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Abstract
Stable sulphur isotope fractionation was investigated during reduction of thiosulphate and elemental sulphur at 28°C by growing batch cultures of the sulphur- and thiosulphate-reducing bacteria Dethiosulfovibrio marinus (type strain DSM 12537) and Dethiosulfovibrio russensis (type strain DSM 12538), using citrate as carbon and energy source. The cell-specific thiosulphate reduction rate in the growth phase was 7.4±3.9 fmol cell−1 d−1. The hydrogen sulphide produced was enriched in 32S by 10.3±1 ‰ compared with total thiosulphate sulphur, close to previous experimental results observed for other sulphate- and non-sulphate-reducing bacteria. Elemental sulphur reduction yields sulphur isotope enrichment factors between−1.3 and−5.2 ‰ for D. russensis and−1.7 and−5.1 ‰ for D. marinus. The smaller fractionation effects are observed in the exponential growth phase (cellular rates between 5 and 70 fmol S° cell−1 d−1) and enhanced discrimination under conditions of citrate depletion and cell lysis (cellular rates between 0.3 and 3 fmol S° cell−1 d−1).
Acknowledgements
We thank G.A. Dubinina for providing the strains used in the present study. M.E.B. thanks S. Lilienthal for laboratory assistance and J. Rullkötter for giving access to analytical facilities at the ICBM, University of Oldenburg. We dedicate this publication to Heimo Nielsen on the occasion of his 90th birthday. The study was supported by Max Planck Society, Munich, and Leibniz IOW, Warnemünde. Furthermore, musical inspiration during manuscript preparation by P. Cole, P. Gabriel, A. Humpe, P. Simon, and B. Thomson is gratefully acknowledged. Thanks are also due to H. Cypionka, S. Sievert, and B. Jørgensen for stimulating discussions.