Comammox
Comammox, short for "complete ammonia oxidation," describes a recently discovered process performed by certain microorganisms where a single organism can completely oxidize ammonia (NH3) to nitrate (NO3-). This contrasts with the previously understood two-step process of nitrification, which was thought to require the coordinated action of two different groups of microorganisms: ammonia-oxidizing bacteria (AOB) or archaea (AOA), which oxidize ammonia to nitrite (NO2-), and nitrite-oxidizing bacteria (NOB), which oxidize nitrite to nitrate.
Comammox microorganisms are bacteria within the genus Nitrospira and possess the genetic machinery to carry out both steps of nitrification within a single cell. This discovery significantly altered the understanding of the nitrogen cycle and has implications for understanding nitrogen cycling in various environments, including wastewater treatment plants, soils, and aquatic ecosystems.
The identification of comammox bacteria has led to new research avenues exploring their ecological roles, distribution, and potential applications. Further research is ongoing to fully understand the diversity of comammox bacteria, the factors that influence their activity, and their contribution to global nitrogen cycling processes. The existence of comammox also prompts a re-evaluation of existing nitrogen cycle models and treatment strategies.