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Applied and Environmental Microbiology, February 2007, p. 1041-1048, Vol. 73, No. 4
0099-2240/07/$08.00+0     doi:10.1128/AEM.01654-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Molecular Analysis of Arsenate-Reducing Bacteria within Cambodian Sediments following Amendment with Acetate ^,

G. Lear,^1, B. Song,² A. G. Gault,¹ D. A. Polya,¹ and J. R. Lloyd^1*

Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, United Kingdom,¹ Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, North Carolina 28409²

Received 17 July 2006/ Accepted 3 November 2006

The health of millions is threatened by the use of groundwater contaminated with sediment-derived arsenic for drinking water and irrigation purposes in Southeast Asia. The microbial reduction of sorbed As(V) to the potentially more mobile As(III) has been implicated in release of arsenic into groundwater, but to date there have been few studies of the microorganisms that can mediate this transformation in aquifers. With the use of stable isotope probing of nucleic acids, we present evidence that the introduction of a proxy for organic matter (¹³C-labeled acetate) stimulated As(V) reduction in sediments collected from a Cambodian aquifer that hosts arsenic-rich groundwater. This was accompanied by an increase in the proportion of prokaryotes closely related to the dissimilatory As(V)-reducing bacteria Sulfurospirillum strain NP-4 and Desulfotomaculum auripigmentum. As(V) respiratory reductase genes (arrA) closely associated with those found in Sulfurospirillum barnesii and Geobacter uraniumreducens were also detected in active bacterial communities utilizing ¹³C-labeled acetate in microcosms. This study suggests a direct link between inputs of organic matter and the increased prevalence and activity of organisms which transform As(V) to the potentially more mobile and thus hazardous As(III) via dissimilatory As(V) reduction.

Published ahead of print on 17 November 2006.

Supplemental material for this article may be found at http://aem.asm.org/.

Present address: School of Biological Sciences, The University of Auckland, Private Bag 92-019, Auckland, New Zealand.