Isolation And Diversity Of Sulfur Oxidizing-Bacteria In Deep Sea Of South Atlantic

The deep-sea hydrothermal system is one of the most extreme environments onEarth. With the discovery of hydrothermal vent in1977, it has been proposed thatreduced sulfur species of hydrothermal origin favor abundant microbial populations ofsulfur oxidizers, which can use H2S, element sulfur or thiosulfate as energy sources.More and more studies show that sulfur oxidation had been expected to be the primaryenergy metabolism driving deep-sea vent ecosystems.In this study, the diversity and physiology characters of microbes involved insulfur oxidization in hydrothermal vent environments were investigated based onmolecular ecology methods. The total10samples were collected from the SouthAtlantic during the22th cruise of “Da-Yang Yi-Hao” in2011.5, including hydrothermalsulfide samples and the nearby sediment samples. The SOB was enriched and isolatedwith sodium thiosulfate, elemental sulfur or hydrogen sulfide as electron donors, underaerobic, microaerobic (6%O2) and anaerobic conditions and different temperature,respectively. A Total of121bacteria were isolated and identified based on16S rRNAgene sequence analysis. The results showed that these isolates were closely related tothe published type strains (96.649%-100%), and belonged to28different genera, whilethe proteobacteria were the main group. The diversity of culturable bacteria isolatedfrom different medium is significantly different. Phylogenetic ananlysis indicated that11genus were obtained by using M1medium, Thalassospira and Citreicella are thedominant genus, accounting for23%and18%respectively; the isolates from M2medium clustered into7genus and Marinobacter accounted for45%, which is the maingroup; there is most diverse in the bacteria from M3medium, and Martelella werepredominant in18genus, accounting for16%; while there were7genus obtained fromM4medium and most of the bacteria belonged to Citromicrobium andNovosphingobium genus. BOX-PCR analysis the genetic diversity of the main isolatedbacteria species, while the bacteria of pseudomonas have large differences between thegenus, the differences of the other species is relatively small. The thermophilicanaerobic enrichments (4A3Y,4B3,7A3Y) were obtained. The diversity ananlysis indicated that Firmicute group was dominated in these enriched cultures. There is leastdiverse in enrichment culture4B3, only including3OTUs. The sequences retrievedform the enriched culture have the closet similarity to Caloranaerobacter azorensisMV1087、Desulfotomaculum halophilum SEBR3139and Hafnia paralvei ATCC29927.All strains isolated were evaluated whether they are chemolithothrophic bacteriawhich have the ability of assimilation of inorganic carbon. The RuBisCO (ribulosebisphosphate carboxylase)(formⅠand formⅡ) encoded by cbbL and cbbM gene whichis a key enzyme involved in the Calvin cycle were amplified; Combined withheterotrophic medium plate growth and the growth curve determination, some strainswith CO2fixation capacity or weak RuBisCO activity were found. Also the sulfuroxidation characteristics of the strains were analysed, the results based on the change ofpH value showed that most of the strains were the acid-producing SOB; The soxB gene,which is the key gene in Sox multienzyme system which catalyzes oxidation ofinorganic sulfur compounds, was amplified. The results indicated that only severalstrains belonged to Labrenzia have positive amplification. It is assumed that there werediverse soxB genes or it was the different sulfur metabolic pathway, such as reversesulfate reduction. The growth characteristics of strains under different concentrations ofsodium thiosulfate indicated that some strains which had not reported yet can bestimulated growth by sodium thiosulfate, including have the possibility function ofhydrocarbon degradation strains: Alcanivorax (strain L10M1-6), Sphingopyxis (strainL10M1-7) and Marinobacter (strain1A2-1and1A2-3), indicating their variedmetabolism. The metabolic diversity of these strains suggested it could be helpful forthem to adapt to hydrothermal area where both have hydrocarbon and hydrogensulphide generation.In short, the diverse and physiology characters of microbe involved in sulfuroxidization were investigated using different methods in the South Atlantic. Manyheterotrophic SOB have been isolated and identified. Sulfur metabolic pathways ofthese bacteria and their important role in sulfur cycle of hydrothermal vent enviromentsneed to be further study. Our study is the first important step to understand the ecological and biogeochemical roles of these sulfur oxidizer in deep-sea hydrothermalvent ecosystems.