Question

Which of the following is non-symbiotic nitrogen fixer organism?

• A. VAM
• B. Azotobacter
• C. Rhizobium
• D. Anabaena

Answer 1

Answer: (B)

• Azotobacter is a free-living obligate aerobic rod-shaped soil bacteria. It fixes the atmospheric nitrogen which is inaccessible to the plants into the soil.
• It does not reside in the roots of the plant. It remains in the soil and converts the atmospheric nitrogen into the soluble form, ammonium ions.
• It has the unusual ability to fix atmospheric nitrogen as it produces nitrogenase enzyme and convert it to ammonia.

Thus, the correct answer is option B.