Combined 34 S, 33 S and 18 O isotope fractionations record different intracellular steps of microbial sulfate reduction

Antler, Gilad and Turchyn, Alexandra V. and Ono, Shuhei and Sivan, Orit and Bosak, Tanja (2017) Combined 34 S, 33 S and 18 O isotope fractionations record different intracellular steps of microbial sulfate reduction. Geochimica Et Cosmochimica Acta, 203. pp. 364-380. ISSN 0016-7037 DOI https://doi.org/10.1016/j.gca.2017.01.015

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Abstract

Several enzymatic steps in microbial sulfate reduction (MSR) fractionate the isotope ratios of 33S/32S, 34S/32S and 18O/16O in extracellular sulfate, but the effects of different intracellular processes on the isotopic composition of residual sulfate are still not well quantified. We measured combined multiple sulfur (33S/32S, 34S/32S) and oxygen (18O/16O) isotope ratios of sulfate in pure cultures of a marine sulfate reducing bacterium Desulfovibrio sp. DMSS-1 grown on different organic substrates. These measurements are consistent with the previously reported correlations of oxygen and sulfur isotope fractionations with the cell-specific rate of MSR: faster reduction rates produced smaller isotopic fractionations for all isotopes. Combined isotope fractionation of oxygen and multiple sulfur isotopes are also consistent with the relationship between the rate limiting step during microbial sulfate reduction and the availability of the DsrC subunit. These experiments help reconstruct and interpret processes that operate in natural pore waters characterized by high 18O/16O and moderate 34S/32S ratios and suggest that some multiple isotope signals in the environment cannot be explained by microbial sulfate reduction alone. Instead, these signals support the presence of active, but slow sulfate reduction as well as the reoxidation of sulfide.

Item Type:	Article
Uncontrolled Keywords:	2017AREP; IA72;
Subjects:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions:	01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title:	Geochimica Et Cosmochimica Acta
Volume:	203
Page Range:	pp. 364-380
Identification Number:	https://doi.org/10.1016/j.gca.2017.01.015
Depositing User:	Sarah Humbert
Date Deposited:	04 Aug 2017 11:04
Last Modified:	04 Aug 2017 11:04
URI:	http://eprints.esc.cam.ac.uk/id/eprint/4004

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