Transformation of inorganic and organic arsenic by Alkaliphilus oremlandii sp. nov. strain OhILAs

Abstract

Alkaliphilus oremlandii sp. nov. strain OhILAs is a mesophilic, spore-forming, motile, low mole%GC gram positive. It was enriched from Ohio River sediments on a basal medium with 20 mM lactate and 5 mM arsenate and isolated through passage on medium with increased arsenic concentration (10 and 20 mM), tindalization, and serial dilution. The pH optimal for growth was 8.4 and 16S rRNA gene sequence analysis indicated it is most closely related to species in the genus Alkaliphilus (A. crotonoxidans 95%, A. auruminator 95%, A. metalliredigens, 94%). A strict anaerobe, it can ferment lactate via the acrylate pathway as well as fructose and glycerol. A. oremlandii also has respiratory capability, as it is able to use arsenate and thiosulfate as terminal electron acceptors with acetate, pyruvate, formate, lactate, fumarate, glycerol, or fructose as the electron donor. A respiratory arsenate reductase, which is constitutively expressed, has been identified through biochemical and Western blot analyses and confirmed by cloning and sequencing of the gene encoding the structural subunit arrA. The entire arr operon as well as the ars operon have also been identified in the fully annotated genome. A. oremlandii also transforms the organoarsenical 3-nitro-4-hydroxy benzene arsonic acid (roxarsone). Growth experiments and genomic analysis suggest that it couples the reduction of the nitro group of the organoarsenical to the oxidation of either lactate or fructose in a dissimilatory manner, generating ATP via a sodium dependent ATP synthase. © 2008 New York Academy of Sciences.