Isolation of arsenite-oxidizing bacteria from a natural biofilm associated to volcanic rocks of Atacama Desert, Chile.

Arsenic is naturally present in rocks, soil, water, and air. It is released to the environment by natural processes such as volcanic eruptions, and rock erosion. In this study, two arsenite-oxidizing strains were isolated from volcanic rocks obtained from the Camarones Valley, Atacama Desert, Chile. Strains were isolated from biofilms and identified by 16s ARNr sequences analysis. aox genes were detected by RT-PCR. The arsenic oxidation ability was assayed with silver nitrate and HPLC-HG-AAS. Four arsenite-resistant strains were isolated (8 mM). RT-PCR analysis showed the presence of aox genes in UC-2 and UC-6 strains. In addition, UC-2 and UC-6 strains were able to oxidize 90 and 95% arsenite present in the medium to arsenate, at a rate of 9.3 and 9.8 microg ml(-1) h(-1 )respectively. Bicarbonate (HCO(3) (-)) was used as unique carbon source. Finally, the significative oxidation capacity shown by both strains opens the way to further studies aimed at implementing biological systems to treat arsenic rich wastewater.