1 Microbes in Household Products

2 Microbes in Industrial Products

13 Microbes in Sewage Treatment

4 Microbes in Production of Biogas

5 Microbes as Biocontrol Agents

6 Microbes as Biofertilisers

Microbes are present everywhere –in soil, water, air, inside our bodies and that of other animals and plants. True or False

Ans. True

Microbes are present only in favorable conditions. Comment

Ans. NO. Microbes  are present even at places where no other life-form could possibly survive– sites such as deep inside the geysers (thermal vents) where the temperature may be as high as 1000C, deep in the soil, under the layers of snow several metres thick, and in highly acidic environments.

Microbes include

1. Protozoa
2. Bacteria
3. Fungi
4. Viruses, viroids and prions
5. All

Ans. 5) All

Draw a well labeled diagram of a bacteriophage.

Ans.

Adenovirus which causes

1. Respiratory infections
2. Skin infection
3. Circulatory problems
4. All

Ans. Respiratory infections

Mosaic Virus (TMV) is

1. Polyhedral
2. Spherical
3. Rod-shaped
4. Complex

Ans. 3) Rod-shaped

181 Rod-shaped Tobacco

Which of the following is FALSE?

1. Microbes cause a large number of diseases in human beings.
2. Microbes cause diseases in animals and plants. \
3. All microbes are harmful
4. Several microbes are useful to man

Ans. All microbes are harmful

What is the full form of LAB?

Ans. Lactic Acid Bacteria

Name the organism which converts milk into curd.

Ans. Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria (LAB)grow in milk and convert it to curd.

How curd is prepared?

Ans. To prepared curd, a small amount of curd added to the fresh milk as inoculum or starter containing millions of LAB, which at suitable temperatures multiply, thus converting milk to curd.

Mention some useful applications of LAB besides converting milk to curd.

Ans. Some useful applications of LAB are:

1. During growth, the LAB produce acids that coagulate and partially digest the milk proteins.
2. Improves nutritional quality by increasing vitamin B12.
3. In our stomach, the LAB play very beneficial role in checking disease causing microbes.

How dough, which is used for making foods such as dosa and idli, is prepared?

Ans. The dough, which is used for making foods such as dosa and idli is fermented by bacteria.

Mention the reason for the puffed-up appearance of dough.

Ans. The puffed-up appearance of dough is due to the production of CO2 gas.

How the dough, which is used for making bread, is prepared?

Ans. The dough, which is used for making bread, is fermented using baker’s yeast (Saccharomyces cerevisiae).

A number of traditional drinks and foods are made by _________________________.

Ans.fermentation by the microbes

What is “Toddy”?

Ans. ‘Toddy’ is a traditional drink of some parts of southern India.

How toddy is made?

Ans. ‘Toddy’ is made by fermenting sap from palms.

Microbes are also used to __________fish, soyabean and bambooshoots to make foods.

Ans. ferment

Why there are large holes in ‘Swiss cheese’?

Ans. The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium

Name the bacterium which produces  in ‘Swiss cheese’.

Ans. Propionibacterium sharmanii

How are ‘Roquefort cheese’ are ripened?

Ans. The ‘Roquefort cheese’ are ripened by growing a specific fungi on them, which gives them a particular flavour.

10.2 MICROBES IN INDUSTRIAL PRODUCTS

Give example of two products produced by microbes?

Ans. Beverages and antibiotics

What are fermentors?

Ans. Fermentors are very large vessels in which microbes are grown to produce valuable products on an industrial scale.

Name the yeast used for the production of beverages like wine, beer, whisky, brandy or rum.

Ans.  Saccharomyces cerevisiae, commonly called Brewer’s yeast

Which of the following is true?

1. Wine and beer are produced without distillation
2. Whisky, brandy and rum are produced by distillation
3. Whisky, brandy and rum are produced without distillation
4. Both (1) & (2)

Ans. 4) Both (1) & (2)

Write a short note on “Fermented Beverages”.

Ans. Microbes particularly yeasts have been used from time immemorial for the production of beverages like wine, beer, whisky, brandy or rum. The yeast Saccharomyces cerevisiae used for bread-making and commonly called brewer’s yeast is used for fermenting malted cereals and fruit juices, to produce ethanol.

