Occurrence and diversity of nitrite-dependent anaerobic methane oxidation bacteria in the sediments of the South China Sea revealed by amplification of both 16S rRNA and pmoA genes.

Nitrite-dependent anaerobic methane oxidation (n-damo) process is unique in linking the microbial carbon and nitrogen cycles, but the presence of n-damo bacteria in marine ecosystem and the associated environmental factors are still poorly understood. In the present study, detection of n-damo bacteria using 16S rRNA and pmoA gene-based PCR primers was successfully employed to reveal their diversity and distribution in the surface and subsurface sediments of the South China Sea (SCS). The widespread occurrence of n-damo bacteria in both the surface and subsurface sediments with high diversity has been confirmed in this study. The pmoA gene-amplified sequences clustered within three newly erected subclusters, namely SCS-1, SCS-2, and SCS-3, suggesting the unique niche specificity of n-damo bacteria in the marine ecosystem. Results indicated the presence of n-damo bacteria in the west Pacific Ocean with a wide distribution from the continental shelf (E201S) to the deep abyss (E407S and E407B). Community structures of n-damo bacteria in SCS are clearly different from those of nonmarine ones known. It is also found that NO x (-) and NH4 (+) affected the community structures and distribution of n-damo bacteria in the SCS sediments differently. Salinity is another important factor identified, shaping the n-damo communities in marine environments. The community based on pmoA gene-amplified sequences, and community richness and diversity based on 16S rRNA gene-amplified sequences correlated with temperature.