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Published January 2002 | public
Journal Article

Oxidation of Arsenite by Agrobacterium albertimagni, AOL15, sp. nov., Isolated from Hot Creek, California


An arsenite-oxidizing bacterium, Agrobacterium albertimagni strain AOL15 (ATCC BAA-24), was isolated from the surface of aquatic macrophytes collected in Hot Creek, California. Under laboratory conditions, whole cell suspensions of AOL15 oxidized arsenite with a K_s of 3.4 ± 2.2µM and a V_(Max) of 1.81 ± 0.58 x 10^(-12) µmole · cell^(-1)· min^(-1) (or 0.043 ± 0.017 µmole · mg protein^(-1)· min^(-1)). The K_s value for AOL15 is the lowest value to date reported for whole cell suspensions and is comparable to ambient concentrations of arsenic of 2.7 µM reported for Hot Creek, indicating that AOL15 can oxidize arsenite under ambient conditions. Previous studies at this site revealed a rapid in situ oxidation of geothermally-derived arsenite while field incubation studies demonstrated that this oxidation was bacterially mediated. The isolation of the arsenite oxidizer AOL15 from this environment supports these previous observations. Arsenite does not support chemolithoautotrophic growth of AOL15 and toxicity studies with AOL15 showed that arsenite (at 5 mM) is toxic to AOL15, yet arsenate concentrations as high as 50 mM do not show any toxic effects. These results suggest that the oxidation of arsenite by AOL15 is a detoxification mechanism.

Additional Information

© 2002 Taylor & Francis. Received 22 March 2001; accepted 3 July 2001. Published online: 10 Nov 2010. The authors would like to acknowledge Dr. Steve Lindow (University of California Davis) for the identification of the macrophytes , Dr. Brian Lanoil (Caltech) for assistance with the phylogenetic analysis, Bridget L.West (Caltech) for assistance with the kinetics experiments, and Prof. Jared Leadbetter (Caltech) for helpful discussion. This work was funded in part by the National Science Foundation (EAR-9807662).

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