Question

The fixation of free nitrogen by bacteria in the soil is done by

• A. Azotobacter
• B. Nitrosomonas
• C. Nitrobacter
• D. Thiobacillus

Answer 1

The correct option is A Azotobacter

Nitrogen fixation is the process of fixation of free nitrogen from the atmosphere. This is done by symbiotic bacteria like Rhizobium. They are in symbiotic association with the the root nodules. They provide nitrogen to the plant. In return, they get shelter from the plant. Azotobacter are free living nitrogen fixing bacteria. They fix the atmospheric free nitrogen in the soil.

Thus, the correct answer is 'Azotobacter.'