Question

The process of nitrogen-fixation by bacteria does not take place in the presence of

• A. Molecular form of hydrogen
• B. Elemental form of oxygen
• C. Water
• D. Elemental form of nitrogen

Answer 1

The correct option is B Elemental form of oxygen

Nitrogen-fixation is a process in which the atmospheric nitrogen ($N_2$) is converted to ammonium ($N{H}_4^{+}$), nitrates($N{O}_3^{-}$) or nitrites ($N{O}_2^{-}$). Nitrogen fixation can be natural or synthetic. Under natural mode of nitrogen fixation, some bacteria called nitrogen fixing bacteria carry out this process. Atmospheric nitrogen or $N_2$ is relatively inert but nitrogen fixing bacteria possess enzyme nitrogenase which is involved in nitrogen fixation. But nitrogenase enzyme is susceptible to destruction by elemental form of oxygen. Due to this, nitrogen-fixing bacteria live in anaerobic environment as in root nodules. Therefore, option B is correct.