Efficient arsenate reduction by As-resistant bacterium Bacillus sp. strain PVR-YHB1-1: Characterization and genome analysis.

Arsenate (AsV) reduction in bacteria is essential to alleviate their arsenic (As) toxicity. We isolated a Bacillus strain PVR-YHB1-1 from the roots of As-hyperaccumulator Pteris vittata. The strain was efficient in reducing AsV to arsenite (AsIII)， but the associated mechanisms were unclear. Here， we investigated its As resistance and reduction behaviors and associated genes at genome level. Results showed that the strain tolerated up to 20 mM AsV. When grown in 1 mM AsV， 96% AsV was reduced to AsIII in 48 h， with its AsV reduction ability being positively correlated to bacterial biomass. Two ars operons arsRacr3arsCDA and arsRKacr3arsC for As metabolisms were identified based on draft genome sequencing and gene annotations. Our data suggested that both operons might have attributed to efficient As resistance and AsV reduction in PVR-YHB1-1， providing clues to better understand As transformation in bacteria and their roles in As transformation in the environment.