Nitrogen fixation is the incorporation of atmospheric nitrogen into ammonia by various bacteria, catalyzed by nitrogenase.This is an essential stage in the nitrogen cycle and is the ultimate source of all nitrogen in living organisms. Nitrogen cycle: atmospheric nitrogen is inert and cannot be used by living forms
Nitrogen fixation is a chemical process by which molecular nitrogen in the air is converted into ammonia or related nitrogenous compounds in soil or aquatic systems. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms.