Abstract
SummaryThe structure and function of microbial communities inhabiting the subseafloor near hydrothermal systems are influenced by fluid geochemistry, geologic setting and fluid flux between vent sites, as well as biological interactions. Here, we used genome‐resolved metagenomics and metatranscriptomics to examine patterns of gene abundance and expression and assess potential niche differentiation in microbial communities in venting fluids from hydrothermal vent sites at the Mid‐Cayman Rise. We observed similar patterns in gene and transcript abundance between two geochemically distinct vent fields at the community level but found that each vent site harbours a distinct microbial community with differing transcript abundances for individual microbial populations. Through an analysis of metabolic pathways in 64 metagenome‐assembled genomes (MAGs), we show that MAG transcript abundance can be tied to differences in metabolic pathways and to potential metabolic interactions between microbial populations, allowing for niche‐partitioning and divergence in both population distribution and activity. Our results illustrate that most microbial populations have a restricted distribution within the seafloor, and that the activity of those microbial populations is tied to both genome content and abiotic factors.
Highlights
First discovered in 1977, deep-sea hydrothermal vents host flourishing ecosystems that are fuelled by chemosynthetic microbes
Despite commonly observed differences in microbial community structure at various hydrothermal systems in distinct geological settings, the functional repertoire of microbial communities is sometimes more similar across hydrothermal systems than their taxonomic composition might imply. This was recently observed at the Mid-Cayman Rise, located on an ultraslow spreading ridge in the Caribbean Sea, where two distinct types of vent systems exist: the mafic Piccard vent field, which is the deepest vent site discovered to date at a depth of 4960 m, and the ultramafic Von Damm vent field, located 20 km away on top of a massif at 2350 m depth (German et al, 2010)
Metagenomic analyses of one sample from each site showed that a wider diversity of metabolisms was observed at Von Damm, including anaerobic methane oxidation, the microbial communities at the two vent fields had near functional equivalence, with metabolisms related to methane, hydrogen, and sulphur cycling
Summary
First discovered in 1977, deep-sea hydrothermal vents host flourishing ecosystems that are fuelled by chemosynthetic microbes. Despite commonly observed differences in microbial community structure at various hydrothermal systems in distinct geological settings, the functional repertoire of microbial communities is sometimes more similar across hydrothermal systems than their taxonomic composition might imply. This was recently observed at the Mid-Cayman Rise, located on an ultraslow spreading ridge in the Caribbean Sea, where two distinct types of vent systems exist: the mafic Piccard vent field, which is the deepest vent site discovered to date at a depth of 4960 m, and the ultramafic Von Damm vent field, located 20 km away on top of a massif at 2350 m depth (German et al, 2010). The authors hypothesized that these similarities in functional repertoire likely result from the high concentrations of both hydrogen and sulphide available at both sites (McDermott et al, 2015, 2018; Reveillaud et al, 2016)
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