DNA sequence homology analysis of ars genes in arsenic-resistant bacteria

Homology of ars (arsenic-resistance system) genes was examined among the indigenous bacteria isolated from the soils and sediments of two abandoned Au mines, which are highly contaminated with arsenic. The DNA and amino acid sequence homology of the ars determinants were investigated using an ars genotype. The isolated strains showed As(III)-oxidation ability contained arsAB genes encoding the efflux pump as well as arsR and arsD regulator genes. The arsR and arsD leader gene are required for an arsenic resistance system when the high-homology genes (arsR; pI258 52.09% and arsD; Shewanell sp. 42.33%) are controlled by the ars inducer-independent regulatory amino acid sequence. These leader gene were observed under weak acidic conditions in the Myoung-bong (pH; 5.0 to 6.0) and Duck-um (pH; 4.0 to 7.0) mines. In addition, the strains with the ability of As(V)-reduction involved the arsC gene homologues, as in the strain OW-16 (Pseudomonas putida). The arsenic-resistance genes in the isolated indigenous bacteria showed varying degrees of amino acid similarity to the homologous genes found in the database (GenBank) such as P. putida KT2440: 39-53% for arsR, 22-42% for arsD, 16-84% for arsA, 26-45% for arsB, 17-44% for arsAB, 37-41% for arsC, and 14-47% for arsH. These findings suggested that the function of the various ars gene in indigenous bacteria existing in weakly oxidative conditions may be the key factor for redox mechanisms and biogeochemical systems in arsenic contaminated soils.