Microbial Diversity Of Sediments And Sulfide From Hydrothermal Vent And Their Importance In The System

Hydrothermal vent was discovered in 1979, and its discovery improved our understanding about lives. Because the hydrothermal vent plume including kinds of chemicals and enormous energy, and a lot of life-form were brougnt up. Many of them are pizotrophic and hyperthermophilic and can decompound noxious gases. This mechianism is different with our understanding about lives on the world. Many scientists think the environments of hydrothermal vent are similar with that when the lives appeared first on the earth. The study towards the deep-sea microbes will be helpful to the understanding of the origin of life, the character of biodiversity and to the exploitation of microbial resources in deep sea. The metabolic and ecological study of life on hydrothermal vent environments will give some insights on evolution and adaptation mechanism of extremophiles.Ammonia-oxidizing archaea was dicovered in 2005. For a long time,β-andγ-proteobacteria were thought as the most important microbial, and studied as a amodel. But in 2005, scientists screened a fosmid clone contained a 16S rRNA gene of group 1.1b Crenarchaeota alongside genes encoding potential homologues of Bacterial AMO A and B subunits. The ultimate confirmation of AOA was achieved by cultivation of a mesophilic Crenarchaeota from a marine aquarium in Seattle, USA. This Crenarchaeota strain grows chemolithoautotrophically and uses ammonia as the sole energy source. It further raises the questions,for example, are there any AOA in other microbial system? What's their diverisity and ubiquity? Which play more important role in ammonia oxidation, AOA or AOB? What's kind of arhaea has the capability oxidizing annomina?Here, we studied 3 sulfide chimneies obtained by Atlantic/Alvin in the fall of 2005 from Juan de Fuca Ridge and 15 sediments from Middle Atlantic Ridge, East Pacific Ridge and India Ridge obtained by"Dayang number 1"in the same year. We reported here the diversity, ubiquity and quatitative of ammonia-oxidizing archaea in the 18 samples. 2 sulfide rocks and 1 sediment core were analyzed through mcrA gene survy.The results of diversity of AOA-amoA survey on sulfide from hydrothermal vent indicated the diversity and richness was not high, but some differential AOA-amoA sequences were derived. Low temperature sample had high richness and diversity, and high temperature has low richness and diversity. All the sequences from sulfide defined to 2 groups: Chinmney Group I and Chimney Group II. The 2 groups had observed differences and the average similarity between the 2 groups was 80%. Chimney Group I had the closest relationship with the sediment A-1 cluster from Janpan Sea (94%). The Chimney Group II had low similarity with sequences deposited in NCBI (≦89%) which indicating this group was a new cluster, and maybe the differential ammonia oxidizing arhaea habited in hydrothermal vent system.In order to derive the possible origin of the new defined cluster, an archaeal 16S rRNA library was constructed. The analysis indicated only hyperthermophilic Crenarchaeota including Desulfococcas, Thermoproteas, were detected, but no Marine Group I existed. Assuming that one AOA cell contains only one copy of amoA genes, the AOA occupies at least 6% of the archaeal community. This large proportion of AOA should be easily detected by 16S rRNA library analysis. So,we think the AOAs don't related to MG1.Another results of diversity of AOA-amoA survey on sediments from hydrothermal vent field indicated the diversity and richness was high and the sequences obtained had closest relationship with deep-sea sequences, which indicated the similar origin of hydrothermal vent sediments and deep-sea sediments. The survey on archaeal 16S rRNA indicated all the sequences derived from hydrothermal vent sediments fall in MG1 group, which suggested ammonia-oxidizing archaea may belong to MG1. Comparison the sediments from hydrothermal vent and the sediment from West Pacific, the great difference was sequences didn't fall in the same OTUs and some sequences from West Pacific fall in Marine Bethic Group, which suggested there are diffrences between hydrothermal vent sediments and other kind of sediments.Fluorescence PCR used to quantitative the quantity of archaeal 16S rRNA, AOA-amoA and AOB-amoA gene. The results indicted a high value of AOA-amoA genes existed in the hydrothermal vent sediments and AOB-amoA genes were same or many times lower than AOA-amoA genes, which suggested AOA play important role in the environments of hydrothermal vent sediments. The quantity of archaeal 16S rRNA was between 4.598×10⁴copies/dry g～7.027×10⁷copies/dry g, AOA-amoA gene quantity was between 4.597×10⁴ copies/dry g～6.701×10⁶ copies/dry g , and AOB-amoA genes quantity was between 1.182×10⁴ copies/dry g～2.302×10⁶ copies/dry g. The ratios of AOA-amoA to AOB-amoA was between 0.75～170. Correlation analysis indicated there were significant correlation bween arhcaeal 16S rRNA and AOA-amoA gene (r=0.652,n=16,P﹤0.01). Significant (P﹤0.01) or positive correlations(P﹤0.05)were found between archaeal amoA gene copies number and organic matters (organic carbon and organic nitrogen), mineral nitrogen, total nitrogen, concentrations of NH₄⁺,NO₃^-,NO₂^-, PNR, pH and similar correlations were found between bacterial amoA gene copies number and chemical or PNR except no positive correlations were found between organic carbon and nitrogen. Significant correlation between archaeal amoA gene copies number and bacterial amoA gene copies number was found from 12 sites, and positive correlation found from the other 4 sites.Inadditional, we investigated the microbial related to methano by constructing mcrA gene clone libraries of sulfide and Mexico sediments. The results indicated methanogenic archaea were predominant in sulfide, which surrounded by high concentration of H2 and CO2, and methano-oxidizing archaea (MOA) were predominant in Mexico Gulf sediment.Our study gave some explanations of the questions about ammonia-oxidizing arhaea, which will improve the study on this metabolize, and hydrothermal vent chimneys and sediments were used in the thesis, which is helpful for the discovery of this microbial system.