Microbes in Human Welfare Online Test 12th Science Questions in English

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• Microbes such as bacteria, fungi, protozoa, certain algae, viruses, viroids and prions are some of the major components of the biological system on Earth.

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Microbes are present everywhere – in soil, water, air and within bodies of animals and plants. Microbes like bacteria and fungi can be grown on nutritive media to form colonies which can be visibly seen.

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Bacteria like Lactobacillus acidophilus, L. lactis and Streptococcus lactis commonly called lactic acid bacteria (LAB) are probiotics which check the growth of pathogenic microbes in the stomach and other parts of the digestive tract.

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In everyday life, microbes and their products are used in the preparation of idli, dosa, cheese, curd, yogurt, dough, bread, vinegar, etc.,

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The LAB (lactic acid bacteria) grows in milk and convert it into curd, thereby digesting the milk protein casein.

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A small amount of curd added to fresh milk as a starter or inoculum contains millions of Lactobacilli, which under suitable temperature (≤40oC) multiply and convert milk into curd.

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Curd is more nutritious than milk, because curd contains a large number of organic acids and vitamins.

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Prebiotics are compounds in food (fibres) that induce the growth or activity of beneficial microorganisms.

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Probiotics are live microorganisms intended to provide health benefits when consumed, generally by improving or restoring the gut flora.

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Yogurt is produced by the bacterial fermentation of milk, and lactic acid is produced as a by-product. 

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Microorganisms such as Streptococcus thermophilus and Lactobacillus bulgaricus coagulate the milk protein and convert the lactose in the milk to lactic acid. The flavour in yogurt is due to acetaldehyde.

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• Cheese is a dairy product produced in a wide range of flavours, textures and is formed by coagulation of the milk protein, casein. During cheese production, milk is usually acidified and the enzyme rennet is added to cause coagulation. The solids are separated and pressed to form cheese. Most cheese are made with a starter – bacteria, Lactococcus, Lactobacillus or Streptococcus.

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Paneer (cottage cheese) is fresh cheese common in South Asia, especially in India. It is made by curdling milk with lemon juice, vinegar and other edible acids.

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Large holes in Swiss cheese is due to the production of large amount of carbon-di-oxide by the bacterium Propionibacterium shermanii.

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The dough used in the preparation of idlis and dosas are fermented by the bacteria Leuconostoc mesenteroides.

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The dough which is used in bread making is fermented by Saccharomyces cerevisiae (Baker’s Yeast).

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Fermentation of glucose mainly forms ethyl alcohol and carbon di-oxide, which is responsible for leavening of dough. When leavened dough is baked, both carbon-di-oxide and ethyl alcohol evaporate making the bread porous and soft.

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• Single cell protein refers to edible unicellular microorganisms like Spirulina. Protein extracts from pure or mixed cultures of algae, yeasts, fungi or bacteria may be used as ingredient or as a substitute for protein rich foods and is suitable for human consumption or as animal feed.

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• Microbes are used to synthesize a number of products valuable to human beings. Products like beverages, antibiotics, organic acids, amino acids, vitamins, biofuels, single cell protein, enzymes, steroids, vaccines, pharmaceutical drugs, etc., are produced in industries.

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• Production on a large scale requires growing microbes in very large vessels called fermentors. A fermentor (bioreactor) is a closed vessel with adequate arrangement for aeration, agitation, temperature, pH control and drain or overflow vent to remove the waste biomass of cultured microorganisms along-with their products.

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Antibiotics are chemical substances produced by microorganisms which can kill or retard the growth of other disease-causing microbes even in low concentration. Antibiotic means “against life”.

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Antibiotics are used to treat diseases such as plague, meningitis, diphtheria, syphilis, leprosy, tuberculosis etc., Selman Waksman discovered Streptomycin and was the first to use the term “antibiotic” in 1943.

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While working on Staphylococci bacteria, Alexander Fleming observed a green mould growing in one of his unwashed culture plates around which Staphylococci could not grow.

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Alexander Fleming found that it was due to a chemical produced by the mould and he named it as penicillin, which was the first antibiotic discovered by Alexander Fleming in 1926.

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Penicillin is produced by the fungi Penicillium notatum and Penicillium chrysogenum. It is bactericidal (antibiotics that kill bacteria) in action and inhibits the synthesis of the bacterial cell wall.

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Penicillin is also referred as the “queen of drugs” and its full potential as an effective antibiotic was established much later by Earnest Chain and Howard Florey when they treated the wounded soldiers in World War II with penicillin.

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Alexander Fleming, Chain and Florey were awarded the Nobel prize in 1945 for the discovery of penicillin.

