Bcterial Diversity Of Deep-sea Sediments From The East And West Pacific Ocean

Due to the special environment characteristics of the deep-sea such as cold, high pressure, dark and poor organic carbon, the biosphere in the deep-sea environments was markedly different from the continent and the shallow sea. In addition, because of the rich abundance and special metabolism pathways of microorganisms inhabiting in the deep-sea environments, the deep-sea has been considered as an important reservoir of biological resources for exploration.The sediment samples used in this study were collected from the E272 site in the East Pacific Ocean (12°36'39"N, 104°19'28"W) and the Ph05-5 site of the West Pacific Ocean (16°04'93"N, 124o34'48"E). The E272 site was 45 km from the East Pacific Rise 13°N at a depth of 3 191 m. The Ph05-5 site at a depth of 3 382 m was situated at the headstream area of Kuroshio in the West Philippine Basin and was in the margin area of the West Pacific warm pool. This sediment core recovered from the Ph05-5 site was mainly composed of pelagic clay and five buried volcanic layers.Fine-scale bacterial vertical distribution of the 40cm depth sediment core recovered from the E272 site in the East Pacific Ocean were investigated by using methods of T-RFLP and 16S rRNA gene clone library analyses. Cluster analyses of T-RFs showed that bacterial phylotypes shifted with depth even in 40 cm sediment. Diversity of bacteria was detected in this sediment environment and at least 9 major lineages of the bacteria domain were obtained. They are the phyla of the Proteobcteria, Planctomycetes, Actinobacteria (high G+C Gram-positive bacteria), Bacteroidetes, Chloroflexi, Acidobacteria, Nitrospirae, and candidate division OP8, candidate division TM6. The division of the Proteobcteria contained three subdivisions including theα-,γ- andδ-Proteobateria subdivisions in our libraries and the Proteobcteria bacteria were common in different deep-sea environments. The analyses indicated the relatively high diversity of bacteria in this sediment environment and the shift of bacterial communities with depth should also indicate changes of physichemical properties on fine scale of sediments close to surface.The bacterial community of the sediment samples collected from the Ph05-5 site of the West Pacific Ocean was also analyzed by using the 16S rRNA gene clone library analysis method. Phylogenetic analyses showed that the diversity of the bacteria obtained from this sediment core was low comparatively. There were 6 phyla obtained from our libraries including the phyla of Proteobcteria, Planctomycetes, Actinobacteria (high G+C Gram-positive bacteria), Firmicutes (low G+C Gram-positive bacteria), Chloroflexi, and Acidobacteria. Three subdivisions of the Proteobcteria division including the subdivisions of theα-,γ- andδ-Proteobateria were also detected in this sediment core. Cluster analysis and phylogenetic analyses both showed that the bacterial communities occurring in the surface layer were markedly different from the other eight deeper layers and there were no obvious differences of the communities presenting in the deeper 8 layers including 3 pelagic clay layers and five buried volcanic ash layers. The discovery indicated that the volcanic ash dispersed in deep-sea sediment would not only affect the microbial community inhabiting in the volcanic ash layers but would influence the whole sediment due to the diffusion of volcanic ash materials along with the burial times. It was possible that due to the sedimentation time of the sediment surface layer was later than the deeper layers, the bacterial community was influenced by the volcanic ash materials less than the other deeper layers or due to the differerent physiochemical properties of the sediment surface with the deeper layers, the bacterial community in surface layer were special.Compare analyses of the bacterial diversity of the two deep-sea sediment cores recovered from the East Pacific Ocean and the West Pacific Ocean as well as bacterial diverisity in other sediment environments showed that the Proteobactia phylum bacteria were common in different deep-sea environments. The analyses also indicated that there were marked differences of bacterial communities between the samples recovered from the East Pacific Ocean and the West Pacific Ocean. The bacterial diversity of the East Pacific Ocean sediment was higher than the bacterial diversity of the West Pacific Ocean sediments. It is possible that the volcanic ash materials dispered in sediment recovered from the West Pacific Ocean was a major influence factor. In addition, the different environment characteristics of different Ocean may be an important factor too.