Microbes in Human Welfare
Short Questions and Answers
One mark questions with answers
1. Which of the following can be controlled by using biopesticides?
(d) all of them
Answer: (d) all of them
2. Single cell protein represents
(a) protein extracted from a microorganism
(b) protein from a clone of cells
(c) protein mass from single cell animals
(d) biomass from growth of a microorganism
Answer: (d) biomass from growth of a microorganism
3. Yeast is used in preparation of
(a) acetic acid
(c) ethyl alcohol
Answer: (c) ethyl alcohol
4. Scientist first to isolate streptomycin was
Answer: (d) Waksman
5. Penicillin was discovered by
Answer: (a) Fleming
6. The first antibiotic to be isolated was
Answer: (d) Penicillin
7. Leavened bread is produced with the help of
Answer: (a) yeast
8. Germinating barley seeds are used in preparation of
(a) lactic acid
Answer: (d) beer
9. First bioinsecticide developed commercially was
Answer: (a) Sporeine
10. Sporeine was first commercially produced in
Answer: (d) Germany
11. Organic acid first produced through fermentation is
(a) propionic acid
(b) lactic acid
(c) citric acid
(d) oxalic acid
Answer: (b) lactic acid
12. Cheese and yogurt are products of
Answer: (b) fermentation
13. Vinegar is prepared from alcohol with the help of
Answer: (b) Acetobacter
14. Rennin employed in cheese industries is
Answer: (c) enzyme
15. Penicillin inhibits bacterial multiplication because it
(a) checks RNA synthesis
(b) checks DNA synthesis
(c) destroys chromatin
(d) inhibits cell wall formation
Answer: (d) inhibits cell wall formation
Two marks questions with answers
1. What is the key difference between primary and secondary sewage treatment?
Answer: The key difference between primary and secondary treatment of sewage is that primary treatment is a physical process which removes grit and large pieces of organic matter while secondary treatment is a biological process that causes digestion of organic matter by microbes.
2. Differentiate between by biofertilizers and chemical fertilizers.
Answer: Biofertilizers are microorganisms where as chemical fertilizers are chemical formulations. Biofertilizers are very cheap while chemical fertilizers are costly Biofertilizers are slow in providing nutrients while chemical fertilizers are quick in supplying nutrients. Biofertilizers do not cause pollution where as chemical fertilizers cause pollution of environment including groundwater and surface water bodies.
3. What are flocks? State their role in effluent treatment and their ultimate fate in sewage treatment tank.
Answer: Flocs are larger heavier masses of semidecayed organic matter and microbes surrounded by slime which settle down in secondary settling tank as secondary or activated sludge. It can be used as inoculum as well as taken to anaerobic digester for regeneration of biogas. The spent sludge is then used as manure, in landfill or burnt to obtain more energy.
4. What is the role of rhizobium as bio fertilizer?
Answer: Rhizobium forms symbiotic association with the legume roots. It lives as bacteroides in the cortical cells of root nodules. Pigment leg haemoglobin occurs outside each group of bacteroids. Bacteroids pick up dinitrogen and convert the same into ammonia. The latter combines immediately with organic acids to produce amino acids. A good amount of amino acids are passed into legumes. The legumes is enriched. Therefor legumes do not require nitrogen fertilizers.
5. What is the role of microbes in the Single cell protein?
Answer: Single cell protein is protein rich microbial biomass which can be used as food and feed. Single cell protein has all the essential amino acids. Fat content is low. Both autotrophs and heterotrophs are used as SCP. Amongst autotrophs Spirulina has become an important food supplement which is used in various forms including tablets. It has 60% protein, all minerals, vitamins and unsaturated fats. Amongst heterotrophs yeast and mushrooms are being raised as SCP. There is an increasing use of low cost organic matter (saw dust, paddy, husk and other organic wastes) for raising SCP like Fusarium and common mushrooms.
Three marks questions with answers
1. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.
Answer: Chemical fertilizers are used to increase availability of minerals while chemical pesticides are employed to kill pests. They are formed from costly raw materials. As a result the prices of chemical fertilizers and pesticides are rising and reaching beyond the purchasing power of small farmers. Further the chemical fertilizers and pesticides are ecologically harmful as well as toxic to human beings and cattle.
Microbes can be used both as fertilizers and pesticides. They are respectively called biofertilizers and biopesticides. Being biological in origin they are neither harmful to ecology nor to human beings. Of course they are slow acting. Organic farming exclusively uses biofertilizers and pesticides. Even otherwise biofertilizers and biopesticides can definitely reduce the use of chemical fertilizers and chemical pesticides.
2. What is the role of microbes in soil?
Answer: Numerous microbes reside in soil they take part in the following processes
(a) Humification: Organic remains of terrestrial plants and animals fall over the soil surface. Microbes partially degrade the organic matter and convert the same into humus. Humification is essential for maintaining the soil structure, its hydration and aeration.
(b) Mineralization: During microbial degradation of organic matter, minerals are released in the soil for absorption by plants.
(c) Biofertilizers: They enhance the availability of nitrogen, phosphorus (phosphate dissolution).
(d) Denitrification: Some microbes act on nitrates and convert them into free nitrogen that escapes into the atmosphere for replenishment.
3. How do biofertilizers enrich the fertility of soil?
Answer: Biofertilizers are microorganisms which increase fertility of the soil and enhance the availability of inorganic nutrients to crop plants. They are of three main types.
(a) Nitrogen fixing bacteria and cyanobacteria: They are free living & symbiotic microbes which pick up free nitrogen from soil atmosphere and convert the same into salts of nitrogen. A part of fixed nitrogen becomes available to others immediately while the remaining becomes available after their death.
(b) Phosphate bacteria: They secrete phosphatase to dissolve the insoluble soil phosphates for absorption by plants.
(c) Mycorrhiza: Mycorrhiza occurs in most of the forest plants. It takes part in solubilization and absorption of nutrients from organic matter.
4. Microbes play a dual role when used for sewage treatment as they not only help to retrieve usable water but also generate fuel. Explain.
Answer: Microbes are used in secondary treatment of sewage in oxidation tanks, trickling filter method or activated sludge method. They consist of bacteria, cyanobacteria, fungi and green algae. The whole complex is called sewage fungus. Aerobic environment is required. Organic matter is partially digested. It forms flocks with the help of slime. Flocs settle down as sediment. It is called activated sludge. The supernatant is allowed to pass into the water bodies.
Activated sludge is taken to anaerobic digesters for generation of biogas. The spent sludge can be used as manure, in landfill or burnt to produce energy.
5. What is cryprotein?
Answer: Cryprotein is potentially toxic chemical that is produced in protoxin crystalline endotoxin state by bacterium Bacillus thuringiensis. It can be extracted from the bacterium. The protein is also present in the spores of the bacterium. The commercial product is called sporein, dipel, biostol and thuricide. It is sprayed over the crop. As the protein reaches the midgut of the insect, it is converted into toxic state by alkaline pH and digestive enzymes. The toxin binds to specific receptors present on epithelial cells, creates pores and ruptures the cells causing death of the insect
There are several types of cryproteins specific to different types of insects. The gene for cry protein called cry has been incorporated in some crop plants to provide resistance to insect pests. Such genetically modified crops plants are called Bt (after Bacillus thuringiensis) crops example Bt cotton.