was observed that certain plant roots are infected by fungus. In spite of this infection the plant showed increased growth and development. Give reason.

The plant roots which are infected by fungi form symbiotic association with them and the fungi help the plant to absorb phosphorus from the soil and also increase drought tolerance in plant thus this symbiotic association called mycorrhiza help in the development of the plant.


(i) Why do farmers prefer biofertilizers to chemical fertilizers these days? Explain.
(ii) How do Anabaena and mycorrhizae act as biofertilizers?

(i) A farmer relies on biofertilizers than chemical fertilizers because:
(a) Chemical fertilizers significantly increase soil pollution and reduce the quality of soil, as well as water pollution, when it drains into nearby water bodies, after rain.
(b) Overuse of chemical fertilizer makes the soil infertile.

(ii)Anabaena fix atmospheric nitrogen, thus enriching the nitrogen content of the soil, as well as the organic matter.
In mycorrhizae, the fungal symbiont absorbs phosphorus from the soil and passes it to the plant and provides resistance to root-borne diseases, Since, they fulfill the nitrogen and phosphorus requirement they act as biofertilizers.


Explain how Rhizobia are useful for farmers.

Answer:
  • Rhizobium is a soil bacteria that aids in nitrogen fixation in leguminous plants. 
  • This bacterium infects the roots of the leguminous plant and forms nodules. 
  • These nodules fix atmospheric nitrogen and convert it into a form that can be readily used by the plant. 


Bottled juices are clearer compared to homemade juices. Give reason

Bottled juices are clarified by the use of pectinases and proteases.


There are certain processes in relation to a sewage treatment. Pick up the correct set.

  • Primary treatment is the first treatment that is used to remove the particles that are suspended and floating in the sewage. It includes screening to trap the particles. The method of sedimentation is used when the particles are removed and settled by gravity.  Primary treatment is usually the first stage of wastewater treatment. 
  • Secondary treatment removes the dissolved organic matter. This is achieved by microbes that can consume and degrade the organic matter converting it to carbon dioxide, water, and energy for their own growth and reproduction. There are certain chemicals that can be used that can help in concentration and sedimentation. This helps to reduce the amount of BOD of the sewage water. 
  • The tertiary treatment process is the modification of a conventional secondary treatment plant to remove additional phosphorus and nitrogen. There is the use of precipitants and flocculants which help in the removal of the wastes. 
Generally, gelatinous precipitants are used for the removal of the particles. 
Activated sludge refers to floc of microorganisms that are used in the process to break down organic matter into carbon dioxide, water, and other inorganic compounds. Some microbes grow in the water forming mass or flocs and help in the clearing of the water. 
So, the correct answer is option A-3, B-4, C-2, D-1.


Can you describe what happens when milk is converted into curd or yoghurt, from your understanding of proteins?

  • Milk contains a protein called casein.
  • When the curd is added to milk, the lactic acid bacteria present in it causes the coagulation of casein that convert milk into curd.


(a) Why are the fruit juices bought from market clearer as compared to those made at home?
(b) Name the bioactive molecules produced by Trichoderma polysporum and Monascus purpureus.

The fruit juices which are available in the market in bottles are clearer because they are treated with the enzymes - pectinases and proteases. So, they are clearer as compared to those made at home.

Trichoderma polysporum is used to produce cyclosporin A which is an immunosuppressive agent. Monascus purpureus is used to produce statins which are blood cholesterol reducing agents. 



How do methanogens help in producing biogas?

Biogas is a mixture of methane and carbon dioxide. Methanogens produce methane, carbon dioxide and hydrogen gas by anaerobic digestion of cellulosic plant part. Thus, methanogens help in producing biogas.


Write down the application of biofertilizers. Explain the role of cyanobacteria as a biofertilizer.

Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilizers are bacteria, fungi, and cyanobacteria (blue-green algae). The application of biofertilizers are as follows:
  • There is increased mineral and water uptake.
  • Due to the presence of the minerals, there is root development and vegetative growth. 
  • These organisms help in the growth of the plant by nitrogen fixation. 
  • These organisms produce growth hormones and products like vitamin-B complex, Indole acetic acid (IAA) and Gibberellic acids etc.
  • They increase the soil fertility and productivity.
Blue-green algae or cyanobacteria such as Nostoc, Anabaena, possess specialized cells. These cells are called as heterocysts. These are modified cells which are formed from the vegetative cells. These are the sites for N$$_2$$ fixation as it contains nitrogenase enzyme which helps in nitrogen fixation. Anabaena is an algae are present in the Azolla plant and are used in the paddy fields for increasing the nitrogen content of the soil and increasing the yield of rice crops. 


