Question

An anaerobic bacterium capable of nitrogen fixation is

• A. Chlorobium
• B. Rhodospirillum
• C. Clostridium
• D. All of the above

Answer 1

The correct option is D All of the above

Reduction of inert atmospheric nitrogen to ammonia by living organisms is called biological nitrogen-fixation. Only certain prokaryotic organisms (some bacteria and cyanobacteria) are capable of fixing $N_2$. Such microbes are called $N_2$-fixers. These $N_2$-fixing microbes contain an exclusive enzyme, Nitrogenase that is capable of reducing nitrogen. The nitrogen-fixing microbes could be free-living or symbiotic in nature. Chlorobium, Rhodospirillum and Clostridium are anaerobic, free-living, $N_2$-fixing bacteria.