Microbial arsenic (As) transformation is important in As biogeochemical cycles in the environment. More and more bacteria capable of As transformation have been reported. In this study, a new As-resistant bacterial strain Leclercia adecarboxylata As3-1 was isolated and its associated mechanisms in As resistance and detoxification were evaluated based on genome sequencing and gene annotations. After subjecting strain As3-1 to media containing arsenate (AsV), AsV reduction occurred and an AsV-enhanced bacterial growth was observed. In contrast, strain As3-1 lacked arsenite (AsIII) oxidation ability and displayed lower AsIII resistance than AsV, probably due to its higher AsIII accumulation. Polymerase chain reaction and phylogenic analysis showed that strain As3-1 harbored a typical AsV reductase gene (arsC) on the plasmids. Genome sequencing and gene annotations identified four operons phoUpstBACS, arsHRBC, arsCRDABC and ttrRSBCA, with additional 8 genes outside the operons that might have involved in As resistance and detoxification in strain As3-1. Among which, 5 arsC genes were found, explaining why strain As-1 tolerated high AsV concentrations. Besides ArsC, TtrB, TtrC and TtrA proteins could also be involved in AsV reduction and consequent energy acquisition for bacterial growth. Our data provided a new example of diverse As-regulating systems and AsV-enhanced growth without ArrA in bacteria, which helps to better understand the role of As in selecting microbial systems that can transform and utilize As.