What are biocontrol agents? Mention any two groups of biocontrol agents and their hosts?

The use of microorganisms or biological methods to control plant diseases and pests is called biocontrol. The agents which are used to control the microbes are called biocontrol agents.
Bacteria: Black flies, caterpillars, larvae, wax moths can be controlled by Bacillus thuringiensis.
Fungi: Beauveria bassiana acts as biopesticide for aphids, bugs, mites, white flies etc.


The nodules on the roots of leguminous plant are destroyed. How will it affect the plant? Explain with reason.

The bacterial species are present in the cortical cells of the root of the leguminous plants forming root nodules. This bacterium has the enzyme called as nitrogenase which converts the atmospheric nitrogen to a form which can be used by the plant. If these root nodules are destroyed, then the cells will be killed. This will lower the amount of nitrogen present in the soil and thus, result in the deficiency of nitrogen to the plants. Nitrogen is an important macronutrient for the growth of plants. The deficiency if this nutrient will result in chlorosis and finally death of the plants as important activities like replication are affected. 


Name any two edible varieties of mushrooms. Give nutritional values of these mushrooms.

The two edible varieties of mushrooms are Agaricus bisporus and Lentinula edodes. The mushrooms are rich in protein and low fat content. The protein values range very high. They are also a good source of iron, phosphorus and vitamins. Mushrooms are rich in essential amino acids.


Give the name of that bacterial product which is used as a clot buster.

Streptokinase is the product produced by the bacterium Streptococcus. This is known as clot buster. This chemical helps in removing clots from the blood vessels of patients who have undergone myocardial infarction. This product can also be used to remove the clots in the lungs and arteries. 


Penicillin is obtained from which fungus ? 

Penicillin is an antibiotic which is commonly used for the treatment of various bacterial diseases. These are called as $$\beta$$ lactam antibiotics. This is obtained from Penicillium chrysogenum. This is an antibiotic which is active against the Gram negative bacterium. 


What will be the effect on treatment of sewage if microbes are removed from
it ? Clarify. 

Microbes are responsible for the breakdown of the organic matter in the sewage. If the microbes are removed from the sewage treatment, there will be no breakdown of the organic wastes. The wastes will be present in the treatment plant and the BOD (Biological oxygen demand) will not reduce. 


Which are the bacteria responsible for converting organic acids into methane?

$$\textbf{Solution: }$$ 

$$\bullet$$The methanogenic bacteria are the microorganism which is a type of anaerobic bacteria responsible for converting the organic acids into methane. 

$$\bullet$$These anaerobic bacterial species can perform decomposition in absence of oxygen.

$$\bullet$$The organic acid used or acted by the methanogens is acetic acid. 




Match column I with column II and choose correct option.

Citrus acid is an organic acid produced by the microbial fermentation of a fungus, Aspergillus niger.
Butyric acid is produced from the batch fermentation of Clostridium butylicum.
Saccharomyces cerevisiae is a species of yeast used for the production of ethanol by batch fermentation.
Trichoderma polysporum is a species of fungi used for the production of Cyclosporine A, which is an immunosuppressant medication.
Monascus purpureus is a species of mould used for the production of statins that are useful for lowering blood cholesterol levels.


(a) Give the scientific name of the soil bacterium which produces crystal (Cry) proteins.,  (b) How are these proteins useful in agriculture?,  (c) What do the terms Cry and cry represent?

Bacillus thuringiensis (Bt) is a spore forming bacterium that produces crystals protein (cry proteins), which are toxic to many species of insects. There are thousands of different Bt strains, producing over 200 cry proteins that are active against an extensive range of insects and some other invertebrates. Bt is largely used in agriculture, especially organic farming. Bt is also used in urban aerial spraying programs, and in transgenic crops. Cry proteins are a large family of crystalline toxins produced by Bacillus thuringiensis. Individually, the family members are highly specific, but collectively, they target a diverse range of insects and nematodes.


Write short notes on ,  (a) Mycorrhiza,   (b) Role of VAM in crop improvement,  (c) Rhizobium-legume symbiosis ,  (d) Green manure

(a) A mycorrhiza is a symbiotic association between the fungus and the roots of the vascular host plant.
(b) VAM is a fungus that penetrates the roots of a vascular plant in order to help them to capture nutrients from the soil.
(c) It is a group of soil bacteria that infects the roots of legumes to form root nodules.
(d) Green manuring is plowing under the soil incorporation of any green manure crops while they are green or soon after they flower. Green manures are forage or leguminous crops that grow for their leafy materials needed for soil conservation.



