Analysis About The Diversity Of Cultivable Bacteria In Northern South China Sea And Polyphasic Taxonomic Research On Two Strains Isolated From The Deep Seawater

The South China Sea(SCS)located in the Northwest Pacific is not only the world's third-largest marginal sea,but also the largest sea in China.It belongs to biological hot spots of marine systems and is considered to possess the world's highest level of species diversity.Due to its special geographic location,many different countries were built around it and complicated international relations formed with each other.Although the SCS is rich in microbial resources,fewer reports appeared in the international academic researches,and they were largely confined to focus on surface water,sediments or symbionts such as sponges in the SCS.There is never relative research about bacterial diversity and community structure from the surface to the deep sea.In this research,the cultivable method was measured and the seawater in northern South China Sea(nSCS)was targeted to study the microbial diversity analysis and community structure,including 0 m,and 100 m,and 200m,and 300 m,and 500 m,and 1,000 m,and 1,400 m and 2,500 m at eight different depths,classified into three layers such as Surface Layer,Mesopelagic Layer and Bathypelagic Layer or Deep Layer.The whole research was systematically studied and extended the depth to the deep sea in layer in order to find out and compare microbial resources in the SCS.In the meanwhile,two strains isolated from the Bathypelagic Layer 2,500m were identified by polyphasic taxonomy study in order to determine its taxonomic status.Firstly,eight seawater samples at different depths were diluted on the culture medium agar plates and then cultured for 2-4 weeks by the cultivable method.As a result,202 microbial strains were isolated from these samples,which were identified into 80 species and 58 genra.Besides,17 of these strains were suspected to be new species.From the perspective of the whole nSCS,Alphaproteobacteria dominated the isolated bacteria,Actinobacteria followed.Bacteroidetes and Firmicutes were the least.Secondly,two strains,HSF7T and HSF11T,which were isolated from 2,500 and owned the low 16S rRNA gene similarity(less than 97%),were identified by polyphasic taxonomy method.Finally,strain HSF7T was identified as a new species of genus Thalassobaculum in family Rhodospirillaceae,named as Thalassobaculum fulvum.And strain HSF11T was identified as a new genus in family Rhodobiaceae,named as Microbaculum marinum.Apart from being beneficial to find and identify a wide variety of microbial resources in nSCS and helping to make a preliminary preparations for understanding the microbial community structure in nSCS,the research above will lay the foundation for perfecting evolutionary science and be conducive to the future development and application of marine resources.