A new chemolithoautotrophic arsenite-oxidizing bacterium isolated from a gold mine: Phylogenetic, physiological, and preliminary biochemical studies

A previously unknown chemolithoautotrophic arsenite-oxidizing bacterium has been isolated from a gold mine in the Northern Territory of Australia. The organism, designated NT-26, was found to be a gram-negative motile rod wit h two subterminal flagella. In a minimal medium containing only arsenite as the electron donor (5 mM), oxygen as the electron acceptor, and carbon dio xide-bicarbonate as the carbon source, the doubling time for chemolithoauto trophic growth was 7.6 h. Arsenite oxidation was found to be catalyzed by a periplasmic arsenite oxidase (optimum pH, 5.5). Based upon 16S rDNA phylog enetic sequence analysis, NT-26 belongs to the Agrobacterium/Rhizbium branc h of the alpha-Proteobacteria and may represent a new species. This recentl y discovered organism is the most rapidly growing chemolithoautotrophic ars enite oxidizer known.