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Science 17 April 2009:
Vol. 324. no. 5925, pp. 397 - 400
DOI: 10.1126/science.1167350
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Reports

A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"

Jill A. Mikucki,1* Ann Pearson,1 David T. Johnston,2 Alexandra V. Turchyn,3 James Farquhar,4 Daniel P. Schrag,1 Ariel D. Anbar,5 John C. Priscu,6 Peter A. Lee7

An active microbial assemblage cycles sulfur in a sulfate-rich, ancient marine brine beneath Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet, with Fe(III) serving as the terminal electron acceptor. Isotopic measurements of sulfate, water, carbonate, and ferrous iron and functional gene analyses of adenosine 5'-phosphosulfate reductase imply that a microbial consortium facilitates a catalytic sulfur cycle. These metabolic pathways result from a limited organic carbon supply because of the absence of contemporary photosynthesis, yielding a subglacial ferrous brine that is anoxic but not sulfidic. Coupled biogeochemical processes below the glacier enable subglacial microbes to grow in extended isolation, demonstrating how analogous organic-starved systems, such as Neoproterozoic oceans, accumulated Fe(II) despite the presence of an active sulfur cycle.

1 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138 USA.
2 Department of Organismic and Evolutionary Biology, Harvard University, Cambridge MA, 02138 USA.
3 Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.
4 Department of Geology, University of Maryland, College Park, MD 20742, USA.
5 School of Earth and Space Exploration and Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
6 Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT 59717, USA.
7 Hollings Marine Laboratory, College of Charleston, Charleston, SC 29412, USA.

* Present address: Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA. To whom correspondence should be addressed. E-mail: jill.a.mikucki{at}dartmouth.edu

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