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Antibiosis is the property of antibiotics to kill microorganisms. Broad-spectrum antibiotics act against a wide range of disease-causing bacteria. Narrow-spectrum antibiotics are active against a selected group of bacterial types.

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Hypersensitivity reaction of Penicillin is a major problem with the use of penicillin, resulting in nausea, vomiting, wheezing and ultimately cardiovascular collapse.

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• To check the sensitivity reaction, doctors use a needle to prick the forearm of the patients to give a weak dose of penicillin. An itchy red region in the forearm is an indication that the patient is allergic to penicillin. This test is important before administration of penicillin to a patient.

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Tetracycline is a broad- spectrum bacteriostatic antibiotic (antibiotics that limit the growth of bacteria) that inhibits microbial protein synthesis.

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Chlortetracycline is the first antibiotic of this group, isolated from the cultures of Streptomyces aureofaciens.

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Streptomycin is a broad- spectrum antibiotic isolated from the actinomycetes, Streptomyces griseus. It is bactericidal against both gram positive and gram- negative bacteria, especially against Mycobacterium tuberculosis.

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Antibiotics, such as erythromycin, chloromycetin, griseofulvin, neomycin, kenamycin, bacitracin, etc., are also isolated as microbial products.

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Antibiotic resistance occurs when bacteria develop the ability to defeat the drug designed to kill or inhibit their growth. It is one of the most acute threat to public health. Antibiotic resistance is accelerated by the misuse and over use of antibiotics, as well as poor infection prevention control. Antibiotics should be used only when prescribed by a certified health professional.

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“Superbug” is a term used to describe strains of bacteria that are resistant to the majority of antibiotics commonly used today.

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Microbes especially yeast is being used from time immemorial for the production of beverages like wine, beer, whisky, brandy and rum.

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Wine is among the oldest alcoholic beverages known and is produced by fermentation of fruit juice by yeast.

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Zymology is an applied science which deals with the biochemical process of fermentation and its practical uses.

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Saccharomyces cerevisiae commonly called brewer’s yeast is used for fermenting malted cereals and fruit juices to produce various alcoholic beverages.

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Wine and beer are produced without distillation, whereas whisky, brandy and rum are obtained by fermentation and distillation.

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The Pasteur effect is the inhibiting effect of oxygen on the fermentation process.

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Oenology is the science and study of wine and wine making. Wine is made from the fermentation of grape juice.

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Grape juice is fermented by various strains of Saccharomyces cerevisiae into alcohol. Grape wine is of two types, red wine and white wine.

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For red wine, black grapes are used including skins and sometimes the stems also are used. In contrast white wine is produced only from the juice of either white or red grapes without their skin and stems.

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Beer is produced from germinated barley malt grain by Saccharomyces carlsbergensis or Saccharomyces cerevisiae. Rum is made from fermented sugarcane or molasses or directly from sugarcane juice by Saccharomyces cerevisiae. Whisky is a type of distilled alcoholic beverage made from fermented grain mash by Saccharomyces cerevisiae.

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Wine contains 9 to 14 percent alcohol. Wine coolers are made of wine mixed with carbonated water and flavourings. Wine coolers have about 4 to 6 percent alcohol.

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Beer contains 3 to 5 percent of alcohol. Distilled spirits such as whiskey, gin, scotch and vodka usually contain 35 to 50 percent alcohol.

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In some parts of South India, a traditional drink called pathaneer is obtained from fermenting sap of palms and coconut trees.

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A common source is tapping of unopened spadices of coconut. It is a refreshing drink, which on boiling produces jaggery or palm sugar.

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When pathaneer is left undisturbed for few hours it gets fermented to form toddy with the help of naturally occurring yeast, to form a beverage that contains 4 percent alcohol. After 24 hours toddy becomes unpalatable and is used for the production of vinegar

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Saccharomyces cerevisiae is the major producer of ethanol (C2H5OH). It is used for industrial, laboratory and fuel purposes. So, ethanol is referred to as industrial alcohol. Bacteria such as Zymomonas mobilis and Sarcina ventriculi are also involved in ethanol production.

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The two most common type of biofuels in use today are ethanol and biodiesel, both of them represent the first generation of biofuel technology.

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The process of ethanol production starts by milling a feed stock followed by the addition of dilute or fungal amylase (enzyme) from Aspergillus to break down the starch into fermentable sugars. Yeast is then added to convert the sugars to ethanol which is then distilled off to obtain ethanol which is up to 96 percent in concentration. Ethanol is often used as a fuel, mainly as a biofuel additive for gasoline.

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Biodiesel is a fuel made from vegetable oils, fats or greases. Biodiesel fuel can be used in diesel engines without altering the engine

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The Government of India approved the National Policy on Biofuels in December 2009. Pure biodiesel is non-toxic, biodegradable and produces lower level of air pollutants than petroleum-based diesel fuel.

