Existence and distribution of novel phylotypes of in water columnsof the South China Sea.

In the biological nitrogen cycle, nitrite oxidation is performed by nitrite oxidation bacteria, of which is widespread and diverse. Communities of were collected at 25-1500 m depths in the South China Sea. Phylogenetic diversity, community composition, and environmental factors were investigated using high-throughput sequencing targeting the B gene and statistical analyses. The community composition of varied spatially and by depth. Among the 24 OTUs with relatively high abundance, 70% were unclassified and not affiliated with the known genus, suggesting a previously unrecognized high diversity of marine . Five known genera were detected, of which the common marine was not the dominant species, whereas and dominated in shallow habitats. Comammox Nitrospira nitrosa was discovered in the marine ecosystem. The niche differentiation of versatile species was mainly shaped by nitrate, temperature, and DO.