Resistance to arsenic compounds in microorganisms

Authors

  • Carlos Cervantes,

    Corresponding author
    1. Instituto de Ineestigaeiones Quimico-Biológicas, Unirersidad Michoacana, 58240 Morelia, Mich., Mexico
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  • Guangyong Ji,

    1. Department of Microbiology and Immunology (M/C 790), ROOM E-703 MSB, University of Illinois College of Medicine, 835 South Wolcott Auenue, Chicago, IL 60612-7344, USA
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    • 1

      Skirball Institute, New York University Medical Center, New York, NY 10016 USA.

  • JoséLuis Ramirez,

    1. Facultad de Medicina, Unirersidad Autónoma de San Luis Potosí, San Luis Potosí, SLP, Mexico
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  • Simon Silver

    1. Department of Microbiology and Immunology (M/C 790), ROOM E-703 MSB, University of Illinois College of Medicine, 835 South Wolcott Auenue, Chicago, IL 60612-7344, USA
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*Corresponding authors. Tel.: (312) 996 9608; Fax: (312) 996 6415; and Tel.: (+5243) 14 2152; Fax (312) 16 7436; E-mail: U20053@JCVM.UIC.EDU

Abstract

Abstract: Arsenic ions, frequently present as environmental pollutants, are very toxic for most microorganisms. Some microbial strains possess genetic determinants that confer resistance. In bacteria, these determinants are often found on plasmids, which has facilitated their study at the molecular level. Bacterial plasmids conferring arsenic resistance encode specific efflux pumps able to extrude arsenic from the cell cytoplasm thus lowering the intracellular concentration of the toxic ions. In Gram-negative bacteria, the efflux pump consists of a two-component ATPase complex. ArsA is the ATPase subunit and is associated with an integral membrane subunit, ArsB. Arsenate is enzymatically reduced to arsenite (the substrate of ArsB and the activator of ArsA) by the small cytoplasmic ArsC polypeptide. In Gram-positive bacteria, comparable arsB and arsC genes (and proteins) are found, but arsA is missing. In addition to the wide spread plasmid arsenic resistance determinant, a few bacteria confer resistance to arsenite with a separate determinant for enzymatic oxidation of more-toxic arsenite to less-toxic arsenate. In contrast to the detailed information on the mechanisms of arsenic resistance in bacteria, little work has been reported on this subject in algae and fungi.

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