Microbiology and Nitrogen Cycle

Nitrite to nitrate is converted by Nitrobacter bacteria.

Correct Answer: Pseudomonas

Dialister pneumosintes is the smallest non-fermentative, anaerobic, gram-negative rod-shaped bacteria.

In the early 1940s, American geneticists Edward Tatum and George Beadle evaluated Garrod's hypothesis using Neurospora. The one gene-one enzyme hypothesis is the idea that each gene encodes a single enzyme.

Nif genes are gene encoding enzymes that are involved in the fixation of atmospheric nitrogen into a form of nitrogen that is available to living organisms. Transcription of nitrogen fixation genes in these bacteria is induced primarily by low-oxygen conditions. Rhizobium is a symbiotic bacteria that is found in the root nodules of leguminous plants.

The conversion of ammonia to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification, the oxidation of ammonium is performed by bacteria (such as the Nitrosomonas species) which converts ammonia to nitrites. Other bacterial species (such as Nitrobacter) are responsible for the oxidation of the nitrites into nitrates.

Blue green algae help in nitrogen fixation. Rhizobium is a symbiotic bacterium that is found in the root nodules of leguminous plants. It helps in the nitrogen fixation process.

Organotroph is an organism that obtains hydrogen or electrons from organic substrates. It is usually a decomposer.

Nitrobacter is a chemosynthetic bacterium. It plays a major role in nitrogen cycle by converting nitrites into nitrates.

The correct option is (1).

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 The pea plant harbours Rhizobium bacteria that can fix nitrogen from air.

Effective nodules are formed by effective strains of rhizobium. They are well-developed and pink-coloured due to the presence of a pigment called leghaemoglobin. 

Nitrogenase is the enzyme used by some organisms to fix atmospheric nitrogen gas (N₂). It is the only known family of enzymes, which accomplishes this process.