Define the term biofertilizers. How does each of the following serve as a biofertilizer?
 (a) Ectomycorrhizae (b) Rhizobium (C) Azospirillum

Bio-fertilizers are living micro-organisms of bacterial, fungal and algal origin. Bio-fertilizers fix atmospheric nitrogen in the soil and root nodules of legume crops and make it available to the plant. 
(a) Ectomycorrhizae-  They act as bio-fertilizer as they provide nutrient, water and minerals to the host.
(b)Rhizobium- They are nitrogen-fixing bacteria, they fix atmospheric nitrogen in the form of nitrates in the roots.
(c)Azospirillum-  It is the free-living nitrogen-fixing bacteria, these are gram negative.


Explain the scientific reason for growing Azolla pinnata in a rice field.

Rice farmers keep Azolla pinnata in the rice field in their paddies because it generates valuable nitrogen via its symbiotic cyanobacteria.T his plant can be grown in wet soil and then plowed under, generating a good amount of nitrogen-rich fertilizer.



Define the following term :
Antibiotics   

An antibiotic is a type of an antimicrobial substance active against bacteria and is the most important type of an antibacterial agent for fighting against bacterial infections. Antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. Antibiotics are not effective against viruses such as the common cold or influenza. Examples, streptomycin, penicillin etc.


What are antibiotics? Name any two examples.

Explanation:
  • An antibiotic is a medicine that inhibits the growth of microorganisms and destroys it.
  • It was first invented by Alexander Fleming, they fight against harmful diseases and infections. They include a range of powerful drugs. 
  • Examples: Penicillin, Kanamycin.




1.Manure fertilizer,  biofertilizer,  mycorrhiza, diazotrophs,  root nodule, Frankia,  nitrogen fixation
..........  is an Inorganic, or organic compounds rich in plant nutrients.

Manure - It is the natural material which is obtained by decaying plant and animal waste.
Biofertilizer- These are living microorganisms which fix nitrogen bacteria in roots of the plants.
Mycorrhiza- It is a symbiotic association between a fungus and vascular plants.
Diazotrophs- These as bacteria that fix atmospheric nitrogen gas into a more usable form.
Root nodule- These are associated with symbiotic nitrogen fixation which occurs at roots.
Frankia-It is the genus of nitrogen-fixing bacteria which lives in symbiotic form.
Nitrogen-fixation- It is a process in which the atmospheric nitrogen is converted into ammonia.
"Fertilizer is inorganic, or organic compounds rich in plant nutrients'.


Define and explain:
manure fertilizer,  biofertilizer,  mycorrhiza    diazotrophs,  root nodule, Frankia,  nitrogen fixation
.......... Organisms which can bring about soil nutrient enrichment.

Manure - It is the natural material which is obtained by decaying plant and animal waste.
Fertilizer - It is an organic or inorganic compound rich in plant nutrients
Diazotrophs- These as bacteria that fix atmospheric nitrogen gas into a more usable form.
Mycorrhiza - It is a symbiotic relationship between fungal hyphae and roots of higher plants.
Root nodule- These are associated with symbiotic nitrogen fixation which occurs at roots.
Frankia-It is the genus of nitrogen-fixing bacteria which lives in symbiotic form.
Nitrogen-fixation- It is a process in which the atmospheric nitrogen is converted into ammonia.
'Bioferilizer organisms which can bring about soil nutrient enrichment'.


Define and explain
manure fertilizer,  biofertilizer,  mycorrhiza, diazotrophs,  root nodule, Frankia,  nitrogen fixation
.......... Organic substances obtained by the decomposition of animal wastes and plant residues which supply essential elements and humus to the soil.

Fertilizer - It is an organic or inorganic compound rich in plant nutrients
Biofertilizer- These are living microorganisms which fix nitrogen bacteria in roots of the plants.
Diazotrophs- These as bacteria that fix atmospheric nitrogen gas into a more usable form.
Mycorrhiza - It is  a symbiotic relationship between fungal hyphae and roots of higher plants
Root nodule- These are associated with symbiotic nitrogen fixation which occurs at roots.
Frankia-It is the genus of nitrogen-fixing bacteria which lives in symbiotic form.
Nitrogen-fixation- It is a process in which the atmospheric nitrogen is converted into ammonia.
'Manure is an organic substance obtained by the decomposition of animal wastes and plant residues which supply essential elements and humus to the soil'.


Mention the role of cyanobacteria as a biofertilizer.

Biofertilizer help in maintaining of soil habitat and helps in plant growth. Cyanobacteria fix nitrogen in the soil which helps the plant to grow. It has been identified as a rich source in biologically active compounds. They play the role as diazotrophs in the soil. 


