ChrASO, the chromate efflux pump of Shewanella oneidensis, improves chromate survival and reduction

Abstract : The chromate efflux pump encoding gene chrA SO was identified on the chromosome of She-wanella oneidensis MR1. Although chrA SO is expressed without chromate, its expression level increases when Cr(VI) is added. When deleted, the resulting mutant ΔchrA SO exhibits a chromate sensitive phenotype compared to that of the wild-type strain. Interestingly, heter-ologous expression of chrA SO in E. coli confers resistance to high chromate concentration. Moreover, expression of chrA SO in S. oneidensis and E. coli significantly improves Cr(VI) reduction. This effect could result either from extracytoplasmic chromate reduction or from a better cell survival leading to enhanced Cr(VI) reduction.