Depending on the type of the raw material used for fermentation and the type of processing (with or without distillation) different types of alcoholic drinks are obtained. Wine and beer are produced without distillation whereas whisky, brandy and rum are produced by distillation of the fermented broth.

What are antibiotics?

Ans. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.

Antibiotics have significantly improved our ability to treat deadly diseases such as plague, whooping cough (kali khansi), diphtheria (gal ghotu) and leprosy (kusht rog).

Name the first antibiotic.

Ans. Penicillin.

Name the scientist who discovered Penicillin.

Ans. Alexander Fleming

How did Alexander Fleming discover Penicillin?

Ans. Discovery of  Penicillin is an example of chance discovery (serendipity). Alexander Fleming while working on Staphylococci bacteria, once observed that a mould growing in one of his unwashed culture plates around which Staphylococci could not grow. He found out that it was due to a chemical produced by the mould and he named it Penicillin after the mould Penicillium notatum.

Name the source of Penicillin.

Ans. Penicillium notatum (also known as Penicillium Chrysogenum)

Name the scientists who established full potential of penicillin as an effective antibiotic.

Ans. Ernest Chain and Howard Florey

Name some antibiotics and also mention their sources.

Ans. Some antibiotics with their sources:

Name of antibiotics	Source organism
Penicillin	Penicillium notatum (also known as Penicillium Chrysogenum)
Streptomycin	Streptomyces griseus
Tetracycline	Streptomyces rimosus
Gentamicin	Micromonospora purpurea
Griseofulvin	Penicillium griseofulvum

10.2.3 Chemicals, Enzymes and other Bioactive Molecules

Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes. True/ False

Ans. True

Which of the following are acid producers?

1. Aspergillus niger
2. Acetobacter aceti
3. Clostridium butylicum
4. Lactobacillus
5. All

Ans. 5) All

Name the microbe which produces citric acid.

Ans. Aspergillus niger (a fungus)

Name the microbe which produces acetic acid.

Ans. Acetobacter aceti (a bacterium)

Name the microbe which produces acetic acid.

Ans. Clostridium butylicum (a bacterium)

Name the microbe which produces lactic acid.

Ans. Lactobacillus (a bacterium)

Name the yeast used for commercial production of ethanol.

Ans. Saccharomyces cerevisiae

Name the enzymes used in detergent formulations.

Ans. Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry.

Bottled fruit juices bought from the market are clearer as compared to those made at home. Why?

Ans. This is because the bottled juices are clarified by the use of enzymes pectinases and proteases.

Name the bacterium which produces Streptokinase.

Ans. Streptococcus

Mention the function of Streptokinase.

Ans. Streptokinase is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infaction leading to heart attack.

Name the organism which produces cyclosporin A.

Ans. Cyclosporin A is produced by the fungus Trichoderma polysporum.

What is cyclosporin A?

Ans. Cyclosporin A is bioactive molecule, which is used as an immunosuppressive agent in organ-transplant patients.

Name the organism which produces Statins.

Ans. Statins are produced by the yeast called Monascus.

What are Statins?

Ans. Statins are a class of drugs that acts as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

10.3 MICROBES IN SEWAGE TREATMENT

Why is sewage treated before disposal?

Ans. Sewage also called municipal waste-water contains large amounts of organic matter, human excreta and microbes. Many microbes are pathogenic in nature. If sewage is discharged directly into natural water bodies like rivers and streams directly, it will cause pollution and health hazards. Therefore, sewage is treated in sewage treatment plants (STPs) to make it less polluting.

Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage.  True/False

Ans. True

Name the two stages of sewage treatment.

Ans. Sewage treatment is carried out in two stages:

1. Primary Treatment
2. Secondary Treatment or Biological Treatment

Briefly describe primary treatment of sewage.

Ans. Primary treatment steps mainly involve physical removal of particles – large and small – from the sewage through filtration and sedimentation. Substances present in sewage are removed in stages; initially, floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge, and the supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.

Describe secondary treatment of sewage.

Ans. Secondary treatment of sewage takes place as follows:

The primary effluent is passed into large aeration tanks where it is continuously 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 (biochemical oxygen demand) of the effluent. The sewage water is treated till the BOD is reduced.

Once the BOD of sewage or waste water is decreased significantly, 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 the 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.

In anaerobic sludge digesters, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge.  During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable.

