Arsenite-oxidizing bacteria isolated from an abandoned realgar mining area: Characterization and the influence on arsenic accumulation in rice seedlings

Abstract

Rice consumption is the main route of human exposure to arsenic (As) contamination. Oxidation of more toxic arsenite [As(III)] to less toxic arsenate [As(V)] is considered as a potential strategy to alleviate As contamination in rice plant. In this study, two As(III)-oxidizing bacterial strains SMS06 and SMS11 were isolated from the As-contaminated soils collected from an abandoned realgar mining area in Shimen County, China. According to the 16S rRNA gene sequences, SMS06 and SMS11 were affiliated with genera Achromobacter and Pseudomonas, respectively. The aioA gene was amplified in both strains while the arsB and arsM genes were not detected, indicating that the detoxification of As(III) in the strains was mainly through oxidation process governed by the aioA gene. Under aerobic condition, strains SMS06 and SMS11 could completely oxidize 600 and 450 mg/L of As(III) to As(V), respectively. The oxidation process was dependent on the bacterial growth rate. Reduction of As accumulation was observed in the rice seedlings inoculated with strain SMS06 or SMS11. The total As concentrations in the rice seedlings inoculated with the strains were decreased up to 42.0% compared to that without bacteria inoculation. The results indicated these microorganisms as potential candidates for remediation of As(III) contamination in the environment.