Numéro |
J. Phys. IV France
Volume 107, May 2003
|
|
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Page(s) | 49 - 52 | |
DOI | https://doi.org/10.1051/jp4:20030240 |
J. Phys. IV France 107 (2003) 49
DOI: 10.1051/jp4:20030240
Metabolic energy from arsenite oxidation in Alcaligenes faecalis
G.L. Anderson, M. Love and B.K. ZeiderDepartment of Chemistry, Indiana University South Bend, South Bend, IN 46634-7111, U.S.A.
Abstract
The aerobic soil bacterium, Alcaligenes faecalis, survives in cultures containing
greater than 10 g/L of aqueous arsenic. Toleration of arsenite occurs by the enzymatic oxidation
of arsenite (As
), to the less toxic arsenate (As
). In defined media, the bacterium grows faster
in the presence of arsenite than in its absence. This suggests that the bacterium uses the redox
potential of arsenite oxidation as metabolic energy. The oxidation occurs via periplasmic
arsenite oxidase, azurin, and cytochrome c [11] which presumably pass electron equivalents
through an electron transport chain involving cytochrome c oxidase aud oxygen as the terminal
electron acceptor. The associated proton translocation would allow synthesis of ATP and
provide a useful means of harnessing the redox potential of arsenite oxidation.
Arsenite and arsenate assays of the media during bacterial growth indicate that arsenite is
depleted during the exponential growth phase and occurs concomitantly with the expression of
arsenite oxidase. These results suggest that arsenite is detoxified to arsenate during bacterial
growth and are inconsistent with previous reported interpretations of growth data.
Alcaligenes faecalis is dependent on organic carbon sources and is therefore not
chemolithoautotrophic. The relationship between succinate and arsenite utilisation provides
evidence for the use of arsenite as a supplemental energy source.
Because Alcaligenes faecalis not only tolerates, but thrives, in very high concentrations of
arsenic has important implications in bioremediation of environments contaminated by aqueous
arsenic.
© EDP Sciences 2003