The ars genotype characterization of arsenic-resistant bacteria from arsenic-contaminated gold-silver mines in the Republic of Korea.

The isolates were identified on the basis of ars genotype characteristics as well as arsenic oxidation/reduction analysis based on the molecular detection characterization. Diversity, pH range (4.0 to 7.0), location, and ars features were assessed for four arsenic-contaminated pond sites and six arsenic tailings located in the Duck-um mine and Myoung-bong mine areas. The presence of ars genes in the genomes of each bacterial strain was evaluated using polymerase chain reaction. Batch experiment results showed that Pseudomonas putida strains OS-3 and -18 completely oxidized 1 mM of arsenite(III) to arsenate(V) within 35-40 h. In contrast, two arsenate-reducing bacteria isolated from mines, P. putida RS-4 and RS-5, were capable of growing aerobically in growth medium supplemented with up to 66.7 mM arsenate(V), which are significantly higher concentration than those tolerated by other arsenic-resistant bacteria. These results suggest that newly isolated indigenous arsenic-resistant bacteria may provide a better understanding of the molecular geomicrobiology and may be applied to the bioremediation of arsenic-contaminated mines in Korea. Ecologically, the redox potential plays an important role in arsenic toxicity and mobility in As-contaminated mine areas, as it facilitates the biogeochemical cycling activity of Pseudomonas sp. groups.