Comparison of arsenate reduction and release by three As(V)-reducing bacteria isolated from arsenic-contaminated soil of Inner Mongolia, China

Arsenic (As) contamination has become a worldwide environmental problem: arsenite (As(Ⅲ)) especially has posed a major threat to human health. Here, we report the first three isolates of anaerobic As(Ⅴ)-reducing bacterial strains (strains JQ, DJ-3 and DJ-4) from a soil sample containing 48.7% of total As in the form of As(III) collected in Chifeng, Inner Mongolia, China. Strains JQ, DJ-3 and DJ-4 were phylogenetically closely related to Bacillus, Desulfitobacterium and Exiguobacterium, respectively. Among these strains, JQ and DJ-3 have the arsC gene, DJ-4 possesses the arrA gene. The three strains could all resist and reduce high concentrations of As(Ⅴ) under anoxic conditions. The order of resistance to As(Ⅴ) was DJ-3 > JQ > DJ-4. Strain DJ-3 not only possesses the strongest resistance to As(Ⅴ) but could also reduce 53% of the As(Ⅴ) to As(III) in the treatment of 60 mM As(Ⅴ) in 5 d. All three strains could release As from goethite; strain DJ-4 has the highest ability to promote the release of As (90.5%) from goethite. These results suggested that strains JQ, DJ-3 and DJ-4 may play an important role in the mobilization and transformation of As in soil. •We isolated three anaerobic As(Ⅴ)-reducing bacterium from soil with high ratio of As(Ⅲ).•Strains JQ, DJ-3 and DJ-4 could transform very high concentration of As(Ⅴ) to As(Ⅲ).•All the three strains could release goethite-adsorbed As(Ⅴ) into solution.•We compared the three strains with other previously isolated strains.•The existence of the strains will cause the mobilization and transformation of As in soil. Three As(Ⅴ)-reducing bacteria isolated from soil with high levels of As(Ⅲ) have a strong ability to reduce dissolved As(Ⅴ) and release solid As(Ⅴ), which will cause As(Ⅲ) pollution of the soil.