Microbes in Human Welfare Test - 25

Pyrethrum is a genus of plants which are cultivated as ornamentals. It is a natural insecticide made from the dried flower heads of Chrysanthemum cinerariifolium. Pyrethroids are synthetic insecticides derived from natural Pyrethrum (pyrethrins). The compound enhances the effect of toxicity to insects. These compounds target the nervous system of the insects. They are commonly used as insect repellants. 

Waksman and his students isolated more than fifteen antibiotics. Waksman identified the first true antibiotic. He observed an antibiotic in Actinomyces antibioticus, a member of the actinomycetes family. The microbe produced a substance, actinomycin. Actinomycin had both bacteriostatic and bactericidal properties. 

Domestic sewage consists biodegradable organic matter and easily decomposes by the micro-organisms. These microorganisms can multiply using these organic substances as substrates and hence, utilize some of the components of sewage. Micro-organisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, and as a result, there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. This causes mortality of fish and other aquatic creatures. 

Antibiotics are chemical substances produced by the microorganisms that can kill or inhibit the growth of other bacteria and fungi. Alexander Fleming discovered penicillin, the first antibiotic in 1928, made from the Penicillium notatum.

• Antibiotics are chemical substances produced by microorganisms that can kill or inhibit the growth of other bacteria and fungi, thus used to treat bacterial and fungal infections. 
• Many antibiotics like penicillin target bacterial cell wall synthesis, while others inhibit protein synthesis by targeting prokaryotic ribosomes. The ribosome serves the cell as a protein-making machine.
  
• Viruses don't have cell walls or their own cellular machinery that can be attacked by antibiotics.

A biofertilizer is a fertilizer containing living microorganisms. When applied to plant surfaces or soil, they colonize the rhizosphere or the interior of the plant and promotes growth by increasing the availability of nutrients to the host plant. 

Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. It is bacteriostatic.
Erythromycin belongs to a group of drugs called as macrolide antibiotics. Macrolide antibiotics slow the growth of, or sometimes kill, sensitive bacteria by reducing the production of important proteins needed by the bacteria to survive.

Correct option A

Explanation for correct option:

• Earthworms are commonly found living in the soil. They feed on dead organic matter. They help in the conversion of large pieces of organic matter into rich humus. This property helps to increase soil fertility. 
• Oscillatoria is the genus of blue-green algae. They are found in freshwater. Oscillatoria helps in nitrogen fixation and improves the quality and fertility of the soil. They are commonly used as a biofertilizer in paddy fields. 

• Glomus is the species that form the mycorrhizal association with the roots of the legumes and oilseed plants. These fungi help in the mineral uptake by the plants. 
  
  
• Snail is not used in organic farming.

Correct Option: C

Explanation:

• Frankia is nitrogen-fixing bacteria.

• it shows a symbiotic relationship with plants and lives in soil. 

• species of this genus Frankia belongs to gram-positive bacteria.

• Rhizobium is nitrogen-fixing bacteria. they belong to gram-negative soil bacteria. 

• it forms root nodules in the plant cells, and they convert the atmospheric nitrogen into ammonia using the enzyme nitrogenase.

• Azospirillum is used in rice fields as a biofertilizer. rice fields are also known as paddy fields where this azospirillum are used as a nitrogen-fixing organism.

• it’s a symbiotic nitrogen-fixing bacteria.

Hence, The common nitrogen-fixer in paddy fields is azospirillum.