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Vol. 71, No. 12, 2005; Pages: 8642–8648

Interactions between the Fe(III)-Reducing Bacterium
Geobacter sulfurreducens and Arsenate, and Capture
of the Metalloid by Biogenic Fe(II)

F. S. Islam,1 R. L. Pederick,1 A. G. Gault,1 L. K. Adams,1 D. A. Polya,1 J. M. Charnock,2 and J. R. Lloyd1*

School of Earth, Atmospheric and Environmental Sciences & Williamson Research Centre
for Molecular Environmental Science, University of Manchester, Manchester M13 9PL, United Kingdom.


Previous work has shown that microbial communities in As-mobilizing sediments from West Bengal were dominated by Geobacter species. Thus, the potential of Geobacter sulfurreducens to mobilize arsenic via direct enzymatic reduction and indirect mechanisms linked to Fe(III) reduction was analyzed. G. sulfurreducens was unable to conserve energy for growth via the dissimilatory reduction of As(V), although it was able to grow in medium containing fumarate as the terminal electron acceptor in the presence of 500 M As(V). There was also no evidence of As(III) in culture supernatants, suggesting that resistance to 500 M As(V) was not mediated by a classical arsenic resistance operon, which would rely on the intracellular reduction of As(V) and the efflux of As(III). When the cells were grown using soluble Fe(III) as an electron acceptor in the presence of As(V), the Fe(II)-bearing mineral vivianite was formed. This was accompanied by the removal of As, predominantly as As(V), from solution. Biogenic siderite (ferrous carbonate) was also able to remove As from solution. When the organism was grown using insoluble ferrihydrite as an electron acceptor, Fe(III) reduction resulted in the formation of magnetite, again accompanied by the nearly quantitative sorption of As(V). These results demonstrate that G. sulfurreducens, a model Fe(III)-reducing bacterium, did not reduce As(V) enzymatically, despite the apparent genetic potential to mediate this transformation. However, the reduction of Fe(III) led to the formation of Fe(II)-bearing phases that are able to capture arsenic species and could act as sinks for arsenic in sediments.

Keywords:Geobacter species;Geobacter sulfurreducens;Fe(III) reduction;Biogenic siderite;ferrous carbonate;Geobacteraceae;ferrihydrite;radionuclides.

Corresponding author: Tel 0161-275-7155; Fax 0161-275-3947

E-mail: jon.lloyd@manchester.ac.uk


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