Question

A bacterium which is capable of utilizing the most abundantly available gas in the atmosphere for one of its metabolic pathways, but cannot utilize the second most abundantly available for its another metabolic pathway is

Answer 1

Rhizobium is a bacteria which fixes N2, which is the most abundant gas ,as NH3. But Rhizobium can only do this in the absence of O2, second most abundant gas, as the enzyme it uses , leghaemoglobin requires anaerobic conditions.
Thus it can function in presence of N2 and not in presence of O2.

Answer 2

The plants are capable of utilizing other forms of nitrogen with ease and facility. Let us have look at major metabolic pathways in a figure that shows most but not all.

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