Abstract
Little is known about evolutionary drivers of microbial populations in the warm subseafloor of deep-sea hydrothermal vents. Here we reconstruct 73 metagenome-assembled genomes (MAGs) from two geochemically distinct vent fields in the Mid-Cayman Rise to investigate patterns of genomic variation within subseafloor populations. Low-abundance populations with high intra-population diversity coexist alongside high-abundance populations with low genomic diversity, with taxonomic differences in patterns of genomic variation between the mafic Piccard and ultramafic Von Damm vent fields. Populations from Piccard are significantly enriched in nonsynonymous mutations, suggesting stronger purifying selection in Von Damm relative to Piccard. Comparison of nine Sulfurovum MAGs reveals two high-coverage, low-diversity MAGs from Piccard enriched in unique genes related to the cellular membrane, suggesting these populations were subject to distinct evolutionary pressures that may correlate with genes related to nutrient uptake, biofilm formation, or viral invasion. These results are consistent with distinct evolutionary histories between geochemically different vent fields, with implications for understanding evolutionary processes in subseafloor microbial populations.
Highlights
Little is known about evolutionary drivers of microbial populations in the warm subseafloor of deep-sea hydrothermal vents
Examination of genomic variation within microbial populations can provide insights into the evolutionary and ecological factors that drive diversification, but few studies have focused on genomic variation of microbial populations in the deep sea, despite the fact that the subseafloor is a unique environment for the study of evolution due to its extreme habitats, variations in dispersal rates, metabolic innovation, and novel taxa[17, 18]
The sample temperatures ranged from ~18 °C to 140 °C, with magnesium concentrations ranging from 14–53 mmol/kg, reflecting the high variability in mixing of seawater with hydrothermal fluid in the subseafloor
Summary
Little is known about evolutionary drivers of microbial populations in the warm subseafloor of deep-sea hydrothermal vents. Comparison of nine Sulfurovum MAGs reveals two high-coverage, low-diversity MAGs from Piccard enriched in unique genes related to the cellular membrane, suggesting these populations were subject to distinct evolutionary pressures that may correlate with genes related to nutrient uptake, biofilm formation, or viral invasion These results are consistent with distinct evolutionary histories between geochemically different vent fields, with implications for understanding evolutionary processes in subseafloor microbial populations. End member hydrothermal fluids at Von Damm are less acidic, contain lower levels of dissolved sulfide, and have substantially higher concentrations of dissolved hydrocarbons relative to Piccard[27, 28, 30] These geochemical differences appear to strongly influence microbial community structure. By examining of patterns of fine-scale genomic variation within and between populations, we show that
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