Genetic Identification of Antimonate Respiratory Reductase in Shewanella 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 Shewanella sp. ANA-3 through an arsenate respiratory reductase encoded by arrAB. Incubation experiments showed that Shewanella 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 arrAB was highly expressed in Sb­(V)-respiring reduction. In vivo evidence with mutants indicated that neither ANA-3-ΔarrA nor ANA-3-ΔarrB was capable of reducing Sb­(V) as efficiently as the wild type, whereas complementation by the wild-type sequences of arrA and arrB 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 luxS gene. This study opens a new chapter in the mechanistic understanding of microbial Sb­(V) respiratory reduction.