The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams. In this way water is recycled in nature.

What is the full form of BOD?

Ans. Biochemical Oxygen Demand

Define BOD.

Ans. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.

What is the significance of BOD Test?

Ans. BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, indirectly, BOD is a gauge of the organic matter present in the water. The greater the BOD of waste water, more is the organic matter present in waste water, more is its polluting potential.

What is activated sludge?

Ans. Activated sludge refers to aerated sewage containing aerobic microorganisms which helps to break it down.

What are the initiatives taken by the government of India to save major rivers from pollution?

Ans. The Ministry of Environment and Forests has initiated the following two plans to save our rivers from pollution:

1. Ganga Action Plan
2. Yamuna Action Plan

Under these plans, it has been proposed to build a large number of sewage treatment plants so that only treated sewage may be discharged in the rivers.

10.4 MICROBES IN PRODUCTION OF BIOGAS

What is biogas?

Ans. Biogas is a mixture of gases (containing mainly methane) produced by the microbial activity and which may be used as fuel.

What are the factors that determine the type of the gas produced by microbes?

Ans. Microbes produce different types of gaseous end-products during growth and metabolism.

The type of the gas produced depends upon

1. The microbes
2. The organic substrates

Name the main gas produce in fermentation of dough, cheese making and production of beverages?

Ans.

What are methanogens?

Ans. Methanogens are bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with and .

Give an example of methanogens.

Ans. Methanobacterium.

Which of the following statement is true about methanogens?

1. These bacteria are commonly found in the anaerobic sludge during sewage treatment.
2. These bacteria are also present in the rumen (a part of stomach) of cattle.
3. Both (1) & (2)
4. None

Ans. Both (1) & (2)

What is the role of methanogens in the rumen of cattle?

Ans. The food of cattle contains a large amount of cellulosic material. In rumen, these bacteria assist in the breakdown of cellulose and play an important role in the nutrition of cattle.

Are human beings able to digest the celluose present in our foods?

Ans.  Human beings cannot digest cellulose. This is because they lack the enzymes required  to breakdown cellulose.

Draw a well labelled diagram of biogas plant. Explain its working.

Ans. The excreta (dung) of cattle, gobar, is rich in methanogens. Dung can be used for production of biogas, commonly called gobar gas.

The biogas plant consists of a 10-15 feet deep concrete tank called digester. Bio-wastes are collected fed into the digester as slurry of dung. A floating cover, called gas-holder, 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. The biogas so produced is used for cooking and lighting.

The spent slurry is removed through another outlet and may be used as fertiliser.

Name the institutions responsible for developing technology of biogas production in India?

Ans. The technology of biogas production was developed in India mainly due to the efforts of

1. Indian Agricultural Research Institute (IARI)
2. Khadi and Village Industries Commission (KVIC)

10.5 MICROBES AS BIOCONTROL AGENTS

What do you mean by Biocontrol?

Ans.Biocontrol refers to the use of biological methods and biological agents for controlling plant diseases and pests.

Biological control of pests and diseases:

• In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals.

Which of the following is true?

1. Biodiversity fosters health of the ecosystem
2. The more variety a landscape has, the more sustainable it is.
3. Both (1) & (2)
4. None

Ans. 3) Both (1) & (2)

Write a short note on organic farming. How is it different from ‘conventional’ farming?

Ans. Organic farming is a form of agriculture that relies on techniques such as crop rotation, green manure, compost, and biological pest control.

In organic farming, the emphasis is on developing an understanding of the webs of interaction between the myriad of organisms that constitute the field fauna and flora; and creating a system where pests are not eradicated, but are kept at manageable levels by a complex system of checks and balances within a dynamic ecosystem.

The organic farming believes that the eradication of the creatures that are often described as pests is not only possible, but also undesirable, for without them the beneficial predatory and parasitic insects which depend upon them as food or hosts would not be able to survive.

In contrast, the ‘conventional’ farming practices use chemical methods to kill both useful and harmful life forms indiscriminately.

The use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides. True/False

Ans. True

Which of the following is true?

1. Ladybird is useful in controlling aphids
2. Dragonflies are useful to get rid of mosquitoes
3. Both (1) & (2)
4. None

Ans. 3) Both (1) & (2)

Give an example of microbial biocontrol agent that can be introduced in order to control butterfly caterpillars.

