Geologic map of the Samail Ophiolite, Oman and United Arab Emirates

A geologic map of the Samail Ophiolite in Oman and the United Arab Emirates has been georeferenced and digitized. The data are provided in GeoPackage (.gpkg) format that can be imported into GIS software such as QGIS and Arc. The GeoPackage contains vector layers for lithologies and faults. Five lithologies are represented: Dunite/Wehrlite, Harzburgite, Mafic, Metamorphic Sole, and Plagiogranite. Further, a QGIS project file is provided, which should allow for layer styles to be preserved if opened in QGIS. The map data (not georeferenced) were originally published as &nbsp; Nicolas, A., Boudier, F., Ildefonse, B., Ball, E., 2000. Accretion of Oman and United Arab Emirates ophiolite - Discussion of a new structural map. Mar Geophys Res 21, 147&ndash;179. doi:10.1023/A:1026769727917 &nbsp; Please cite both works if you use the georeferenced data. A GeoTIFF of the original Nicolas et al. map subdivided into greater lithological detail is also provided in the GeoPackage.</div

Parapatric speciation of Meiothermus in serpentinite-hosted aquifers in Oman

The factors that control the distribution and evolution of microbial life in subsurface environments remain enigmatic due to challenges associated with sampling fluids from discrete depth intervals via boreholes while avoiding mixing of fluids. Here, using an inflatable packer system, fracture waters were isolated and collected from three discrete depth intervals spanning &gt;130 m in a borehole intersecting an ultramafic rock formation undergoing serpentinization in the Samail Ophiolite, Sultanate of Oman. Near surface aquifer waters were moderately reducing and had alkaline pH while deeper aquifer waters were reduced and had hyperalkaline pH, indicating extensive influence by serpentinization. Metagenomic sequencing and analysis of DNA from filtered biomass collected from discrete depth intervals revealed an abundance of aerobes in near surface waters and a greater proportion of anaerobes at depth. Yet the abundance of the putatively obligate aerobe, Meiothermus, increased with depth, providing an opportunity to evaluate the influence of chemical and spatial variation on its distribution and speciation. Two clades of Meiothermus metagenome assembled genomes (MAGs) were identified that correspond to surface and deep populations termed Types I (S) and II (D), respectively; both clades comprised an apparently Oman-specific lineage indicating a common ancestor. Type II (D) clade MAGs encoded fewer genes and were undergoing slower genome replication as inferred from read mapping. Further, single nucleotide variants (SNVs) and mobile genetic elements identified among MAGs revealed detectable, albeit limited, evidence for gene flow/recombination between spatially segregated Type I (S) and Type II (D) populations. Together, these observations indicate that chemical variation generated by serpentinization, combined with physical barriers that reduce/limit dispersal and gene flow, allowed for the parapatric speciation of Meiothermus in the Samail Ophiolite or a geologic precursor. Further, Meiothermus genomic data suggest that deep and shallow aquifer fluids in the Samail Ophiolite may mix over shorter time scales than has been previously estimated from geochemical data

Intact polar lipidome and membrane adaptations of microbial communities inhabiting serpentinite-hosted fluids

The generation of hydrogen and reduced carbon compounds during serpentinization provides sustained energy for microorganisms on Earth, and possibly on other extraterrestrial bodies (e.g., Mars, icy satellites). However, the geochemical conditions that arise from water-rock reaction also challenge the known limits of microbial physiology, such as hyperalkaline pH, limited electron acceptors and inorganic carbon. Because cell membranes act as a primary barrier between a cell and its environment, lipids are a vital component in microbial acclimation to challenging physicochemical conditions. To probe the diversity of cell membrane lipids produced in serpentinizing settings and identify membrane adaptations to this environment, we conducted the first comprehensive intact polar lipid (IPL) biomarker survey of microbial communities inhabiting the subsurface at a terrestrial site of serpentinization. We used an expansive, custom environmental lipid database that expands the application of targeted and untargeted lipodomics in the study of microbial and biogeochemical processes. IPLs extracted from serpentinite-hosted fluid communities were comprised of &gt;90% isoprenoidal and non-isoprenoidal diether glycolipids likely produced by archaeal methanogens and sulfate-reducing bacteria. Phospholipids only constituted ~1% of the intact polar lipidome. In addition to abundant diether glycolipids, betaine and trimethylated-ornithine aminolipids and glycosphingolipids were also detected, indicating pervasive membrane modifications in response to phosphate limitation. The carbon oxidation state of IPL backbones was positively correlated with the reduction potential of fluids, which may signify an energy conservation strategy for lipid synthesis. Together, these data suggest microorganisms inhabiting serpentinites possess a unique combination of membrane adaptations that allow for their survival in polyextreme environments. The persistence of IPLs in fluids beyond the presence of their source organisms, as indicated by 16S rRNA genes and transcripts, is promising for the detection of extinct life in serpentinizing settings through lipid biomarker signatures. These data contribute new insights into the complexity of lipid structures generated in actively serpentinizing environments and provide valuable context to aid in the reconstruction of past microbial activity from fossil lipid records of terrestrial serpentinites and the search for biosignatures elsewhere in our solar system

Aqueous Geochemical and Microbial Variation Across Discrete Depth Intervals in a Peridotite Aquifer Assessed Using a Packer System in the Samail Ophiolite, Oman

