Question

which of these is a free living aerobic and anaerobic nitrogen-fixing bacteria respectively?

• A. Rhizobium, Clostridium
• B. Azotobacter, Clostridium
• C. Azotobacter, Agrobacterium
• D. Agrobacterium, Clostridium

Answer 1

The correct option is B Azotobacter, Clostridium

The bacteria that convert atmospheric nitrogen into utilisable compounds of nitrogen like nitrate, ammonia, etc. are known as nitrogen-fixing bacteria. They possess nitrogenase enzyme which helps them in nitrogen fixation. These bacteria are either free-living or in symbiotic relationship with roots of the plants.

Azotobacter and Clostridium are free-living nitrogen-fixing bacteria. Azotobacter is aerobic because it can strictly live only in the presence of oxygen, whereas Clostridium is anaerobic because its growth is not strictly dependent on the presence of oxygen.