Craig Baker-Austin^1,6, Mark Dopson^1,2, Margaret Wexler¹, R. Gary Sawers³, Ann Stemmler⁴,
Barry P. Rosen⁴, and Philip L. Bond<sup>1,5,7


1</sup>School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
²Molecular Biology, Umeå University, SE-901 87 Umeå, Sweden
³Department of Molecular Biology, John Innes Centre, Norwich NR4 7UH, UK
⁴Department of Biochemistry and Molecular Biology, Wayne state University, School of Medicine, Detroit, MI 48210, USA
⁵Centre for Ecology, Evolution and Conservation, University of East Anglia, Norwich NR4 7TJ, UK
⁶Savannah River Ecology Laboratory, The University of Georgia, Aiken, SC 29802, USA
⁷Advanced Wastewater Management Centre, University of Queensland, Brisbane 4072 QLD, Australia

Abstract
‘Ferroplasma acidarmanus’ Fer1 is an arsenic-hypertolerant acidophilic archaeon isolated from the Iron Mountain mine, California; a site characterized by heavy metals contamination. The presence of up to 10 g arsenate per litre [As(V); 133 mM] did not significantly reduce growth yields, whereas between 5 and 10 g arsenite per litre [As(III); 67–133 mM] significantly reduced the yield. Previous bioinformatic analysis indicates that ‘F. acidarmanus’ Fer1 has only two predicted genes involved in arsenic resistance and lacks a recognizable gene for an arsenate reductase. Biochemical analysis suggests that ‘F. acidarmanus’ Fer1 does not reduce arsenate indicating that ‘F. acidarmanus’ Fer1 has an alternative resistance mechanism to arsenate other than reduction to arsenite and efflux. Primer extension analysis of the putative ars transcriptional regulator (arsR) and efflux pump (arsB) demonstrated that these genes are co-transcribed, and expressed in response to arsenite, but not arsenate. Two-dimensional polyacrylamide gel electrophoresis analysis of ‘F. acidarmanus’ Fer1 cells exposed to arsenite revealed enhanced expression of proteins associated with protein refolding, including the thermosome Group II HSP60 family chaperonin and
HSP70 DnaK type heat shock proteins. This report represents the first molecular and proteomic study of arsenic resistance in an acidophilic archaeon.



Keywords
Ferroplasma, Arsenic resistance, Arsenite, Proteomics, Primer extension



SREL Reprint #3036



Baker-Austin, C., M. Dopson, M. Wexler, R. G. Sawers, A. Stemmler, B. P. Rosen, and P. L. Bond. 2007. Extreme arsenic resistance by the acidophilic archaeon ‘Ferroplasma acidarmanus’ Fer1. Extremophiles (2007)11:425-434.

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