Biology - Microbes in Human Welfare Important Questions
Short Questions
1. How Lactic acid bacteria improve the nutritional quality of milk?
Answer : LAB improves the nutritional quality of milk by increasing Vitamin B12.
2. Explain how a small amount of curd added to milk convert milk into curd?
Answer: A small amount of curd added to the milk contain millions of Lactic Acid Bacteria (LAB) , which at suitable temperature multiply, thus converting milk to curd. During growth, LAB produce acids that coagulate and partially digest the milk proteins.
3. Name the microorganisms used for making
i) Bread
ii) Swiss cheese
iii) cyclosporin A
iv) Statins
v) Citric acid
Answer: i) Saccharomyces cerevisiae
ii) Propionibacterium sharmanii
iii) Trichoderma polysporum
iv) Streptococcus
v) Aspergillus niger
4. What's the medical use of Streptokinase?
Answer: Streptokinase is used as 'Clot Buster' for removing clots from blood vessels of patients who have undergone myocardial infarction leading to heart attack.
5. What's the medical use of Cyclosporin A?
Answer: Cyclosporin A is used as an immunosuppressive agent in organ-transplant patients.
6. What's the medical use of Statins?
Answer: Statins are blood cholesterol lowering agents.
7. The complete potential of Penicillin was established by?
Answer: Ernst Chain and Howard Florey.
8. Secondary treatment of the sewage is also called Biological Treatment. Explain why?
Answer: The secondary treatment of sewage is also called biological treatment because during this step, dissolved orgainc matter is removed with the help of biological agents(such as bacteria and fungi). While growth, these microbes consume the major part of organic matter in the effluent.
9. What is BOD?
Answer: BOD ( Biochemical Oxygen Demand) refers to the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidized by bacteria.
Indirectly, BOD is a measure of the organic matter present in the water. The greater the BOD of Waste water, more is its polluting potential.
10. Name the gases produced during Biogas production.
Answer: Methane, Hydrogen Sulphide and Carbon dioxide.
11. What are biofertilisers?
Answer: Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are Bacteria, Fungi and Cyanobacteria.
12. Name Two alcoholic drinks produced:
a) without Distillation
b) by Distillation
Answer: a) Wine and Beer are produced without distillation.
b) Brandy and Whisky are produced by distillation of fermented broth.
13. The BOD of three water samples A, B and C are 12, 0.3 and 78 respectively. Which sample is most and least polluted?
Answer: Sample C is most polluted. Sample B is least polluted. "The greater the BOD, more is the polluting potential. "
Long Question
1. Describe the procedure involved in sewage treatment.
Answer: Treatment of waste water is done by the heterotrophic microbes naturally present in the sewage. This treatment is carried out in two stages:
Primary treatment : These treatment steps basically involve physical removal of particles – large and small – from the sewage through filtration and sedimentation. These 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.
Secondary treatment or Biological treatment : 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 (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. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidised by bacteria. 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 and thus, indirectly, BOD is a measure of the organic matter present in the water. The greater the BOD of waste water, more is its polluting potential. Once the BOD of sewage or waste water is reduced 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. 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 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.
2. What are Biofertilisers? How does Fungi and Cyanobacteria acts as biofertilisers?
Answer: Biofertilisers are organisms that enrich the nutrient quality of the soil. The main source of biofertilisers are Bacteria, Fungi and Cyanobacteria.
Fungi as Biofertilisers : Fungi form symbiotic association with plants (mycorrhiza) . Many members of Genus Glomus form mycorrhiza. The fungal symbiont in this association absorbs phosphorus from soil and passes it to the plants. Plants having such association show other benefits like Resistance to root borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.
Cyanobacteria as biofertilisers: 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.