Question

The plasmid of which one of the following has the ‘Nif’ gene in it?
(A) Rhizobium
(B) Agrobacterium tumefaciens
(C) Bacillus thuringiensis
(D) Salmonella typhimurium

Answer 1

Hint: The full form of Nif is the nitrogen fixation. Some of the microorganisms have this gene in them to store the nitrogen from the atmosphere in the roots of the plants. Which in turn, this nitrogen is used by the plants for its growth.

Complete step by step answer:
Rhizobium is the type of bacterium which is found on the roots of the plants. These are found only in the plants which are leguminous in nature. These plants have bulge-like structures in their roots and these structures are called nodules. The rhizobium fixes the atmospheric nitrogen in these plants’ nodules. This nitrogen is converted into the ammonia and is used by the plants for its growth and development.

This nitrogen fixing is the ability that comes from the ‘Nif’ gene in their nucleic acid. The plant in turn provides shelter for the rhizobium bacteria for its growth. Thus, these two organisms are in a symbiotic relationship with each other. These are known as symbionts. Hence the plasmid of the rhizobium has the ‘Nif’ gene in it.

So, the correct answer is “Option A”.

Note:
These rhizobia have enormous values in the field of agriculture. This is because they fix most of the atmospheric nitrogen in the soil. Hence this is used as the bio fertilizer which increases the yield of the agricultural crops and reduces the use of artificial fertilizer.