Question

Nitrogen fixation is inhibited by oxygen. However, in aerobic nitrogen-fixing bacteria, nitrogen is fixed in the presence of oxygen. Nitrogenase in such organisms is protected by which one of the following mechanisms.

• A. Channelizing oxygen to form ozone.
• B. Removal of oxygen by metabolic activity.
• C. Utilizing oxygen for membrane remodeling.
• D. Utilizing oxygen for synthesis of pentapeptide chain in peptidoglycan.

Answer 1

The correct option is B Removal of oxygen by metabolic activity.

Nitrogen fixation is a process by which nitrogen ($N_2$) is converted into ammonia ($N{H}_3$). Nitrogen fixation is carried out naturally in the soil by nitrogen-fixing bacteria such as Azotobacter. Some nitrogen-fixing bacteria have symbiotic relationships with some plant groups, especially legumes. Nitrogen fixation is carried out by the enzyme nitrogenase, which is found in microbes.

Conversion of $N_2$ to ammonia ($N{H}_3$) by bacteria is energetically expensive and extremely sensitive to $O_2$. Both proteins that makeup nitrogenase are irreversibly denatured by the presence of $O_2$. All systems that support nitrogenase have evolved mechanisms of creating a low $O_2$ environment at the site of $N_2$ fixation. The $O_2$ is removed by the organism through various metabolic pathways.

So, the answer is B.