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In the dark ocean primary production is carried out by chemolithoautotrophic microorganisms, with the oxidation of reduced sulfur compounds being a major driver for microbial carbon fixation. At highly sulfidic hydrothermal fields a variety of microorganisms oxidizing sulfur compounds can be observed in high abundance. Yet, the principles of niche differentiation and distribution of the different sulfur-oxidizing prokaryotes (SOP) across geochemical gradients remain poorly understood.We addressed niche differentiation of SOP by extensive sampling of active sulfidic vents at six different hydrothermal venting sites in the Manus Basin, in Papua New Guinea. For this study, we collected 33 diffuse fluid and rising plume samples, and 23 samples from surfaces of chimneys, rocks and fauna. Based on our detailed analyses of 16S RNA gene sequences, metagenomes and real-time in situ measured geochemical parameters, we are now able to describe the distribution and potential niches of SOP from the highly diverse Epsilonproteobacteria genera Sulfurimonas and Sulfurovum and the rather uniform SUP05-clade Gammaproteobacteria within the geochemical mixing gradient. While Sulfurovum was mainly found attached to surfaces exposed to diffuse venting, the SUP05-clade was found to be planktonic in areas of high dilution of the vent fluids by entrained seawater. We further propose that the high diversity within Sulfurimonas and Sulfurovum related bacteria observed in this study derives from the high variation of environmental parameters such as sulfide concentrations across small spatial and temporal scales within their niche. |