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Multiple sulfur isotope signatures of sulfite and thiosulfate reduction by the model dissimilatory sulfate-reducer, Desulfovibrio alaskensis str. G20

Leavitt, William D. and Cummins, Renata C. and Schmidt, Marian L. and Sim, Min S. and Ono, Shuhei and Bradley, Alexander S. and Johnston, David T. (2014) Multiple sulfur isotope signatures of sulfite and thiosulfate reduction by the model dissimilatory sulfate-reducer, Desulfovibrio alaskensis str. G20. Frontiers in Microbiology, 5 . Art. No. 591. ISSN 1664-302X. PMCID PMC4243691.

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Dissimilatory sulfate reduction serves as a key metabolic carbon remineralization process in anoxic marine environments. Sulfate reducing microorganisms can impart a wide range in mass-dependent sulfur isotopic fractionation. As such, the presence and relative activity of these organisms is identifiable from geological materials. By extension, sulfur isotope records are used to infer the redox balance of marine sedimentary environments, and the oxidation state of Earth's oceans and atmosphere. However, recent work suggests that our understanding of microbial sulfate reduction (MSRs) may be missing complexity associated with the presence and role of key chemical intermediates in the reductive process. This study provides a test of proposed metabolic models of sulfate reduction by growing an axenic culture of the well-studied MSRs, Desulfovibrio alaskensis strain G20, under electron donor limited conditions on the terminal electron acceptors sulfate, sulfite or thiosulfate, and tracking the multiple S isotopic consequences of each condition set. The dissimilatory reduction of thiosulfate and sulfite produce unique minor isotope effects, as compared to the reduction of sulfate. Further, these experiments reveal a complex biochemistry associated with sulfite reduction. That is, under high sulfite concentrations, sulfur is shuttled to an intermediate pool of thiosulfate. Site-specific isotope fractionation (within thiosulfate) is very large (34ε ~ 30‰) while terminal product sulfide carries only a small fractionation from the initial sulfite (34ε < 10‰): a signature similar in magnitude to sulfate and thiosulfate reduction. Together these findings show that microbial sulfate reduction (MSR) is highly sensitive to the concentration of environmentally important sulfur-cycle intermediates (sulfite and thiosulfate), especially when thiosulfate and the large site-specific isotope effects are involved.

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Additional Information:© 2014 Leavitt, Cummins, Schmidt, Sim, Ono, Bradley and Johnston. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 05 September 2014; Accepted: 20 October 2014; Published online: 25 November 2014. Renata Cummins thanks Harvard University EPS for sponsoring her thesis work, later extended into this manuscript. We thank Colleen Hansel for her generosity in sharing lab space and equipment. Thanks to Andy Masterson for analytical expertise and Erin Beirne for assistance with data generation. Funding provided by NASA-Exobiology (David T. Johnston and Alexander S. Bradley), NSF GRFP (William D. Leavitt), NSF CAREER, NSF Instrument and facilities (David T. Johnston), NSF Low Temperature Geochemistry (Shuhei Ono and Min S. Sim) awards.
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NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:microbial sulfate reduction; multiple sulfur isotopes; biogeochemical sulfur cycle; thionates; sulfur intermediates
PubMed Central ID:PMC4243691
Record Number:CaltechAUTHORS:20150112-104603696
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Official Citation:Leavitt WD, Cummins R, Schmidt ML, Sim MS, Ono S, Bradley AS and Johnston DT (2014) Multiple sulfur isotope signatures of sulfite and thiosulfate reduction by the model dissimilatory sulfate-reducer, Desulfovibrio alaskensis str. G20. Front. Microbiol. 5:591. doi: 10.3389/fmicb.2014.00591
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53562
Deposited By: Jason Perez
Deposited On:13 Jan 2015 22:40
Last Modified:03 Oct 2019 07:50

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