The potential for molecular hydrogen ((Formula presented.)) generated via serpentinization to fuel subsurface microbial ecosystems independent from photosynthesis has prompted biogeochemical investigations of serpentinization-influenced fluids. However, investigations typically sample via surface seeps or open-borehole pumping, which can mix chemically distinct waters from different depths. Depth-indiscriminate sampling methods could thus hinder understanding of the spatial controls on nutrient availability for microbial life. To resolve distinct groundwaters in a low-temperature serpentinizing environment, we deployed packers (tools that seal against borehole walls during pumping) in two (Formula presented.) -deep, peridotite-hosted wells in the Samail Ophiolite, Oman. Isolation and pumping of discrete intervals as deep as (Formula presented.) to (Formula presented.) below ground level revealed multiple aquifers that ranged in pH from 8 to 11. Chemical analyses and 16S rRNA gene sequencing of deep, highly reacted (Formula presented.) groundwaters bearing up to (Formula presented.), (Formula presented.) methane ((Formula presented.)) and (Formula presented.) sulfate ((Formula presented.)) revealed an ecosystem dominated by Bacteria affiliated with the class Thermodesulfovibrionia, a group of chemolithoheterotrophs supported by (Formula presented.) oxidation coupled to (Formula presented.) reduction. In shallower, oxidized (Formula presented.) groundwaters, aerobic and denitrifying heterotrophs were relatively more abundant. High (Formula presented.) and (Formula presented.) of (Formula presented.) (up to (Formula presented.) and (Formula presented.), respectively) indicated microbial (Formula presented.) oxidation, particularly in (Formula presented.) waters with evidence of mixing with (Formula presented.) waters. This study demonstrates the power of spatially resolving groundwaters to probe their distinct geochemical conditions and chemosynthetic communities. Such information will help improve predictions of where microbial activity in fractured rock ecosystems might occur, including beyond Earth.</p

Data_Sheet_2_Parapatric speciation of Meiothermus in serpentinite-hosted aquifers in Oman.xlsx

The factors that control the distribution and evolution of microbial life in subsurface environments remain enigmatic due to challenges associated with sampling fluids from discrete depth intervals via boreholes while avoiding mixing of fluids. Here, using an inflatable packer system, fracture waters were isolated and collected from three discrete depth intervals spanning >130 m in a borehole intersecting an ultramafic rock formation undergoing serpentinization in the Samail Ophiolite, Sultanate of Oman. Near surface aquifer waters were moderately reducing and had alkaline pH while deeper aquifer waters were reduced and had hyperalkaline pH, indicating extensive influence by serpentinization. Metagenomic sequencing and analysis of DNA from filtered biomass collected from discrete depth intervals revealed an abundance of aerobes in near surface waters and a greater proportion of anaerobes at depth. Yet the abundance of the putatively obligate aerobe, Meiothermus, increased with depth, providing an opportunity to evaluate the influence of chemical and spatial variation on its distribution and speciation. Two clades of Meiothermus metagenome assembled genomes (MAGs) were identified that correspond to surface and deep populations termed Types I (S) and II (D), respectively; both clades comprised an apparently Oman-specific lineage indicating a common ancestor. Type II (D) clade MAGs encoded fewer genes and were undergoing slower genome replication as inferred from read mapping. Further, single nucleotide variants (SNVs) and mobile genetic elements identified among MAGs revealed detectable, albeit limited, evidence for gene flow/recombination between spatially segregated Type I (S) and Type II (D) populations. Together, these observations indicate that chemical variation generated by serpentinization, combined with physical barriers that reduce/limit dispersal and gene flow, allowed for the parapatric speciation of Meiothermus in the Samail Ophiolite or a geologic precursor. Further, Meiothermus genomic data suggest that deep and shallow aquifer fluids in the Samail Ophiolite may mix over shorter time scales than has been previously estimated from geochemical data.</p

Data_Sheet_1_Parapatric speciation of Meiothermus in serpentinite-hosted aquifers in Oman.DOCX

The factors that control the distribution and evolution of microbial life in subsurface environments remain enigmatic due to challenges associated with sampling fluids from discrete depth intervals via boreholes while avoiding mixing of fluids. Here, using an inflatable packer system, fracture waters were isolated and collected from three discrete depth intervals spanning >130 m in a borehole intersecting an ultramafic rock formation undergoing serpentinization in the Samail Ophiolite, Sultanate of Oman. Near surface aquifer waters were moderately reducing and had alkaline pH while deeper aquifer waters were reduced and had hyperalkaline pH, indicating extensive influence by serpentinization. Metagenomic sequencing and analysis of DNA from filtered biomass collected from discrete depth intervals revealed an abundance of aerobes in near surface waters and a greater proportion of anaerobes at depth. Yet the abundance of the putatively obligate aerobe, Meiothermus, increased with depth, providing an opportunity to evaluate the influence of chemical and spatial variation on its distribution and speciation. Two clades of Meiothermus metagenome assembled genomes (MAGs) were identified that correspond to surface and deep populations termed Types I (S) and II (D), respectively; both clades comprised an apparently Oman-specific lineage indicating a common ancestor. Type II (D) clade MAGs encoded fewer genes and were undergoing slower genome replication as inferred from read mapping. Further, single nucleotide variants (SNVs) and mobile genetic elements identified among MAGs revealed detectable, albeit limited, evidence for gene flow/recombination between spatially segregated Type I (S) and Type II (D) populations. Together, these observations indicate that chemical variation generated by serpentinization, combined with physical barriers that reduce/limit dispersal and gene flow, allowed for the parapatric speciation of Meiothermus in the Samail Ophiolite or a geologic precursor. Further, Meiothermus genomic data suggest that deep and shallow aquifer fluids in the Samail Ophiolite may mix over shorter time scales than has been previously estimated from geochemical data.</p