Microbes in Human Welfare
Microbes like bacteria and many fungi can be grown on nutritive media to form colonies, that can be seen with the naked eyes. Such cultures are useful in studies on micro-organisms.
10.1 Microbes in Household Products10.2 Microbes in Industrial Products10.3 Microbes in Sewage Treatment10.4 Microbes in Production of Biogas10.5 Microbes as Biocontrol Agents10.6 Microbes as Biofertilisers
- Lactobacillus or 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 contain millions of LAB, at suitable temperatures multiply, thus converting milk to curd, improves its nutritional quality by increasing vitamin B12
- Human stomach LAB play very beneficial role in checking disease- causing microbes
- The dough, used for making foods such as dosa and idli is fermented by bacteria, puffed-up appearance of dough is due to the production of CO2 gas
- the dough, used for making bread, is fermented using baker’s yeast (Saccharomyces cerevisiae)
- Traditional drinks and foods made by fermentation by the microbes
- ‘Toddy’, a traditional drink of some parts of southern India is made by fermenting sap from palms
- Microbes used to ferment fish, soyabean and bamboo-shoots to make foods
- Cheese, varieties of cheese of characteristic texture, flavour and taste, the specificity coming from the microbes used
- The large holes in ‘Swiss cheese’ are due to production of a large amount of CO2 by a bacterium Propionibacterium sharmanii
- The ‘Roquefort cheese’ ripened by growing a specific fungi on them, which gives them a particular flavour.
MICROBES IN INDUSTRIAL PRODUCTS
Even in industry, microbes are used to synthesise a number of products valuable to human beings. Beverages and antibiotics are some examples.
Production on an industrial scale, requires growing microbes in very large
vessels called fermentors
Biochemical oxygen demand - the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
- BOD test is a measures the rate of uptake of oxygen by micro-organisms in a sample of water
- BOD is a measure of the organic matter present in the water
- Greater BOD, more polluted water
Microbes in sewage treatment: -
- Waste water also with human excreta is generated everyday called sewage and contains organic matter and microbes mostly pathogenic
- This water cannot be discharged directly and needs to be treated before
- Treatment is carried out in two stages: - (i) Primary Treatment and (ii) Secondary Treatment
- Primary Treatment: -
- Physical removal of particles - large and small - through filtration and sedimentation.
- Floating debris by sequential filtration, grit (soil and small pebbles) removed by sedimentation
- Solids settled form primary sludge and supernatant forms effluent and taken to secondary treatment
- Secondary Treatment (Biological Treatment) -
- Effluent is passed into large aeration tanks, agitated mechanically and air is pumped into it
- Vigorous growth of useful microbes into flocs (masses of bacteria associated with fungal filaments to form mesh like structure) takes place
- Microbes consume organic matter while growing and reduces biochemical oxygen demand
- BOD test is a measures the rate of uptake of oxygen by micro-organisms in a sample of water
- BOD is a measure of the organic matter present in the water
- Greater the BOD of waste water, more is its polluting potential
- After BOD reduced, effluent passed into settling tank to make flocs sediment (activated sludge)
- Small activated sludge pumped back to aeration tank to serve as inoculum
- Major part of sludge pumped to large tanks called anaerobic sludge digesters
- Here other kind of bacteria grows anaerobically, digesting bacteria and fungi of sludge.
- During digestion mixture of gases called biogas viz methane, hydrogen sulphide and carbon dioxide is produced
Effluent from secondary treatment plant is released into natural water bodies like rivers and streams
Microbes in production of biogas: -
Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel.
- microbes produce different types of gaseous end-products during growth and metabolism. The type of the gas produced depends upon the microbes and the organic substrates they utilise. In the examples cited in
relation to fermentation of dough, cheese making and production of beverages, the main gas produced was CO2..
- Bacteria growing anaerobically on cellulosic material, produce large amount of methane along with CO2 and H2. 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. 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 rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.
- The excreta (dung) of cattle, commonly called gobar, is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas.
Biogas plant: -
-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 after build in rural areas. The biogas thus produced is used for cooking and lighting.
-The technology of biogas production was developed in India mainly due to the efforts of Indian Agricultural Research Institute (IARI) and Khadi and Village Industries Commission (KVIC).
Microbes as biocontrol agents: -
Biocontrol refers use of biological methods to control plant diseases and pests.
- Plant disease and pests tackled by chemicals – insecticides and pesticides.
- Chemicals are toxic and extremely harmful, to human beings and animals alike, and pollute environment (soil, ground water), fruits, vegetables and crop plants
- Weedicides to remove weeds but pollutes soil
- Biological control of pests and diseases includes method of controlling pests that relies on natural predation rather than use of chemicals,
- Biodiversity furthers health and the more variety a landscape has, the more sustainable it is
- Organic farming is not eradicating insects or pests but keeping at manageable levels by a complex system of checks and balances within a living and vibrant ecosystem.
