Which microorganism converts ammonia nitrogen to nitrite?

The conversion of ammonia nitrogen to nitrite is primarily carried out by Nitrosomonas, which is a genus of bacteria known for its role in the nitrogen cycle, particularly in the process of nitrification. During this process, Nitrosomonas oxidizes ammonia (NH3) to nitrite (NO2-). This reaction is crucial in wastewater treatment because it helps in the removal of toxic ammonia from the environment, converting it to less toxic forms.

In the context of the nitrogen cycle, this step is essential as it prepares for the subsequent conversion where nitrite is further oxidized to nitrate (NO3-), mainly by bacteria such as Nitrobacter. Understanding the specific roles of these microorganisms is vital for managing waste treatment processes effectively. While other bacteria mentioned, such as Escherichia coli and Aeromonas, play roles in other aspects of wastewater treatment, they do not specialize in the conversion of ammonia to nitrite.