Characteristics Of Bacterial Community In The Sediments Of Bohai And Yellow Seas,Revealed By 454-pyrosequencing

Marine microorganism, as an important participator of various biogenic elements circulation and transformation, plays a crucial role in controlling global biogeochemical cycles. Researching microbial community structure and diversity and their response to environmental factors could provide us a better understanding on biogeochemical processes, which may also lay a foundation for studies on marine ecology. At present study, bacterial community structure and diversity and the relationships between environmental elements and bacterial community composition in the Bohai and Yellow Seas were explored by High-throughput sequencing (454-Prosequencing).Bacterial community structure and diversity in 19 surface sediment samples of the Bohai and Yellow Seas were investigated. Totally,124147 optimized reads with the average length of 395 bp in V4-V6 region of 16S rRNA were obtained. Generally, aligning to the SILVA database found that there were 58 phyla,160 classes,294 orders,440 families and 770 genera. Each taxonomic category exist some unclassified information. The proportion increased from phylum level to genus level, ranging from 36.2-67.4%. The dominant taxa at the phylum level in the Bohai and Yellow Seas were Proteobacteria, Acidobacteria, Verrucomicrobia, Actinobacteria, Bacteroidetes, Nitrospira and Gemmatimonadetes. There was non-significant difference at the phylum level (p>0.05). Deltaproteobacteria, Gammaproteobacteria, Betaproteobacteria, Alphaproteobacteria, Acidimtcrobiia, Verrucomicrobiae, Thermoleophilia and Nitrospira were some dominant classes. Deltaproteobacteria and Gammaproteobacteria were the dominant taxa in the whole research field, proportion ranging between 24% at the estuary area and 70% at the central of Bohai and Yellow Seas. Betaproteobacteria (17-21%) and Thermoleophilia (6-7%) mainly inhabited at the estuary area. The unclassified information in Shuangtaizi River and Yellow River (33%) was relatively higher than that in the central of Bohai and Yellow Seas (13%).The Shannon-Weaner index ranging from 3.32-9.24 (ave.7.86) and Chao I index fluctuated from 887-3673 (ave.2088), both of which were lower nearby Bohai strait than other sampling stations. The cluster analysis revealed that samples from the similar environment tend to cluster together. Such as, in Shuangtaizi River and Yellow River harbored certain bacterial lineages that differentiated it from other habitats in the Bohai and Yellow Seas (p<0.05). Statistical analysis showed that organic carbon (OC), total nitrogen (TN) and total phosphorous (TP) had significant correlation with Shannon index (H’),correlation coefficients were 0.513,0.468 and 0.554, respectively, however, non-significant with richness index. CCA was applied to explore the relationship between salinity, pH, MD, TN, TP, OC, Chl a and bacterial community structure. The results showed that OC (0.756,p<0.05), TN (0.697,p<0.05), TP (0.705, p<0.05), salinity (-0.512,p<0.05) and pH (-0.531, p<0.05) were the main elements in regulating bacterial community structure. Nonetheless, the main factors were not the same in the Bohai and Yellow Seas. Shortly, Samples collected form Shuangtaizi River and Yellow River were mainly affected by OC, while TN and TP were the factors in influencing bacterial community of Bohai central and the North Yellow Sea. And Jiaozhou Bay and Laizhou Bay were controlled by salinity and pH separately.