Redox cycling of arsenic by the hydrothermal marine bacteriumMarinobacter santoriniensis

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SummaryMarinobacter santoriniensisNKSG1T is a mesophilic, dissimilatory arsenate-reducing and arsenite-oxidizing bacterium isolated from an arsenate-reducing enrichment culture. The inoculum was obtained from arsenic-rich shallow marine hydrothermal sediment from Santorini, Greece, with evidence of arsenic redox cycling. Growth studies demonstratedM. santoriniensisNKSG1T is capable of conserving energy from the reduction of arsenate [As(V)] with acetate or lactate as the electron donor, and of oxidizing arsenite [As(III)] heterotrophically with oxygen as the electron acceptor. The oxidation of As(III) coincided with the expression of theaoxBgene encoding for the catalytic molybdopterin subunit of the heterodimeric arsenite oxidase operon, indicating the reaction is enzymatically controlled, andM. santoriniensisNKSG1T is a heterotrophic As(III)-oxidizing bacterium. Although it is clear that this organism also performs dissimilatory As(V) reduction, no amplification of thearrAarsenate reductase gene was attained using a range of primers and PCR conditions.Marinobacter santoriniensisNKSG1T belongs to a genus of bacteria widely occurring in marine environments, including hydrothermal sediments, and is among the first marine bacteria shown to be capable of either anaerobic As(V) respiration or aerobic As(III) oxidation.

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