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Molecular evidence for an active microbial methane cycle in subsurface serpentinite-hosted groundwaters in the Samail Ophiolite, Oman

Molecular evidence for an active microbial methane cycle in subsurface serpentinite-hosted groundwaters in the Samail Ophiolite, Oman
Molecular evidence for an active microbial methane cycle in subsurface serpentinite-hosted groundwaters in the Samail Ophiolite, Oman
Serpentinization can generate highly reduced fluids replete with hydrogen (H2) and methane (CH4), potent reductants capable of driving microbial methanogenesis and methanotrophy, respectively. However, CH4 in serpentinized waters is thought to be primarily abiogenic, raising key questions about the relative importance of methanogens and methanotrophs in the production and consumption of CH4 in these systems. Herein, we apply molecular approaches to examine the functional capability and activity of microbial CH4 cycling in serpentinization-impacted subsurface waters intersecting multiple rock and water types within the Samail Ophiolite of Oman. Abundant 16S rRNA genes and transcripts affiliated with the methanogenic genus Methanobacterium were recovered from the most alkaline (pH, >10), H2- and CH4-rich subsurface waters. Additionally, 16S rRNA genes and transcripts associated with the aerobic methanotrophic genus Methylococcus were detected in wells that spanned varied fluid geochemistry. Metagenomic sequencing yielded genes encoding homologs of proteins involved in the hydrogenotrophic pathway of microbial CH4 production and in microbial CH4 oxidation. Transcripts of several key genes encoding methanogenesis/methanotrophy enzymes were identified, predominantly in communities from the most hyperalkaline waters. These results indicate active methanogenic and methanotrophic populations in waters with hyperalkaline pH in the Samail Ophiolite, thereby supporting a role for biological CH4 cycling in aquifers that undergo low-temperature serpentinization.
Ophiolite, environmental microbiology, geomicrobiology, methane, methanogens, serpentinization
0099-2240
1-18
Kraus, Emily A.
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Nothaft, Daniel
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Stamps, Blake W.
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Rempfert, Kaitlin R.
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Ellison, Eric T.
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Matter, Juerg M.
abb60c24-b6cb-4d1a-a108-6fc51ee20395
Templeton, Alexis S.
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Boyd, Eric S.
049410ba-5542-4cd7-868e-10e58702d46a
Spear, John R.
b8d4e732-7335-40b9-b5bb-21443aa3a045
Kraus, Emily A.
cae3050d-5ce0-4232-b192-b97e2f91525e
Nothaft, Daniel
f0654729-4128-466d-8b44-f74279ede779
Stamps, Blake W.
89920a81-28b5-4cfe-bb33-618f77371365
Rempfert, Kaitlin R.
f9684cb0-b63d-4bca-b47b-e049a2aad131
Ellison, Eric T.
7feb77ff-0ede-4bce-9a7f-0ca7c5a0384f
Matter, Juerg M.
abb60c24-b6cb-4d1a-a108-6fc51ee20395
Templeton, Alexis S.
f65afca4-9076-4bdb-8214-91bbd6c775b0
Boyd, Eric S.
049410ba-5542-4cd7-868e-10e58702d46a
Spear, John R.
b8d4e732-7335-40b9-b5bb-21443aa3a045

Kraus, Emily A., Nothaft, Daniel, Stamps, Blake W., Rempfert, Kaitlin R., Ellison, Eric T., Matter, Juerg M., Templeton, Alexis S., Boyd, Eric S. and Spear, John R. (2021) Molecular evidence for an active microbial methane cycle in subsurface serpentinite-hosted groundwaters in the Samail Ophiolite, Oman. Applied and Environmental Microbiology, 87 (2), 1-18, [e02068-20]. (doi:10.1128/AEM.02068-20).

Record type: Article

Abstract

Serpentinization can generate highly reduced fluids replete with hydrogen (H2) and methane (CH4), potent reductants capable of driving microbial methanogenesis and methanotrophy, respectively. However, CH4 in serpentinized waters is thought to be primarily abiogenic, raising key questions about the relative importance of methanogens and methanotrophs in the production and consumption of CH4 in these systems. Herein, we apply molecular approaches to examine the functional capability and activity of microbial CH4 cycling in serpentinization-impacted subsurface waters intersecting multiple rock and water types within the Samail Ophiolite of Oman. Abundant 16S rRNA genes and transcripts affiliated with the methanogenic genus Methanobacterium were recovered from the most alkaline (pH, >10), H2- and CH4-rich subsurface waters. Additionally, 16S rRNA genes and transcripts associated with the aerobic methanotrophic genus Methylococcus were detected in wells that spanned varied fluid geochemistry. Metagenomic sequencing yielded genes encoding homologs of proteins involved in the hydrogenotrophic pathway of microbial CH4 production and in microbial CH4 oxidation. Transcripts of several key genes encoding methanogenesis/methanotrophy enzymes were identified, predominantly in communities from the most hyperalkaline waters. These results indicate active methanogenic and methanotrophic populations in waters with hyperalkaline pH in the Samail Ophiolite, thereby supporting a role for biological CH4 cycling in aquifers that undergo low-temperature serpentinization.

Text
Applied and Environmental Microbiology-2020-Kraus-AEM.02068-20.full - Accepted Manuscript
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Accepted/In Press date: 20 October 2020
e-pub ahead of print date: 4 January 2021
Published date: January 2021
Keywords: Ophiolite, environmental microbiology, geomicrobiology, methane, methanogens, serpentinization

Identifiers

Local EPrints ID: 446652
URI: http://eprints.soton.ac.uk/id/eprint/446652
ISSN: 0099-2240
PURE UUID: 61f84e54-1b97-4088-9999-c2fdcb6e62e5
ORCID for Juerg M. Matter: ORCID iD orcid.org/0000-0002-1070-7371

Catalogue record

Date deposited: 17 Feb 2021 17:31
Last modified: 22 Nov 2021 08:18

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Contributors

Author: Emily A. Kraus
Author: Daniel Nothaft
Author: Blake W. Stamps
Author: Kaitlin R. Rempfert
Author: Eric T. Ellison
Author: Juerg M. Matter ORCID iD
Author: Alexis S. Templeton
Author: Eric S. Boyd
Author: John R. Spear

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