Abstract
Hydrothermal plumes transport reduced chemical species and metals into the open ocean. Despite their considerable spatial scale and impact on biogeochemical cycles, niche differentiation of abundant microbial clades is poorly understood. Here, we analyzed the microbial ecology of two bathy- (Brothers volcano; BrV-cone and northwest caldera; NWC) and a mesopelagic (Macauley volcano; McV) plumes on the Kermadec intra-oceanic arc in the South Pacific Ocean. The microbial community structure, determined by a combination of 16S rRNA gene, fluorescence in situ hybridization and metagenome analysis, was similar to the communities observed in other sulfur-rich plumes. This includes a dominance of the vent characteristic SUP05 clade (up to 22% in McV and 51% in BrV). In each of the three plumes analyzed, the community was dominated by a different yet uncultivated chemoautotrophic SUP05 species, here, provisionally named, Candidatus Thioglobus vadi (McV), Candidatus Thioglobus vulcanius (BrV-cone) and Candidatus Thioglobus plumae (BrV-NWC). Statistical analyses, genomic potential and mRNA expression profiles suggested a SUP05 niche partitioning based on sulfide and iron concentration as well as water depth. A fourth SUP05 species was present at low frequency throughout investigated plume samples and may be capable of heterotrophic or mixotrophic growth. Taken together, we propose that small variations in environmental parameters and depth drive SUP05 niche partitioning in hydrothermal plumes.
Highlights
Hydrothermal vents occur along oceanic spreading zones and volcanic arcs, in back-arc basins, and in intra-plate volcanoes
A microbial clade well known to inhabit hydrothermal sulfur-rich plumes, is the SUP05 clade within the Gammaproteobacteria [9]. Members of this diverse clade have successfully adapted to various lifestyles such as free-living organisms in plumes [8], oxygenminimum zones (OMZ) [10,11,12], pelagic redoxclines [13, 14] and as symbionts of clams, mussels and sponges [15,16,17]
The relationship between the microbial community and the Microbial communities were dominated by clades within the Alphaproteobacteria, Deltaproteobacteria and Gammaproteobacteria
Summary
Hydrothermal vents occur along oceanic spreading zones and volcanic arcs, in back-arc basins, and in intra-plate volcanoes At these sites, high-temperature fluids enriched in reduced chemical compounds vent from the seafloor and mix with ambient seawater until they reach a depth of neutral buoyancy. In addition to dark carbon fixation fueled by reduced sulfur compounds and hydrogen oxidation [18], SUP05 clade bacteria have been postulated to maintain a heterotrophic metabolism [19, 20]. Several representatives of this clade have already been cultivated and assigned to the genera Candidatus Thioglobus and Pseudothioglobus [21,22,23]. Despite the widespread occurrence and high diversity of this clade, the localization and niche partitioning of SUP05 in hydrothermal plumes has not yet been elucidated
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