Ecological distribution and function of comammox Nitrospira in the environment

Complete ammonia oxidizers (Comammox) are of great significance for studying nitrification and expanding the understanding of the nitrogen cycle. Moreover, Comammox bacteria are also crucial in natural and engineered environments due to their role in wastewater treatment and maintaining the flux of greenhouse gases to the atmosphere. However, only few studies are there regarding the Comammox bacteria and their role in ammonia and nitrite oxidation in the environment. This review mainly focuses on summarizing the genomes of Nitrospira in the NCBI database. Ecological distribution of Nitrospira was also reviewed and the influence of environmental parameters on genus Nitrospira in different environments has been summarized. Furthermore, the role of Nitrospira in carbon cycle, nitrogen cycle, and sulfur cycle were discussed, especially the comammox Nitrospira. In addition, the overviews of current research and development regarding comammox Nitrospira, were summarized along with the scope of future research. KEY POINTS: • Most of Comammox Nitrospira are widely distributed in both aquatic and terrestrial ecosystems, but it has been studied less frequently in the extreme environments. • Comammox Nitrospira can be involved in different nitrogen transformation process, but rarely involved in nitrogen fixation. • The stable isotope and transcriptome techniques are important methods to study the metabolic function of comammox Nitrospira.