Where do nitrogen fixing bacteria live and how to they create usable nitrogen?

Nitrogen-fixing bacteria primarily inhabit the root nodules of leguminous plants, as well as soil and water environments. They convert atmospheric nitrogen (N₂) into ammonia (NH₃) through a process called nitrogen fixation, using the enzyme nitrogenase. This ammonia can then be utilized by plants to synthesize essential organic compounds, making nitrogen accessible in a form that plants can absorb and use for growth. Some free-living nitrogen-fixing bacteria can also improve soil fertility independently of plant hosts.