Tag: useful and harmful bacteria

Anabaena belongs to the family of filamentous cyanobacteria that is known for its nitrogen fixing ability. While these exists as a plankton, it is known to form symbiotic relationships with the water fern Azolla and are found growing together at the surface of streams and ponds on temperate and tropical regions.
Therefore, the correct answer is option A.

The antibiotics are substances produced by the natural metabolic processes of spore forming aerobic bacteria and fungi as their natural defense against other microorganisms. Among bacteria and fungi, bacterial genera outnumber the fungal genera in production of antibiotics. The highest numbers of antibiotics are derived from bacterial genera Streptomyces and Bacillus and fungal genera Penicillium and Cephalosporium. This makes option A correct. Viruses do not perform any metabolic activity outside the host and hence, do not produce any antimicrobial agents. Angiosperms are most developed flowering plants that have number of adaptation to make them less susceptible for competition for food and space; they do not produce antibiotics. Thus, the correct answer is option is A.

Nitrogen fixing bacteria like rhizobium lives in symbiotic relationship with legumes.

Under optimum condition and temperature, most of the bacteria divides at interval of 20 minutes and this time is called their generation time. This is the time in which one bacterial cell divides and forms two cells. This is also known as the doubling time. 

The plasmid is an extrachromosomal material in bacteria and used as a carrier DNA because it has antibiotic resistance gene which makes it easy to isolate the transformed cell with the desired insert in it.

Azotobacter has a wide variety of metabolic abilities, including the unusual ability to fix atmospheric nitrogen as they produce nitrogenase enzyme and convert it to ammonia. They are free living in soil and do not associate as symbionts. 

Fermentation is a process of anaerobic respiration that converts sugar to acids, gasses or alcohol. It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. The food processing industry depends on this phenomenon for deriving a variety of edible products and beverages. As viruses are the acellular organism, they do not follow respiration. Protista are the eukaryotic unicellular and respire like animals. Thus, the correct answer is option D.

Some bacteria can fix atmospheric nitrogen, e.g., Azotobacter and Clostridium, while others convert ammonia into nitrate, e.g., Nitrosomonas.
A biogeochemical cycle or substance turnover or cycling of substances is a pathway by which chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water etc move through both biotic and abiotic compartments of earth. All of these are required to carry out basic life processes as these processes supply with energy and nutrients. Thus, the correct answer is option D.

Cyanobacteria, which have "symbiotic" relationships with cycads are in the order Nostocales. Anabaena cycadeae is a blue green algae (BGA) commonly found in the coralloid roots of cycads. At first, the cycad sprouts without any cyanobacterium. Coralloid roots are formed soon after the primary root.
So answer is - 'Cycas'.

Heterotrophic bacteria require an organic carbon source for growth (i.e., they derive energy and carbon from organic compounds). Economically important uses of heterotrophic bacteria are:

1. They enhance the fertility of the soil by nitrogen fixation.
2. Production of curd and yogurt from milk, cheese, butter, wine
3. Production of antibiotics
4. They form an essential part of biogeochemical cycles during which they release essential elements, such as nitrogen and carbon for recycling.
5. Cleaning of oil spills

So answer is - 'Heterotrophic bacteria'.