Microbes in Human Welfare

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?

Solution:

The curd is one of the best examples for substance which contains microbes. It

contains lactic acid bacteria Lactobacillus. We are able to observe millions of

bacteria in a single drop of curd even under light microscope.

2. Give examples to prove that microbes release gases during metabolism.

Solution:

Release of gases by microbial action can be shown as:

a) During fermentation of the dough for dosa, bread or idli, carbondioxide is

produced and gives puffed appearance.

b) The gobar gas plant is another example where methanogens act on organic

waste and through anaerobic digestion produces gases carbon dioxide and

methane.

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

useful applications.

Solution:

Lactic acid bacteria are found in milk. They multiply in number and helps in the

curdling of milk. They increase vitamin B12 in the curd, which is an essential

nutrient. The lactic acid bacteria present in the human stomach prevent the growth

of harmful bacteria. These are useful in the [production of fermented food products

like cheeses, yogurt and sausage.

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4. Name some traditional Indian foods made of wheat, rice and Bengal gram

(or their products) which involve use of microbes.

Solution:

Wheat:

Product: kulcha, bread, jalebie, cake and bhature.

Rice:

Product: dosa and idli

Bengal gram:

Product: khaman, dhokla and wada.

5. In which way have microbes played a major role in controlling diseases

caused by harmful bacteria?

Solution:

Some of the microbes like bacteria, fungi and molds are used in the production of

antibiotics. Antibiotics are the chemical substances produced from microbes and

used to kill or retard the growth of disease microbes. These are useful in

controlling diseases caused by bacteria like cholera, typhoid, diphtheria etc.

Eg: The fungi penicillium motatum produces pencillin. It acts on the cell wall and

destroys the bacteria. Streptomyces species bacteria produces antibiotics like

streptomycin, erythromycin, tetracycline that targets the protein synthesis in

bacteria.

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

antibiotics.

Solution:

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7. What is sewage? In which way can sewage be harmful to us?

Solution:

Large quantities of waste water which is generating in cities and towns is known as

sewage.

It contains large amounts of organic matter, microbes and human excreta. These

microbes are pathogenic in nature. When this sewage mixes with drinking water

pollutes it and causes diseases like cholera, typhoid, amoebic dycentery. To

prevent this, sewage should treat it in sewage treatment plants, and discharge in to

water bodies like rivers and ponds.

8. What is the key difference between primary and secondary sewage

treatment?

Solution:

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

Solution:

Yes, the microbes can also be used as source of energy. The methanogenic bacteria

are used for the generation of the energy in gobar gas plants.

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The gobar gas plant (Biogas plant) consists of inlet, concrete tank and outlet

through the inlet biological wastes and slurry of dung is sent in to concrete tank. A

floating dome is placed over the slurry.

Methanogenic bacteria which are present in the dung participate in the anaerobic

digestion of the organic matter in sludge digester and produces methane is

inflammable and used as source of energy in cooking and lighting. The remaining

waste shall be removed and used as biofertilizer.

10. Microbes can be used to decrease the use of chemical fertilizers and

pesticides. Explain how this can be accomplished.

Solution:

Using of chemical fertilizers and pesticides is common phenomenon for increasing

crop productivity, but these are causing environmental pollution and showing side

effects on living being.

To reduce the side effects, now a days farmers switched on to Organic forming. In

this process instead of chemicals, using Biofertilizers. Biofertilizers are organisms

that increases the fertility of the soil. The main sources of biofertilizers are

bacteria, fungi and cyanobacteria.

Eg: the symbiotic bacteria Rhizobium living in the root nodules of legumes fixes

atmospheric nitrogen in to ammonia and helps in plant growth. Some of the free

living bacteria like Azospirillium and Azotobacter fixes the atmospheric nitrogen

into soil and enrich the soil. The cyanobacteria like vanabaena, nostoc and

oscillatoris are also helps in fixing of atmospheric nitrogen.

The fungus mycorrhiza shows symbiotic association with plants. It absorbs

phosphorus fro soil and supplies it to the plants. Plants which have this association

show resistance to root borne pathogens and tolerance to salinity and water scarcity

and thereby promotes overall plant growth and development.

