Test: Microbes in Human Welfare - NEET MCQ

Curd is more nutritious than milk as it contains a number of organic acids and vitamins including B12. LAB present in curd also checks growth of disease causing microbes in stomach and other parts of digestive tract. 

 Microbes have been used for long time in production of dairy products like curd, yoghurt, cheese, etc. Yoghurt is produced by curdling milk with the help of Streptococcus thermophilus and Lactobacillus bulgaricus. Yoghurt has higher nutritional value than milk thus, it can be said that Streptococcus thermophilus increases nutritional value of milk. 

Besides cereals, green vegetables, brewer's yeast, egg white, vitamin B2 is also produced by intestinal bacteria. The vitamin was first obtained in 1938 using wild strain of mould Ashbhya gossypii. Vitamin B2  is essential for normal growth and reproduction in a number of laboratory animals. 

 Litmus is an important and widely used dye in chemical laboratories as an acid-base indicator. It is obtained from Rocella montaignei. Orcein, a biological stain, is obtained from Rocella tinctoria. 

Yeast is a fermentation agent. It is a known fact that yeast raises bread dough to rise and hence, Yeast is also used to increase the volume, making the dough porous and the product soft. It is the yeast that helps the dough to rise. 

 Rennet is obtained from calf 's stomach and is a commercially available form of enzyme rennin. Rennet is used from curdling of milk to initiate the process of cheese formation. The same function can be carried out with the help of fruit extract of Withania somnifera. Thus, rennet and fruit extract of Withania somnifera have similar functions and are not antagonistic.

 Toddy is a traditional drink of some parts of South India which is made by fermentation of sap of palms. Toddy left for few hours undergoes fermentation with the help of naturally occurring yeast to form beverage containing about 6% alcohol. But after about 24 hours, toddy becomes unpalatable because fermentation is carried on. At this time, it can be used for production of vinegar. 

 Beer, wine, gin, rum, vodka, etc. are fermentation products but beer and wine are formed without distillation. However, distillation of fermented broth is carried out in case rum, gin, etc. Distillation increases the alcohol concentration of the beverage. Thus, gin with 40% alcohol, rum with 40% alcohol and brandy with 60-70% alcohol are more alcoholic than beer (3-6% alcohol) and wine (9-12% alcohol). 

Antibiotics are chemical substances produced by some microbes which in small concentration can kill or retard the growth of harmful microbes without adversely affecting the host. Griseofulvin is an antibiotic produced by Penicillum griseofulvum and is antifungal in nature, especially effective against ringworm. Ringworm is caused by dermatophytic fungi like Epidermophyton, Trichophyton, Microsporium, etc. which cannot grow in presence of P. griseofulvum because of the antagonistic effect of antibiotic griseofulvin secreted by it. 

Acetic acid is prepared from fermented alcohols with the help of acetic acid producing bacteria, Acetobacter aceti. Alcoholic fermentation of sugars is an anaerobic process but the conversion of alcohol to acetic acid is an aerobic process. This reactions occurring can be summarised as: Anaerobic formation of alcohol:

Acetic acid is either used as vinegar after ripening or in pharmaceuticals, colouring agents, insecticides, plastics, etc.  

 Cyclosporin is cyclic oligopeptide obtained-through fermentative activity of fungus Trichoderma polysporum. It has immunosuppressive properties and inhibits activation of T-cells. T cells of immune system mainly function to kill non-self cells. Because cyclosporin A inhibits T cells function, it causes immunosuppression and chances of rejection of transplanted organ are reduced. Thus, organ transplant patients are provided with cyclosporin A. 

A small quantity of yeast is added to wheat flour and is kneaded. The kneaded flour is kept at a warm temperature for few hours. It swell up. This phenomenon is called leavening. Leavening is caused by secretion of three types of enzymes by yeast. These are amylase, maltase and zymase.

Sacharomyces cerevisiae produces an enzyme called zymase which can cause fermentation to produce alcohol. 

 Sewage treatment is divided into primary treatment and secondary treatment. Primary treatment involves filtration of the sewage and then sedimentation of the debris present on filtrate. No microbes are used. The sediment of primary treatment, called primary sludge, is treated by aerobic microbes and then by anaerobic microbes to reduce its organic components during secondary treatment. Secondary treatment involves microbes, thus it is also called biological treatment. 

 Biogas is an excellent example of beneficial functions of microbes. It is a mixture of CH4, CO2, H2S, etc. and is produced by the action of methanogenic bacteria on fecal organic matter. It has wider applications than the direct burning of organic wastes (as dungcakes) and it is an easily storable form of energy which can be used more efficiently and economically. The energy value of biogas is lower than that of organic matter but due to more efficient handling, the net energy output is roughly equal to direct burning of organic wastes. Besides biogas production minimises the chances of spread of fecal pathogens and produces manure which has fertilizer value similar to that of manure formed directly from organic wastes. 

 Gases present in bio-gas produce energy by combustion or oxidation which can be used for heating purpose or for generation of power through gas engines. Biogas is used as fuel for heating and cooking, lighting, power for irrigation and other purposes as an alternative of firewood, kerosene, dung cakes or even electricity and pollution free source of energy.

 Bioenergy is the energy extracted from biological sources, both living and their immediate remains e.g. wood, gobar gas. It does not include fossil fuels (coal, petroleum, natural gas etc.)

 Some fungi form a mutually beneficial or symbiotic association with the roots of higher plants. In seedling stage of most orchids, the fungal hyphae not only increase absorption frequency but also provide nourishment by forming nutrient rich cells.

 Microbes are extensively used in human welfare but they sometimes prove harmful too. Most of the human, animal and plant diseases occur because of infections caused by micro-organisms. Viruses are nucleoprotein complexes that cause disease. But nucleic acid alone and proteins alone can also cause diseases. Disease causing nucleic acid complexes are termed viroids while prions are proteinaceous infectious agents.

Baculoviruses and dragonflies act as biocontrol agents. Biocontrol agents are organisms that control population of some harmful organisms. Dragonflies prey upon mosquito larvae and thus, check mosquito population. Hence, they serve to control spread of mosquito borne diseases like malaria, dengue, etc. Baculoviruses are effective narrow spectrum bioinsecticides which are specific for their target insects and do not have side effects on plants, mammals, birds, fish and non-target insects. Thus, these are widely used in fields.