- this is a holistic approach that seeks to develop an understanding of the webs of interaction between the myriad of organisms that constitute the field fauna and flora
- The organic farming mentions that eradication of the creatures or 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
- Use of biocontrol measures reduces dependence on toxic chemicals and pesticides
- biological farming approach is to become familiar with the various life forms that inhabit the field, predators as well as pests, and also their life cycles, patterns of feeding and the habitats that they prefer
- The very familiar beetle with red and black markings – the Ladybird, and Dragonflies are useful to get rid of aphids and mosquitoes,
- The bacteria Bacillus thuringiensis (often written as Bt) is a microbial biocontrol agents introduced in order to control butterfly caterpillars
- 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.
- Introduction of B. thuringiensis toxin genes into plants led plants to resistant to attack by insect pests
- Bt-cotton is one such example, which is being cultivated in some states of our country.
- Fungus Trichoderma is a biological control agent for treatment of plant disease
- Trichoderma, a free-living fungi, very common in the root ecosystems, are effective biocontrol agents of several plant pathogens
- Baculoviruses are pathogens that attack insects and arthropods
- Majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus.
- These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications, no negative impacts on plants, mammals, birds, fish or even on non-target insects
- This is especially desirable when beneficial insects are being conserved to aid in an overall integrated pest management (IPM) programme, or when an ecologically sensitive area is being treated.
Microbes as biofertilisers: -
- Biofertilisers are organisms that enrich the nutrient quality of the soil
- The main sources of biofertilisers are bacteria, fungi and cyanobacteria
- nodules on the roots of leguminous plants formed by the symbiotic association of Rhizobium
- These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as 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
- Fungi form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza, symbiont associations absorbs phosphorus from soil and passes it to the plant, such associations show resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.
- Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria
- In paddy fields, cyanobacteria / blue green algae add organic matter to the soil and increase its fertility
MCQs
1. Conversion of Milk to curd improves its nutritional value by increasing the amount of
a. Vitamin D, b. Vitamin A, c. Vitamin B12, d. Vitamin E
Ans. c. Vitamin B12
2. Dough kept overnight in warm weather becomes soft and spongy because of
a. absorption of CO2 from atmosphere, b. fermentation, c. cohesion, d. osmosis
Ans. a.
3. During the formation of bread it becomes porous due to release of CO2 by the action of
a. yeast, b. bacteria, c. virus, d. protozoans
Ans. a. yeast
4. In cheese manufacture, the microorganisms are important for
a. the ripening only, b. the souring of milk only, c. the development of resistance to spoilage only, d. both the souring and the ripening processes
Ans. d. both the souring and the ripening processes
5. Match the following columns and select the correct option
----Column I----------------------------Column -II
A Clostridium butylicum ----------(i) Cyclosporin-A
B Trichoderma polysporum ------(ii) Butyric Acid
C. Monascus purpureus -----------(iii) Citric acid
D Aspergillus niger -----------------(iv) Blood cholestrol lowering agent
a. A-iii, B-iv, C-ii, D-i
b. A-ii, B-i, C-iv, D-iii
c. A-i, B-ii, C-iv, D-iii
d. A-iv, B-iii, C-ii, D-i
Ans. b. A-ii, B-i, C-iv, D-iii
6. Which of the following is a commercial blood cholesterol lowering agent?
a. Lipases, b. Cyclosporin A, C. statin, d. Streptokinase
Ans. C. Statins
7. Match the following organisms with the products they produce
A. Lactobacillus -------------------(i) Cheese
B. Saccharomyces cerevisae ----(ii) Curd
C. Aspergillus niger --------------(iii) Citric acid
D. Acetobacter aceti --------------(iv) Bread, (v) Acetic acid
a. A-ii, B-i, C-iii, D-v
b. A-ii, B-iv, C-v, D-iii
c. A-ii, B-iv, C-iii, D-v
d. A-iii, B-iv, C-v, D-i
Ans. c.
8. Which of the following is correctly matched for the product produced by them?
a. Methanobacterium : Lactic acid
b. Penicillium notatum : Acetic acid
c. Sacchromyces cerevisiae : Ethanol
d. Acetobacter aceti : Antibiotics
Ans. c. Sacchromyces cerevisiae : Ethanol
9. Match the column I with Column II and select the correct option using the codes given below:
---------Column I-------------Column II
A. Citric acid -------------(i) Trichoderma
B. Cyclosporin A---------(ii) Clostridium
C. Statins ------------------(iii) Aspergillus
D. Butyric acid ----------(iv) Monascus
a. A-iii, B-i, C-ii, D-iv
b. A-iii, B-i, C-iv, D-ii
c. A-i, B-iv, C-ii, D-iii
d. A-iii, B-iv, C-i, D-ii
Ans. b. A-iii, B-i, C-iv, D-ii
10. Which of the following is wrongly matched in the given table?
-----Microbe--------------------------Product---------------Application
a. Streptococcus ------- ------------Streptokinase ------ Removal of clot from blood vessel
b. Clostridium butylicum -------Lipase ---------------- Removal of oil stains
c. Trichoderma polysporum ----Cyclosporin A----Immuno-suppressive drung
d. Monascus purpureus ----------Statins -------------- Lowering of blood cholesterol
Ans. b.