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Science 14 September 2007:
Vol. 317. no. 5844, pp. 1534 - 1537
DOI: 10.1126/science.1145861
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Reports

Early Archaean Microorganisms Preferred Elemental Sulfur, Not Sulfate

Pascal Philippot,1* Mark Van Zuilen,1 Kevin Lepot,1 Christophe Thomazo,1 James Farquhar,2 Martin J. Van Kranendonk3

Microscopic sulfides with low 34S/32S ratios in marine sulfate deposits from the 3490-million-yearold Dresser Formation, Australia, have been interpreted as evidence for the presence of early sulfate-reducing organisms on Earth. We show that these microscopic sulfides have a mass-independently fractionated sulfur isotopic anomaly ({Delta}33S) that differs from that of their host sulfate (barite). These microscopic sulfides could not have been produced by sulfate-reducing microbes, nor by abiologic processes that involve reduction of sulfate. Instead, we interpret the combined negative {delta}34S and positive {Delta}33S signature of these microscopic sulfides as evidence for the early existence of organisms that disproportionate elemental sulfur.

1 Equipe Géobiosphère Actuelle et Primitive, Institut de Physique du Globe de Paris, CNRS and Université Denis Diderot, 4 place Jussieu, 75005 Paris cedex, France.
2 Earth System Science Interdisciplinary Center, Department of Geology, University of Maryland, College Park, MD 20742, USA.
3 Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, Australia.

* To whom correspondence should be addressed. E-mail: philippot{at}ipgp.jussieu.fr

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Comment on "Early Archaean Microorganisms Preferred Elemental Sulfur, Not Sulfate".
H. Bao, T. Sun, I. Kohl, and Y. Peng (2008)
Science 319, 1336b
   Abstract »    Full Text »    PDF »
Response to Comment on "Early Archaean Microorganisms Preferred Elemental Sulfur, Not Sulfate".
P. Philippot, M. Van Zuilen, K. Lepot, C. Thomazo, J. Farquhar, and M. J. Van Kranendonk (2008)
Science 319, 1336c
   Abstract »    Full Text »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)