Identification of Antimony- and Arsenic-Oxidizing Bacteria Associated with Antimony Mine Tailing

Antimony (Sb) is a naturally occurring toxic element commonly associated with arsenic (As) in the environment and both elements have similar chemistry and toxicity. Increasing numbers of studies have focused on microbial As transformations, while microbial Sb interactions are still not well understood. To gain insight into microbial roles in the geochemical cycling of Sb and As, soils from Sb mine tailing were examined for the presence of Sb- and As-oxidizing bacteria. After aerobic enrichment culturing with As-III (10 mM) or Sb-III (100 mu M), pure cultures of Pseudomonas-and Stenotrophomonas-related isolates with Sb-III oxidation activities and a Sinorhizobium-related isolate capable of As-III oxidation were obtained. The As-III-oxidizing Sinorhizobium isolate possessed the aerobic arsenite oxidase gene (aioA), the expression of which was induced in the presence of As-III or Sb-III. However, no Sb-III oxidation activity was detected from the Sinorhizobium-related isolate, suggesting the involvement of different mechanisms for Sb and As oxidation. These results demonstrate that indigenous microorganisms associated with Sb mine soils are capable of Sb and As oxidation, and potentially contribute to the speciation and mobility of Sb and As in situ.