Characterization of microbial communities in sediments of the South Yellow Sea

Illumina sequencing and quantitative PCR (qPCR) based on the 16S ribosomal RNA (rRNA) gene were conducted to characterize the vertical distribution of bacterial and archaeal communities in the sediments of two sites from the South Yellow Sea. Both bacterial and archaeal communities showed a clear stratified distribution with sediment depth. The microbial communities in the upper layers were distinct from those in the deeper layers; the relative abundances of sequences of Thaumarchaeota, Gammaproteobacteria, and Actinobacteria were higher in the upper than in the deeper sediments, whereas the sequences of Bathyarchaeia, Lokiarchaeota, Euryarchaeota, Chloroflexi, and Deltaproteobacteria were relatively more abundant in the deeper sediments. Sediment depth and total organic carbon (TOC) can significantly influence both the bacterial and archaeal communities. Furthermore, bacterial and archaeal groups potentially involved in nitrogen, sulfur, and methane metabolism were detected in both sites. In our study, both ammonia-oxidizing bacteria (Nitrospira) and ammonia-oxidizing archaea (Candidatus Nitrosopumilus) were responsible for ammonia oxidization. Additionally, sulfur-reducing bacteria SEEP-SRB1 forming consortia with anaerobic methane-oxidizing archaea ANME-2a-2b were capable of anaerobic methane oxidation (AOM) in the 3400-02 sediment samples.