Microbial Diversity Of Sediment In Deep-sea And Their Roles In The Deep Sea

The sediment samples used in this study were collected from the west Pacific Warm Pool, east Pacific nodule province and middle regions of the tropical Pacific Ocean with water depth from 1914m to 5774m by cruises "DY105-11", "DY105-13" which was organized by China Mineral Resources Association.49 isolates, which were obtained from the sediment samples from west Pacific Warm Pool and east Pacific nodule province, were analyzed in this study. Most isolates belong to cold-tolerance bacteria and can grow from 0℃ to 30℃ . Some alkaline-tolerance bacteria were also isolated from the sediment but no acid-tolerance. The molecular classification and identification of these isolates based on the 16S rDNA sequences indicated that the Halomonas sp. and Psychrobacter sp. were dominant groups in the sediment sample from west Pacific Warm Pool; Halomonas sp. and Pseudmonas sp. were the dominant groups from those of east Pacific nodule province.Two pizophilic strains (wp2 and wp3) which belong to Shewanella genus were isolated from the west Pacific Warm Pool in this study. Specific bands for the pressure regulated operons could be amplified from the total DNA of WP2 and WP3. The DNA sequences of the amplified fragments of WP2, WP3 show high similarity with the sequences of operons of S.benthica and S.Voilacea (77%-90%, 89%-94% respectively). Substantial amount of Eicosapentaenoic acid (EPA, 20:5) were found both in WP2 and WP3. The EPA composition increased dramatically when the growth temperatures were decreased and reached highest at 0℃. All these results strongly suggested that they were piezophilic Shewanella strains. 16S rDNA sequence analysis and DNA-DNA hybridization results suggested that WP2 and WP3 were two new Shewanella species.The profile of sediments from west Pacific Warm Pool was evaluated by culture-independent molecular phylogenetic methods. The investigation on bacteria indicated the γ -proteobacteria was dominant in the west Pacific Warm Pool. The biomass of bacteria in this area was 10 to 100 low than that of the soil in the land. Theinvestigation on archaea showed that the Crenarchaeota was privilege in the west Pacific Warm Pool. All these crenarchaeotal clones except for two clones belong to marine group I (MGI), which were ubiquitous in marine environments, from the surface to the bottom of waters, deep-sea sediments. The MGI clones detected show high similarity with environmental clones from various part of the ocean, indicating that the MGI members in the deep sea may have a common ancestry. The abundances of archaea were 102"3cell/g sediment in the five sites of the west Pacific Warm Pool. The biomass of archaea was increased (from 102 to 105cell/g sediment) when the depth was increased in the site wpO.The specific primers for the microbes involving in the metabolic of CH4 production, CH4 oxidation and sulphate reduction were used to evaluated the interaction between microorganisms and environment. The investigation based on the MxaF gene indicated the Mythylotrophs and typell Methanotrophs were distributed in the west Pacific Warm Pool and the biomass was 10-100 higher than that in the east Pacific nodule province and middle regions of Pacific. No specific bands were obtained from the west Pacific Warm Pool by the specific primers for methanogen groups. A group of novel archaea (WPA) was revealed by the selective primers for methane oxidization archaea (MOA). One subgroup of them (WPAII) could be placed in the Euryarchaeota kingdom and was peripherally related with methanogens and MOA. WPA only constituted a small proportion of the archaea community (0.05% to 5%) in west Pacific Warm Pool sediment. Clones peripherally related to Desulfuromonas, Desulfacinum, Desulfonauticus and Desulfomonile were revealed by the primers selectively for sulphate reducing bacteria. The biomass of this group of bacteria in west Pacific Warm Pool was 10 higher than that of east Pacific nodule province.These results indicated that there was an intact cycle that coupled sulfur metabolism with methane metabolism existing in the west Pacific Warm Pool. The metabolic activity in this area was higher than that of other areas in open ocean.Tropical west Pacific Warm Pool is a geological important area which is fundamental to the climate of the earth. Our investigation of microbial diversity in deepsea sediment would be helpful to evaluate the role of the microbes in the cycling of material on the earth.