High-throughput sequencing reveals the main drivers of niche-differentiation of bacterial community in the surface sediments of the northern South China sea.

Studies on marine bacterial communities have revealed endemism in local communities, yet the underlying mechanisms remained elusive. Environmental gradient settings can benefit the straightaway study of community composition changes and the mechanisms explaining them. Here, MiSeq-based 16S rRNA gene sequencing was performed on 12 surface sediment samples from the northern South China Sea (nSCS) revealing that shallow-sea samples had a higher alpha diversity than deep-sea samples, and were differentiated from them significantly based on beta diversity. Temperature, seawater depth, and salinity were the top three influential factors. Bacterial 16S rRNA gene abundance was positively correlated with temperature, and negatively correlated with salinity. Sulfate-reducing bacteria including Desulfobacteraceae, Desulfobulbaceae, and Syntrophobacteraceae were enriched in shallow-sea sediments, co-abundant with nitrite-oxidizing Nitrospira and potential sulfur-oxidizing shallow-sea specific Woeseiaceae/JTB255 clade. Meanwhile, the co-existing and co-abundant of marine anammox and n-damo bacteria were enriched in deep-sea sediments, which was firstly evidenced in this study. The global deep-sea cosmopolitans, OM1 clade, and deep-sea specific Woeseiaceae/JTB255 clade were also found enriched in deep-sea sediments of nSCS. The discovery of novel taxa which were differentially enriched in shallow-/deep-sea sediments not only shed light on enigmatic physiological properties and the natural selection mechanism, but also provided the potential ecological-functional links which invoked further genomics-based metabolic characteristics.