Biotransformation of arsenic by a Yellowstone thermoacidophilic eukaryotic alga

Proceedings of the National Academy of Sciences of the United States of America - Tập 106 Số 13 - Trang 5213-5217 - 2009
Jie Qin1, Corinne R. Lehr2, Chun‐Gang Yuan3,4,5, X. Chris Le3,4, Timothy R. McDermott2, Barry P. Rosen6
1Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI 48201 USA
2Department of Land Resources and Environmental Sciences and Thermal Biology Institute, Montana State University, Bozeman, MT 59717;
3Analytical and Environmental Toxicology,
4Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada T6G 2G3; and
5School of Environmental Science and Engineering, North China Electric Power University, Baoding 071003, Hebei Province, People's Republic of China
6Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, MI 48201

Tóm tắt

Arsenic is the most common toxic substance in the environment, ranking first on the Superfund list of hazardous substances. It is introduced primarily from geochemical sources and is acted on biologically, creating an arsenic biogeocycle. Geothermal environments are known for their elevated arsenic content and thus provide an excellent setting in which to study microbial redox transformations of arsenic. To date, most studies of microbial communities in geothermal environments have focused on Bacteria and Archaea , with little attention to eukaryotic microorganisms. Here, we show the potential of an extremophilic eukaryotic alga of the order Cyanidiales to influence arsenic cycling at elevated temperatures. Cyanidioschyzon sp. isolate 5508 oxidized arsenite [As(III)] to arsenate [As(V)], reduced As(V) to As(III), and methylated As(III) to form trimethylarsine oxide (TMAO) and dimethylarsenate [DMAs(V)]. Two arsenic methyltransferase genes, CmarsM7 and CmarsM8 , were cloned from this organism and demonstrated to confer resistance to As(III) in an arsenite hypersensitive strain of Escherichia coli . The 2 recombinant CmArsMs were purified and shown to transform As(III) into monomethylarsenite, DMAs(V), TMAO, and trimethylarsine gas, with a T opt of 60–70 °C. These studies illustrate the importance of eukaryotic microorganisms to the biogeochemical cycling of arsenic in geothermal systems, offer a molecular explanation for how these algae tolerate arsenic in their environment, and provide the characterization of algal methyltransferases.

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Proceedings of the National Academy of Sciences of the United States of America

Tập 106 Số 13

5213-5217

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