Identification and analysis of ars genes in strains of Bacillus hyper tolerant to arsenic, isolated from thermal pools in Araró, Mexico

Abstract

In this work we investigated the presence, diversity and phylogenetic relationships of genes that confer resistance to arsenic (As) in 37 strains of the genus Bacillus, isolated from microbial mats in hot springs from Araró, Michoacán, Mexico. Specific oligonucleotides were designed for PCR amplification of the genes arsB (arsenite-specific efflux pump) and arsC (arsenite reductase), ACR3 (arsenite transporter) and aoxB (arsenite oxidase) of the genus Bacillus, detecting only the genes arsB and arsC in 21 out of the 37  analyzed strains (56.7% of the total). The Blastx-type analysis showed a high identity (84-100%) with arsenite efflux pumps (ArsB) and arsenate reductase proteins (ArsC) of various strains of the genera Bacillus, Paenibacillus, Psychrobacter and Planococcus. Such analyzes were confirmed through the construction of phylogenies of the arsB and arsC sequences. The detection of the arsB and arsC genes in Bacillus strains was correlated with As hyperresistance values, which corresponded up to 32 and 128 mM of arsenite (III) and arsenate (V), respectively. Finally, the arsB and arsC genes identified in Bacillus strains could be a mechanism of resistance to As in an extreme aquatic environment, such as in  Araro’s hot springs.