Ans. Bacillus thuringiensis (often written as Bt).

Write a short note on Bacillus thuringiensis.

Ans. Bacillus thuringiensis is an excellent example of microbial biocontrol agent. These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed. The bacterial disease will kill the caterpillars, but leave other insects unharmed.

The development of methods of genetic engineering has allowed us to introduce B. thuringiensis toxin genes into plants, making them resistant to attack by insect pests.

Give one example of pest resistant plant.

Ans. Bt-cotton

Name the fungus which is used in treatment of plant diseases and serves as biocontrol agents of several plant pathogens.

Ans.Trichoderma.

Which of the following is true?

1. Trichoderma species are free-living fungi
2. They are very common in the root ecosystems
3. Both (1) & (2)
4. None

Ans. Both (1) & (2)

What are Baculoviruses?

Ans. Baculoviruses are pathogens that attack insects and other arthropods.

Name the genus that contains majority of baculoviruses used as biological control?

Ans. Nucleopolyhedrovirus.

What are the advantages of Baculoviruses?

Ans. Advantages of Baculoviruses are:

1. Baculoviruses are excellent agent for species-specific, narrow spectrum insecticidal applications.
2. They do not have negative effects on plants, mammals, birds, and fish or even on non-target insects.
3. They play an important role in integrated pest management (IPM) programme, especially when beneficial insects are to be conserved or when an ecologically sensitive area is being treated.

10.6 MICROBES AS BIOFERTILISERS

How can we deal with pollution caused by the use of chemical fertilisers?

Ans. Pollution caused by the use of chemical fertilisers can be dealt by switching to organicfarming – the use of biofertilisers.

What do you mean by Biofertilisers?

Ans. Biofertilisers refer to a substance which contains organisms that enrich the nutrient quality of the soil.

What are the main sources of biofertilisers?

Ans. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

 What are root nodules?

Ans. These are nodules found on the roots of leguminous plants formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, enriching the nitrogen content of the soil, which is used by the plant as nutrient,

Name two bacteria free-living in the soil that fix nitrogen.

Ans. Azospirillum and Azotobacter

Briefly explain mycorrhiza?

Ans. Mycorrhiza is a symbiotic association between fungi and roots of a vascular plant. Many members of the genus Glomus form mycorrhiza.

            In this mycorrhizal association, the fungal symbiont absorbs phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.  

What advantage the fungus derives from mycorrhizal association?

Ans. In mycorrhizal association, the plants supply nutrients (carbohydrates, vitamins, etc), growth stimulators, etc for fungus.

Give examples of Cyanobacteria which fix atmospheric nitrogen.

Ans. Anabaena, Nostoc, Oscillatoria, etc

Briefly describe Cyanobacteria Biofertilizers.

Ans. 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.

Microbes are an insignificant component of life on earth. True/False

Ans. False

All microbes are pathogenic. True/False

Ans. False

The dough, which is used to make bread, is fermented by yeast called ______________

Ans. Saccharomyces cerevisiae

EXERCISES

1. Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?
2. Give examples to prove that microbes release gases during metabolism.
3.  In which food would you find lactic acid bacteria? Mention some of their useful applications.
4. Name some traditional Indian foods made of wheat, rice and Bengal gram (or their products) which involve use of microbes.
5.  In which way have microbes played a major role in controlling diseases caused by harmful bacteria?
6.  Name any two species of fungus, which are used in the production of the antibiotics.
7. What is sewage? In which way can sewage be harmful to us?
8. What is the key difference between primary and secondary sewage treatment?
9. Do you think microbes can also be used as source of energy? If yes, how?
10.  Microbes can be used to decrease the use of chemical fertilisers and pesticides. Explain how this can be accomplished.
11. Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?
12. Find out the name of the microbes from which Cyclosporin A (an immunosuppressive drug) and Statins (blood cholesterol lowering agents) are obtained.
13. Find out the role of microbes in the following and discuss it with your teacher.

(a) Single cell protein (SCP)

(b) Soil

1.  Arrange the following in the decreasing order (most important first) of their importance, for the welfare of human society. Give reasons for your answer. Biogas, Citric acid, Penicillin and Curd
2. How do biofertilisers enrich the fertility of the soil?

D’S