When farmers are using pesticides, other living forms also get effected. To prevent

this loss, farmer started introduction of natural predators into fields. They used

dragonflies and lady birds to get rid of aphids and mosquitoes. For another

example, spores of Bacillus thurengenesis bacteria mixed with water and sprayed

on plants, as these spore are taken by caterpillar larvae, the toxin present in the

spores kill them.

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By using techniques og genetic engineering scientists introduced toxic genes of

bacillus thuregesis into plants. These plants show resistance to bvinsect pests.

Eg: Bt cotton. For another example Trichoderma fungus is common in root system

of many plants controls the pathogens effectively.

11. Three water samples namely river water, untreated sewage water and

secondary effluent discharges from a sewage treatment plant were subjected

to BOD test. The samples were labeled 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 water is most polluted? Can you assign the

correct label to each assuming the river water is relatively clean?

Solution:

Biological oxygen demand (BOD) is the measure of the organic pollutants present

in the waste water. Greater BOD indicates the high content of organic waste in the

water.

According to BOD untreated sewage water is more polluted.

1. Sample A contains BOD 20mg/L is the secondary effluent discharged from a

sewage treatment plant.

2. Sample B contains BOD 8mg/L is the river water.

Sample C contains BOD 400mg/L is the untreated sewage water.

12. Find out the name of microbes from which Cyclosporin A (an

immunosupportive drug) and Statins (blood cholesterol lowering agents) are

obtained.

Solution:

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13. Find out the role of microbes in the following and discuss it with your

teacher.

a) Sinngle cell protein (SCP)

b) Soil

Solution:

a) Single cell protein (SCP)

It refers to sources of mixed protein extracted from pure or mixed cultures of algae,

yeasts, fungi or bacteria (grown on agricultural wastes) uses as a substitute for

protein-rich foods, in human and animal feeds.

Microbes employed include yeasts (Saccharomyces cerevisiae, Candida untilis),

other fungi (Aspergillus oryzae, Trichoderma), bacteria (Rhodopseudomonas

capsulate, Methylophilus methylotrophus) and algae (chorella and Spirulina

maxima). It serves as a rich supplement of dietary nutrients to conventional food.

b) Soil

Soil contains number of microbes, these helps in the maintaining fertility of the

soil.

Eg:

1. Rhizobium is found in thr root nodules of legumes shows symbiotic association

and fix atmospheric nitrogen.

2. Some of the free living bacteria like Azotobacter and Azospirillum fixes the

atmospheric nitrogen and enrich the soil.

3. Fungi Mycorrhiza shows symbiotic association with plants, these absorb

phosphorus and pass it into the plants.

4. Cyanobacteria like nostoc, anabena, oscillatoria shows symbiotic association

and fix atmospheric nitrogen in aquatic and terrestrial habitats.

14. 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. Panocollin and Curd

Solution:

The products in the decreasing order of their importance are as follows:

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Penicillin – Biogas – Curd – Citric acid

1. Penicillin is an antibiotic obtained from fungi Penicillium notatum. It is the most

important product for the welfare of human society for its role in controlling a

number of infectious diseases.

2. Clean energy is the most important requirement of the mankind. As biogas is

eco-friendly source of energy, it is the need of the hour to use more and more such

form of energy.

3. Curd is a part of our daily diet. It’s a food item cobatin by the action of

lactobacillus bacteria on milk, which provides proteins, carbohydrates and vitamin

B12.

4. The last important is citric acid which helps in preservation of different types of

food items.

15. How do biofertilizers enrich the fertility of the sooil?

Solution:

Bio-fertilizers are living organisms and they increase the fertility of the soil

through nitrogen fixation. Rhizobium is a symbiotic bacteria found in the root

nodules of leguminous plants. They fix atmospheric nitrogen and eventually enrich

the soil through the root nodules. Similarly, Azospirillium and Azotobacter are free

living nitrogen-fixing bacteria, whereas Anabena, Nostoc and Oscillatoria are

examples of nitrogen-fixing cyanobacteria. Both of them fixes the atmospheric

nitrogen in the form of nitrates and enrich the soil. Fungus Micorrhiza shows

symbiotic association with roots of higher plants like eucalyptus, oaks and they

absorb phosphorous and pass it on to the plants

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