MICROBES in human welfare

Question 1

making of curd from milk

Answer 1

Micro-organisms such as Lactobacillus and others
commonly called lactic acid bacteria (LAB) grow in milk and convert it to curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculum or starter contains millions of LAB, which at suitable temperatures multiply, thus converting milk to curd, which also improves its nutritional quality by increasing vitamin B12. In our stomach too, the LAB play a very beneficial role in checking disease-causing microbes

Question 2

baker’s yeast

Answer 2

dough, which is used for making bread, is fermented using Saccharomyces cerevisiae

Question 3

, the large holes in ‘Swiss cheese

Answer 3

are due to

production of a large amount of CO2 by a bacterium named Propionibacterium sharmanii.

Question 4

‘Roquefort cheese

Answer 4

ripened by growing a specific fungi on them, which gives them a particular flavour.

Question 5

antibiotics

Answer 5

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

Question 6

Penicillin

Answer 6

Alexander Fleming while working on Staphylococci
bacteria once observed 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

Question 7

antibiotics treated diseases like

Answer 7

plague, whooping cough , diphtheria and leprosy

Question 8

microbes that produce organic acids

Answer 8

Aspergillus niger (a fungus) of citric acid, Acetobacter
aceti (a bacterium) of acetic acid; Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid

Question 9

ethanol

Answer 9

Yeast (Saccharomyces cerevisiae) is used for the commercial production of ethanol

Question 10

lipases

Answer 10

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

Question 11

bottled fruit juices bought
from the market are clearer as compared to those made at home. This is because the bottled juices are clarified by the use of

Answer 11

pectinases and

proteases.

Question 12

. Streptokinase

Answer 12

produced by the bacterium Streptococcus and
modified by genetic engineering is used as a ‘clot buster’ for removing clots from the blood vessels of patients who have undergone myocardial infarction leading to heart attack

Question 13

cyclosporin A

Answer 13

used as an immunosuppressive agent in organ-transplant patients is produced by
the fungus Trichoderma polysporum

Question 14

Statins

Answer 14

produced by the yeast Monascus purpureus have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible
for synthesis of cholesterol

Question 15

sewage

Answer 15

is treated in sewage treatment plants (STPs)

to make it less polluting.

Question 16

Primary treatment

Answer 16

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

Question 17

Secondary treatment

Answer 17

The 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,While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD

Question 18

BOD

Answer 18

BOD refers to

the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria

Question 19

BOD test

Answer 19

The sewage water is treated till the BOD is reduced. The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water

Question 20

what happens after the bod of water is reduced

Answer 20

the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment. This sediment is called activated sludge.

Question 21

activated sludge

Answer 21

. 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

Question 22

anaerobic sludge digesters

Answer 22

Here, 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 a source of energy as it is inflammable

Question 23

biogas

Answer 23

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

Question 24

methanogens

Answer 24

bacteria, which grow anaerobically on cellulosic material, produce a large amount of methane along with CO2 and H2, eg: Methanobacterium

Question 25

where are methanogens found

Answer 25

These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In the rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle

Question 26

goabr

Answer 26

the excreta (dung) of cattle, commonly called
gobar, is rich in these bacteria. Dung can be used for the generation of biogas, commonly called gobar gas

Question 27

biogas plants

Answer 27

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. The spent slurry is removed through another outlet and may be used as fertiliser. Cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes. So biogas plants are more often built in rural areas

Question 28

biocontrol

Answer 28

Biocontrol refers to the use of biological methods for controlling plant
diseases and pests. In modern society, these problems have been tackled increasingly by the use of chemicals – by use of insecticides and pesticides. These chemicals are toxic and extremely harmful, to human beings and
animals alike, and have been polluting our environment

Question 29

the Ladybird,

and Dragonflies

Answer 29

e useful to get rid of aphids and mosquitoes,

respectively

Question 30

Bacillus

thuringiensis

Answer 30

to control butterfly caterpillars

Question 31

how bt works

Answer 31

. 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

Question 32

Bt-cotton

Answer 32

Because of the development of methods of genetic engineering in the last decade or so, scientists have introduced B. thuringiensis toxin genes into plants. Such plants are resistant to attack by insect pests

Question 33

A biological control being developed for use in the treatment of plant
disease is the

Answer 33

fungus Trichoderma. Trichoderma species are free-living fungi that are very common in root ecosystems. They are effective biocontrol agents of several plant pathogens

Question 34

Baculoviruses

Answer 34

pathogens that attack insects and other arthropods. used as biological control agents are in the genus Nucleopolyhedrovirus. .no negative impacts on plants, mammals, birds, fish or even on non-target insects

Question 35

bacteria as biofertilizers

Answer 35

the nodules on the roots of leguminous plants
formed by the symbiotic association of Rhizobium. These bacteria fix atmospheric nitrogen into organic forms, used by the plant as a nutrient. Other bacteria can fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter), thus enriching the nitrogen content of the soil

Question 36

fungi as biofertilizers

Answer 36

Fungi form symbiotic associations with plants (mycorrhiza), like Glomus fungi. 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, increase in plant growth