Biology & Human Welfare Test - 6

The term antibiotic was first used  in 1942 by Selman Waksman and his collaborators in journal articles to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution.

Microorganisms such as Lactobacillus and others commonly called Lactic Acid Bacteria (LAB) grow it milk and convert into curd. During growth, the LAB produce acids that coagulate and partially digest the milk proteins. A small amount of curd added to the fresh milk as inoculums or starter contain millions of LAB, which at suitable temperature multiply, thus, converting milk to curd, which also improves its nutritional quality by increasing vitamin-B12 Note In our stomach, the LAB play other options are not related with LAB bacteria beneficial role in checking disease causing microbes. 

Methanogens are bacteria which grow on cellulosic material and produce a  large amount of methane along with CO₂  and H_2. For example: Methanobacterium
Methanogens are the  bacteria  found in cattle dung (gobar) and in anaerobic sludge during sewage treatment. They  grow  anaerobically on cellulosic material and produce  a large amount of methane (the  main constituent of biogas) along with CO₂   and H₂ . These methanogens are grown on slurry which comprises of cattle dung where they act upon the dung and lead to its breakdown and release of gases like methane and carbon-dioxide. Thus, methanogens are used in biogas production.

Answer

• Many of the species of the domain Eubacteria are used for the production of antibiotics such as streptomycin, etc.
• Where as Actinomycetes are anaerobic bacteria which can be or cannot be pathogenic with resistance against various antibiotics.
• Fungi are used to produce antibiotics  but compared to the number of bacterial species that secret antibiotics the number of fungi secreting antibiotic is less.
• Viruses never secret antibiotic.
• So, the answer is 'Viruses '

Penicillin is a secondary metabolite of certain species of Penicillium and is produced when the growth of the fungus is inhibited by stress. It is not produced during active growth. Production is also limited by feedback in the synthesis pathway of penicillin.

So, the correct option is 'Penicillium '.

Saccharomyces cerevisiae
Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars.

The word activated sludge system is derived from the practice of adding aerobic heterotrophic bacteria to the incoming sewage, from a previous batch. This sludge inoculum contains large numbers of  metabolising  bacteria, together with yeasts, molds, and Protozoa. An especially important ingredient of the sludge are species of. Zoogloea bacteria, which form flocculant masses (floc) in the aeration tanks.

The activity of these aerobic micro-organisms  oxidises  much of the effluent 's organic matter into carbon dioxide and water. When the aeration phase is completed, the floc (secondary sludge) is allowed to settle to the bottom, just as the primary sludge settles in primary treatment.

Probiotics are live microbial food supplements that provide several health benefits, as they help in maintaining excellent stability and composition of the intestinal microbiota and boost the resistance against infection by pathogens. 

Fermentation is a metabolic process which leads to chemical changes in organic substrates through the action of the enzymes. Most organisms carry out fermentation through a chemical reaction that converts the pyruvate from glycolysis into lactic acid or lactate. Lactic acid fermentation also converts NADH into NAD⁺ so that glycolysis can continue.

Rennin, also known as chymosin, is an enzyme that can be easily found in the rennet. It is usually produced by the 4^th stomach chamber of the cows, called abomasum. Rennin is also used in the dairy industry for the making of cheese.