Question

One of the free-living anaerobic nitrogen-fixer is?

• A. Rhizobium
• B. Azotobacter
• C. Rhodospirillum
• D. Beijernickia

Answer 1

The correct option is C

Rhodospirillum

The correct option is C:

Explanation for Correct option:

1. Rhodospirillum is a free-living nitrogen-fixing bacteria.
2. Because it is a facultative anaerobe, it can use alcoholic fermentation in low-oxygen environments or aerobic respiration in high-oxygen environments.

Explanation for Incorrect options:

Option A:

1. Rhizobium is a nitrogen-fixing symbiotic bacteria found in the root nodules of legume plants.

Option B:

1. Azotobacter species were emphasized as essential free-living N2-fixing bacteria.
2. It is aerobic as it can strictly live only in the presence of oxygen.

Option D:

1. Azotobacter and Beijerinckia are nitrogen-fixing microbes that live in an aerobic environment.

Final answer: One of the free-living anaerobic nitrogen-fixer is Rhodospirillum.