Question

Which of the following is free-living nitrogen-fixing bacteria present in the soil?

• A. Azotobacter
• B. Nitrosomonas
• C. Rhizobium
• D. Pseudomonas

Answer 1

The correct option is A

Azotobacter

The correct answer is option A

Explanation for the correct answer:

1. Nitrogen fixation: It is the process by which inorganic atmospheric nitrogen is converted into the soluble, organic form.
2. Certain nitrogen-fixing bacteria contain the enzyme Nitrogenase that is responsible for this fixation reaction.
3. Azotobacter sp is a free-living bacteria found in the soil that fixes the atmospheric nitrogen into nitrates and nitrites.

Explanation for incorrect answer:

Option B:

Nitrosomonas: It is the nitrifying bacteria found in close association with the plant which oxidizes ammonia into nitrite

Option C:

Rhizobium: It is a symbiotic bacteria that live in the nodules of leguminous plants such as peas and beans and fixes the Atmospheric nitrogen into nitrates and nitrites

Option D:

Pseudomonas: It is denitrifying bacteria that reduce the nitrate into nitrogen.

The final answer is option A.