Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction
- PDF / 194,931 Bytes
- 9 Pages / 595 x 785 pts Page_size
- 41 Downloads / 163 Views
© Springer-Verlag 2000
O R I G I N A L PA P E R
Joan M. Macy · Joanne M. Santini · Björg V. Pauling · Andrew H. O’Neill · Lindsay I. Sly
Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction
Received: 18 March 1999 / Accepted: 27 September 1999
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 membranebound 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
J. M. Macy (Y) · J. M. Santini · B. V. Pauling Department of Microbiology, La Trobe University, Bundoora, Victoria 3083, Australia e-mail: [email protected], Tel.: +61-3-94792229, Fax: +61-3-94791222 A. H. O’Neill · L. I. Sly Centre for Bacterial Diversity and Identification, Department of Microbiology and Parasitology, The University of Queensland, Brisbane, Queensland 4072, Australia
Introduction A number of bacteria have been isolated that use arsenate as the terminal electron acceptor. Four of these organisms (“Geospirillum arsenophilus”, formerly strain MIT-13; “Geospirillum barnseii”, formerly strain SES-3; a sulfatereducing bacterium “Desulfotomaculum auripigmentum”; and “Bacillus arsenicoselenatis”) grow using lactate, but not acetate, as the electron donor (Newman et al. 1997b; Blum et al. 1998). The only arsenate reducer that is able to grow using acetate as the electron donor is Chrysiogenes arsenatis (Macy et al. 1996), and arsenate reduction is catalyzed by a terminal arsenate reductase, Arr (Krafft and Macy 1998). Recently purified, this enzyme was found to be a heterodimeric (α1β1) molybdoenzyme that is located in the periplasmic space of the organism (Krafft and Macy 1998). Arsenate reduction by this organism is thought to be the terminal step of an electron transport system involved in energy con
Data Loading...
