Original paper

Archives of Microbiology

, Volume 173, Issue 1, pp 49-57

First online:

Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction

  • J. M. MacyAffiliated withDepartment of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia e-mail: j.macy@latrobe.edu.au, Tel.: +61-3-94792229, Fax: +61-3-94791222
  • , J. M. SantiniAffiliated withDepartment of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia e-mail: j.macy@latrobe.edu.au, Tel.: +61-3-94792229, Fax: +61-3-94791222
  • , B. V. PaulingAffiliated withDepartment of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia e-mail: j.macy@latrobe.edu.au, Tel.: +61-3-94792229, Fax: +61-3-94791222
  • , A. H. O’NeillAffiliated withCentre for Bacterial Diversity and Identification, Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland 4072, Australia
  • , L. I. SlyAffiliated withCentre for Bacterial Diversity and Identification, Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland 4072, Australia

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Abstract

Two sulfate-reducing bacteria, which also reduce arsenate, were isolated; both organisms oxidized lactate incompletely to acetate. When using lactate as the electron donor, one of these organisms, Desulfomicrobium strain Ben-RB, rapidly reduced (doubling time = 8 h) 5.1 mM arsenate at the same time it reduced sulfate (9.6 mM). Sulfate reduction was not inhibited by the presence of arsenate. Arsenate could act as the terminal electron acceptor in minimal medium (doubling time = 9 h) in the absence of sulfate. Arsenate was reduced by a membrane-bound enzyme that is either a c-type cytochrome or is associated with such a cytochrome; benzyl-viologen-dependent arsenate reductase activity was greater in cells grown with arsenate/sulfate than in cells grown with sulfate only. The second organism, Desulfovibrio strain Ben-RA, also grew (doubling time = 8 h) while reducing arsenate (3.1 mM) and sulfate (8.3 mM) concomitantly. No evidence was found, however, that this organism is able to grow using arsenate as the terminal electron acceptor. Instead, it appears that arsenate reduction by the Desulfovibrio strain Ben-RA is catalyzed by an arsenate reductase that is encoded by a chromosomally-borne gene shown to be homologous to the arsC gene of the Escherichia coli plasmid, R773 ars system.

Key words Arsenate reduction Sulfate reduction Desulfovibrio sp. Desulfomicrobium sp. Arsenate ¶reductase Cytochrome c Arsenate resistance