A broad spectrum antibiotic is the one which is effective against both Gram(+) and Gram(-) bacteria. e.g., chloramphenicol.

Yes, microbes can be used as a source of energy, e.g. methanogens like Methanobacterium are used to produce biogas, which is a source of energy.

1. Some molecules produced by a certain living organisms perform functions in the body of other organisms and modify their metabolism.

2. Hence they are called bioactive molecules. Statins and cyclosporin A are bioactive molecules.

1. Monascus purpureus is the source of stain
2. Statins are used as blood cholestrol lowering agents, as they competitively inhibit the enzyme responsible for the synthesis of cholesterol

Primary sewage treatment is a physical process and secondary treatment is a biological process.

1. Streptococcus: It produces streptokinase enzyme that is used to dissolve clots formed in the blood vessels.
2. Monascus (Yeast) : It produces statins that help in lowering blood cholesterol levels.
3. Trichoderma (Fungus) : It produces cyclosporin A that is used as an immunosuppressant agent in organ transplantation. It inhibits activation of T-cells and thus prevents rejection of transplants.

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. The microbes biodegrade the major part of the organic matter in the effluent by using the dissolved oxygen. It reduces the BOD of the effluent.
When the BOD of sewage is reduced significantly, the effluent is passed into a settling tank where the bacterial flocs are allowed to sediment forming the activated sludge. Hence, higher the value of BOD, more is the water polluted and more is the amount of biodegradable matter in it.

The name of gobar gas (or biogas) is methane.It is generated by the activity of methanogenic bacteria (i.e., methane producing anaerobic bacteria). Following are advantages of using methane as a source of energy:
(i) Methane is insoluble and therefore, separates very easily from the fermentor.
(ii) It can be very easily pressurized or liquefied for storage
(iii) It is readily combustible.

(a) Single Cell Protein (SCP) are basically produced from the microbes, for example Candida utilis, Chlorella, Spirulina, Saccharomyces. SCP may be used directly as human food supplement or else it can be used in animal feed as protein-rich supplement.
(b) Soil It is a unique habitat which harbours a variety of microflora and fauna, and gives mechanical and nutritional support to higher plants on which human civilization is based.
Examples The rhizosphere micro-organisms have beneficial effects on the development of plant. The microorganisms catalyze the reactions in the rhizosphere and produce \({ CO }_{ 2 }\) and form organic acids that in turn solubilize the inorganic nutrients of plants. Some of the rhizosphere micro-organisms also produce growth stimulating substances.

(a) (i) These viruses are species - specific and narrow spectrum insecticides that attack insects and other Arthropods.
(ii) They have no negative impacts on non-target insects, plants, and other animals.
(b) Organic farming refers to the use of biofertilisers and biopesticides. Organic farming is advised for the following reasons:
(i) The chemical fertilisers cause pollution of environment and in the long run make the soil unsuitable for cultivation.
(ii) The manufacture of chemical fertilisers depends on the natural resources and cause their depletion.

(i) It would be helpful to humans as microorganisms are fast growing, the food is rich in nutrients and it reduces pollution.
(ii) Initially, there can be very low response, but it is expected to have high response (as of mushroom culture in the recent years).
(iii) Recycling nutrients and minimising pollution for the betterment of the environment.

(i) These are the substances used during transplant which suppress the immune system of the recipient so that the transplanted organ is not rejected due to incompatibility between donor and recipient.
(ii) Cyclosporin A; Trichoderma (fungus)
(iii) Doctor educated the patient's wife and removed her doubts.