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

The enzyme produced by streptococcus bacterium is streptokinase. It is a bioactive molecule.  It is used as a 'clot buster' for removing clots from the blood vessels of patients who have undergone myocardial infraction leading to heart attack.


Mention a product of human welfare obtained with the help of each one of the following microbes.
LAB

LAB( Lactic acid bacteria) is used for the production of curd milk. It is a lactobacillus. It converts sugar to lactic acid. Yogurt is thickened, fermented milk made using a mixture of bacteria.


Describe how biogas is generated from activated sludge. List the components of biogas.

Dung and other organic wastes are converted into a slurry with 90% water.  It is passed on to digester. Facultative anaerobic decomposers change the complex organic substances into simpler ones called monomers. The monomers undergo acidification with the help of fermenting microbes. The various products are changed into methane by methanogens. The biogas thus formed collects in floating gas holder for supply. Spent slurry is collected as sludge for use as manure.

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Name and explain the role of the cells present in cyanobacteria which help in nitrogen fixation ?

Cyanobacteria are photosynthetic bacteria and usually lives in aerobic conditions. They synthesize nitrogenase enzyme (required for nitrogen fixation) which is susceptible to oxidation. Photosynthetic oxygen evolution and nitrogen fixation cannot occur simultaneously in one single cell so they develop heterocysts which are nondividing cells which have lost capacity of oxygenic photosynthesis and which contain the enzyme nitrogenase.


Mention a product of human welfare obtained with the help of the following microbe Propionibacterium sharmanii .

Cheese is a dairy product which is made by separating casein and fat of milk separated from the liquid. 
The bacterium Propionibacterium sharmanii is used to make Swiss cheese which is of high-quality.



Write the names of microbes found in following food materials.
yoghurt, bread, root nodules of leguminous plants, idli,dosa, spoiled potato curry.

The microbes found in the following food materials are:-
1. Yoghurt- Streptococcus thermophilus and Lactobacillus bulgaricus which convert the milk sugar lactose to lactic acid.
2. Bread- Saccharomyces cerevisiae which ferments the sugar to produce alcohol and bubbles of carbon dioxide which makes the bread fluffy.
 3. Root nodules of leguminous plants-  Rhizobium which helps in nitrogen- fixation.
4. Idli /dosa- Saccharomyces cerevisiae and Lactobacillus fermentum are responsible for souring and leavening of the batter.
5. Spoiled ptato curry- Staphylococcus aureus and Bacillus subtilis cause spoilage of potato as they have the abilities to produce enzymes that are capable of degrading the tissues.


Mention a product of human welfare obtained with the help of the following microbe Saccharomyces cerevisiae 

Saccharomyces cerevisiae is also known as bakers yeast. These are available in the form of powder and used in cakes.
This is responsible for the release of carbon dioxide after fermentation. This cause a rise in the products.



Explain biogas plant with a labelled diagram.

  • Biogas or gobar gas is a combustible gas.
  • It is produced through the anaerobic breakdown of waste biomass.
  • The biogas plant consists of the following parts:- 
1) Inlet or charge pit:- for passage of slurry into the digester.
The raw material used is cattle dung, farm refuse, organic waste.
2) Digester:- cylindrical tank which is airtight, above which is present a  floating gas holder of metal with an outlet of gas and pit for removal of sludge.
  • Here the organic wastes get solubilized into simpler substances called monomers (solubilisation).
  • Monomers change to organic acid by fermenting microbes (acidogenesis).
  • Organic acid mostly formed is acetic acid.
  • Methanogens become active and act on components of microbial digestion and form methane gas (methanogenesis).
3) Outlet:- consists of sludge which is used as manure.
  • The methane gas formed in this process is used for cooking and lighting.

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Use of mutant strains has been increased in industrial microbiology.

A Strain is a group of species with one/ more characteristics that distinguish it from other subgroups of the same species of the strain. - each strain is identified by a name, number, or letter. Example:- E.coli Strain K12 

  • Some applications of mutant strains are:
  • Increase the productivity of the enzyme. 
  •  Increasing the permeability of the strain for foreign vectors,
  •  Introducing new genetic properties into the organism by recombinant DNA technology / genetic engineering.


Match the columns:
'A''B'
(1) Vinegar(a) Polylactic acid
(2) Cheese(b) Acetic acid
(c) Fungi

(1) Vinegar-Acetic acid
(2) Cheese-Fungi


How are secondary metabolites useful to human welfare? Give two examples of it.

