Genetic Identification of Antimonate Respiratory Reductase in sp. ANA-3.

Microbial antimonate [Sb(V)] respiratory reduction is an important process regulating Sb redox transformation in the environment. However, little is known about the microbial respiratory reductase for Sb(V). Herein, we report Sb(V)-respiring reduction by sp. ANA-3 through an arsenate respiratory reductase encoded by . Incubation experiments showed that sp. ANA-3 mediated Sb(V)-respiring reduction, which was dependent on the cell concentration. Both protein analysis and reverse transcriptase-polymerase chain reaction results revealed that was highly expressed in Sb(V)-respiring reduction. In vivo evidence with mutants indicated that neither ANA-3-Δ nor ANA-3-Δ was capable of reducing Sb(V) as efficiently as the wild type, whereas complementation by the wild-type sequences of and rescued the mutants' ability. Our in vitro results showed that ArrAB purified by His-Tag was able to mediate Sb(V) reduction, though with much suppressed catalytic kinetics compared with As(V) reduction. The cell-concentration-dependent reduction of Sb(V) was regulated by quorum sensing via the gene. This study opens a new chapter in the mechanistic understanding of microbial Sb(V) respiratory reduction.