the diversity of the diazotrophs in the South China Sea. uncultured marine microorganism

We used 454 pyrosequencing of the nifH gene to study seasonal dynamics of diazotrophic communities in South China Sea. The results show that the diazotrophs in South China Sea are almost clustered in cluster I, including Cyanobacteria and Proteobacteria. The anaerobes (cluster II) and methanogens (cluster III) clusters are rare and mainly distributed in the middle and lower surface layer. In the diazotrophic communities, the Proteobacteria, especially the γ-Proteobacteira is predominant. In the middle and lower surface layer, the diazotrophs were almost Proteobacteria. Its contribution to marine nitrogen fixation is worth further consideration. Among the cyanobacterial diazotrophs, the Trichodesmium species were most abundant and the proportion of unicellular cyanobacterium group A, B, C and the diatom symbiont Richelia were rare. In the South China Sea, the structure of diazotrophic communities was stable, and the γ-Proteobacteira and Trichodesmium were the dominant diazotrophic groups. Combined with the data of previous studies, it was showed that the surface water temperature may be one of the main factors determining the community structure of marine nitrogen-fixing microorganisms.