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Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps

Sivan, Orit and Antler, Gilad and Turchyn, Alexandra V. and Marlow, Jeffrey J. and Orphan, Victoria J. (2014) Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps. Proceedings of the National Academy of Sciences of the United States of America, 111 (40). E4139-E4147. ISSN 0027-8424. PMCID PMC4209987.

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Seep sediments are dominated by intensive microbial sulfate reduction coupled to the anaerobic oxidation of methane (AOM). Through geochemical measurements of incubation experiments with methane seep sediments collected from Hydrate Ridge, we provide insight into the role of iron oxides in sulfate-driven AOM. Seep sediments incubated with ^(13)C-labeled methane showed co-occurring sulfate reduction, AOM, and methanogenesis. The isotope fractionation factors for sulfur and oxygen isotopes in sulfate were about 40‰ and 22‰, respectively, reinforcing the difference between microbial sulfate reduction in methane seeps versus other sedimentary environments (for example, sulfur isotope fractionation above 60‰ in sulfate reduction coupled to organic carbon oxidation or in diffusive sedimentary sulfate–methane transition zone). The addition of hematite to these microcosm experiments resulted in significant microbial iron reduction as well as enhancing sulfate-driven AOM. The magnitude of the isotope fractionation of sulfur and oxygen isotopes in sulfate from these incubations was lowered by about 50%, indicating the involvement of iron oxides during sulfate reduction in methane seeps. The similar relative change between the oxygen versus sulfur isotopes of sulfate in all experiments (with and without hematite addition) suggests that oxidized forms of iron, naturally present in the sediment incubations, were involved in sulfate reduction, with hematite addition increasing the sulfate recycling or the activity of sulfur-cycling microorganisms by about 40%. These results highlight a role for natural iron oxides during bacterial sulfate reduction in methane seeps not only as nutrient but also as stimulator of sulfur recycling.

Item Type:Article
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URLURL TypeDescription DOIArticle Information CentralArticle
Turchyn, Alexandra V.0000-0002-9298-2173
Orphan, Victoria J.0000-0002-5374-6178
Additional Information:Copyright © 2014 National Academy of Sciences. Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved August 28, 2014 (received for review June 30, 2014) Published online before print September 22, 2014, doi: 10.1073/pnas.1412269111. We thank Stephanie Connon for the help in the laboratory, George Rossman for the hematite powder, and Jiwchar Ganor and his laboratory members for the help with the sulfate measurements. Thanks to Matthias Kellermann and Itay Bar-Or for the help and fruitful discussions. This research was supported by Israel Science Foundation Grant 643/12 (to O.S.), Department of Energy Biological Environmental Research Grant DE-SC0004949, and Gordon and Betty Moore Foundation Marine Microbiology Initiative Grant 3306 (to V.J.O.). Funding for sample collection was provided by National Science Foundation Biological Oceanography Grant 0825791. Author contributions: O.S. and V.J.O. designed research; O.S., G.A., and J.J.M. performed research; O.S., G.A., A.V.T., J.J.M., and V.J.O. analyzed data; and O.S., G.A., A.V.T., J.J.M., and V.J.O. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. This article contains supporting information online at
Funding AgencyGrant Number
Israel Science Foundation643/12
Department of Energy (DOE)DE-SC0004949
Gordon and Betty Moore Foundation3306
Subject Keywords:redox; anaerobic respiration; deep-sea; methanotrophy; ANME archaea
Issue or Number:40
PubMed Central ID:PMC4209987
Record Number:CaltechAUTHORS:20140923-111251974
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Official Citation:Orit Sivan, Gilad Antler, Alexandra V. Turchyn, Jeffrey J. Marlow, and Victoria J. Orphan Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps PNAS 2014 111 (40) E4139-E4147; published ahead of print September 22, 2014, doi:10.1073/pnas.1412269111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49939
Deposited By: George Porter
Deposited On:23 Sep 2014 20:33
Last Modified:09 Mar 2020 13:19

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