Metabolites are the intermediates and products of metabolism. A secondary metabolite is not directly involved in those processes but usually has an important ecological function. Examples include antibiotics and pigments. Some antibiotics use primary metabolites as precursors, such as actinomycin which is created from the primary metabolite, tryptophan.

If one wants to make a list of biomolecules, such a list will have thousands of organic compounds including amino acids, sugars etc. These are called primary metabolites.

However, when one analyses plant, fungal and microbial cells, one will see thousands of compounds, eg., alkaloids, flavonoids, rubber, essential oils, antibiotics, colored pigments, scents, gums, spices. These are called secondary metabolites.


State the requirements of Chemiosmosis.

Chemiosmosis is making energy molecules by using a microscopic windmill that turns because of the wind-like flow of ions through it. Mitochondria are the membrane pouches inside of a cell that serves as the powerhouses, producing energy molecules called ATP that power the protein inside the cell.


Which fuels can be obtained by microbial process ? Why is it necessary to increase the use of such fuels?

Natural gases( biogas, ethane, methane) can be obtained from the microbial process.
It is necessary to use or increase this because it is man-made and natural gas so it is eco-friendly as well as cheaper than other fuels and also it is a renewable source and for fuels.


Give scientific reason.
Microbial enzymes are used instead of chemical catalysts in chemical industry.

Microbial catalysts are also known as bio-catalysts. Microbial catalysts are preferred over chemical catalysts for various reasons like: • Lesser byproducts are formed in case of microbial enzymes which means the cost of purification is minimised. 
$$\bullet$$ Microbial enzymes can function at low temperatures, pH and pressure, thus saving the energy. 
$$\bullet$$ Enzymes which are used in these processes can be reused as they do not decompose during these processes. 
$$\bullet$$ Use of enzymes also reduces the amount of environmental pollution. 


What is Bio-gas? Write any four uses.

Biogas is a mixture of gases produced by breakdown of organic matter in the absence of oxygen.

- It can be produced from raw material such as agriculture waste, manure, municipal waste, plant material, 

sewage, green waste or food waste.

Uses- 

(i) Direct combustion

(ii) Generation of electricity.

(iii) Purification and export as compressed gas on liquid form.

(iv) Used for cooking purposes which is easier than cooking with firewood.

(v) Used for plastic moulding process.


Answer the following.

Explain the importance of biopesticides in organic farming.

Biopesticide is a term used for bacterial and fungal toxins which can be used to destroy pests/pathogens/insects and can be directly integrated into the plants. The special characteristics of biopesticide is that they do not harm the plant or other organisms except its target organism. Some of the examples of biopesticides are-
$$\bullet$$ Bacillus thuringiensis (Bt) is used to control butterfly caterpillars. This bacterium is available in sachets as dried spores, which are sprayed on the crops. The spores get into the gut of the larvae and kill it while the other insects remain unperturbed. 
$$\bullet$$ By methods of genetic engineering, the genes of B. thuringiensis responsible for killing the larvae have been incorporated into the plants. Cotton plant with Bt gene incorporated is called Bt-cotton. 
$$\bullet$$ The fungus Trichoderma living in roots of plants acts as a biocontrol agent against several plant pathogens. 
$$\bullet$$ Baculoviruses, particularly genus Nucleopolyhedrovirus are also used as narrow spectrum insecticidal agents. 


Match the pairs.
'A' group'B' group
Rhizobiuma. Food poisoning
Clostridiumb. Nitrogen fixation
Penicilliumc. Bakery products
Yeastd. Production of antibiotics

Answer-
1.Rhizobium- (b) Nitrogen fixation
  • Rhizobium is a nitrogen-fixing bacteria, and they are found in the roots of legume plants.

2.Clostridium- (a) Food poisoning
Clostridium botulinum is a gram-positive bacterium that causes severe food poisoning.

3. Penicillium-(d) Production of antibiotics 
Penicillium is a fungus from which antibiotics that kill bacteria are produced. 

4. Yeast-(c) Bakery products
Yeast is used to prepare fermentation products like bread, cakes, etc


.....source available in limited quantity in nature?
Energy obtained from biological factors is called....?
All those products obtained by the process of photosynthesis are collectively called?
The ..... gas is obtained by the fermentation of organic compounds by Bacteria?
Gobar gas ..... contains % of carbon dioxide.

  1. Nonrenewable source of energy is available in limited quantity in nature.
  2. Bio-Energy is the energy obtained from biological factors.
  3. Biomass is the product obtained as a result of photosynthesis
  4. Bio-gas or Gobar gas is the gas obtained by fermentation of organic compounds by bacteria.
  5. Gobar gas contains 31% carbon dioxide.


Class 12 Medical Biology Extra Questions