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The Government of India identified Jatropha curcas as the most suitable oilseed for biodiesel production. Pongamia species is also a suitable choice for production of biodiesel.

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World biofuel day is observed every year on 10th August to create awareness about the importance of renewable bio-fuels as an alternative to conventional non-renewable fossil fuels. This day also highlights the various efforts taken by the Government in the biofuel sector.

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Examples of organic acid producers are Aspergillus niger for citric acid, Acetobacter aceti for acetic acid, Rhizopus oryzae for fumaric acid, Clostridium butyricum for butyric acid and Lactobacillus for lactic acid.

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Yeast (Saccharomyces cerevisiae) and bacteria are used for commercial production of enzymes. Lipases are used in detergent formulations and are used for removing oily stains from the laundry.

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Bottled juices are clarified by the use of pectinase, protease and cellulase. Lipases are used in detergent formulations and are used for removing oily stains from the laundry.

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Rennet can also be used to separate milk into solid curds for cheese making. Streptokinase produced by the bacterium Streptococcus and genetically engineered Streptococci are used as “clot buster” for removing clots from the blood vessels of patients who have undergone myocardial infarction.

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Cyclosporin A, an immunosuppressant used in organ transplantation is produced from the fungus Trichoderma polysporum.

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Cyclosporin A is also used for important properties such as anti-inflammatory, antifungal and anti-parasitic.

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Statins produced by the yeast Monascus purpureus have been used to lower blood cholesterol levels.  Recombinant human insulin has been produced predominantly using E. coli and Saccharomyces cerevisiae for therapeutic use in human.

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Sewage is the waste generated every day in cities and towns containing human excreta. It contains large amounts of organic matter and microbes, which are pathogenic to humans and are bio-degradable pollutants. Domestic waste consists of approximately 99 percent water, suspended solids and other soluble organic and inorganic substances. Sewage should not be discharged directly into natural water bodies like rivers and streams. Before disposal, sewage should be treated in sewage treatment plants to make it less polluting.

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Microbes (mass of bacteria floc) are allowed to grow in aerated water (secondary treatment). They consume major part of organic matter in the effluent and reduce the BOD in the waste water

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A microbial fuel cell is a bio-electrochemical system that drives an electric current by using bacteria and mimicking bacterial interaction found in nature. Microbial fuel cells work by allowing bacteria to oxidize and reduce organic molecules. Bacterial respiration is basically one big redox reaction in which electrons are being moved around. A MFC consists of an anode and a cathode separated by a proton exchange membrane. Microbes at the anode oxidize the organic fuel generating protons which pass through the membrane to the cathode and the electrons pass through the anode to the external circuit to generate current.

Explanation 

Biogas is a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural wastes, manure, municipal wastes, plant material, sewage, food waste, etc., Biogas is produced under anaerobic condition, when the organic materials are converted through microbiological reactions into gas and organic fertilizer.

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Biogas primarily consists of methane (63 percent), along with CO2 and hydrogen. Methane producing bacteria are called methanogens and one such common bacterium is Methano-bacterium.

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The Methanogens are also present in anaerobic sludge and rumen of cattle. In rumen, these bacteria help in the breakdown of cellulose. The excreta of cattle called dung is commonly called “Gobar”. Gobar gas is generated by the anaerobic decomposition of cattle dung. It consists of methane, CO2 with some hydrogen, nitrogen and other gases in trace amounts.

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Biogas 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).

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Aerobic microbes degrade the pollutants in the presence of oxygen. They mainly degrade pesticides and hydrocarbons. Pseudomonas putida is a genetically engineered microorganism (GEM). Ananda Mohan Chakrabarty obtained patent for this recombinant bacterial strain. It is multi- plasmid hydrocarbon-degrading bacterium which can digest the hydrocarbons in the oil spills.

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Ideonella sakaiensis is currently tried for recycling of PET plastics. These bacteria use PETase and MHETase enzymes to breakdown PET plastic into terephthalic acid and ethylene glycol

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Nitrosomonas europaea is also capable of degrading benzene and a variety of halogenated organic compounds including trichloroethylene and vinyl chloride.

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Anaerobic microbes degrade the pollutants in the absence of oxygen. Dechloromonas aromatica has the ability to degrade benzene anaerobically and to oxidize toluene and xylene.

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Phanerochaete chrysosporium an anaerobic fungus exhibits strong potential for bioremediation of pesticides, polyaromatic hydrocarbons dyes, trinitrotoluene, cyanides, carbon tetrachloride, etc., Dehalococcoides species are responsible for anaerobic bioremediation of toxic trichloroethene to non-toxic ethane.