Involvement of the oscA gene in the sulphur starvation response and in Cr(VI) resistance in Pseudomonas corrugata 28

Abstract

Pseudomonas corrugata28 is a Cr(VI)-hyper-resistant bacterium. A Cr(VI)-sensitive mutant was obtained by insertional mutagenesis using EZ-Tn5Tnp. The mutant strain was impaired in a gene, here namedoscA(organosulphurcompounds), which encoded a hypothetical small protein of unknown function. The gene was located upstream of a gene cluster that encodes the components of the sulphate ABC transporter, and it formed a transcriptional unit withsbp, which encoded the periplasmic binding protein of the transporter. TheoscA–sbptranscriptional unit was strongly and quickly overexpressed after chromate exposure, suggesting the involvement ofoscAin chromate resistance, which was further confirmed by means of a complementation experiment. Phenotype MicroArray (PM) analysis made it possible to assay 1536 phenotypes and also indicated that theoscAgene was involved in the utilization of organosulphur compounds as a sole source of sulphur. This is believed to be the first evidence thatoscAplays a role in activating a sulphur starvation response, which is required to cope with oxidative stress induced by chromate.