CpxR/CpxA Controls scsABCD Transcription To Counteract Copper and Oxidative Stress in Salmonella enterica Serovar Typhimurium

Abstract

Copper intoxication triggers both specific and nonspecific responses in Salmonella . The scs locus, which codes for periplasmic thiol/disulfide-oxidoreductase/isomerase-like proteins, has been the focus of attention because it is necessary for copper resistance, oxidative stress responses, and virulence and because it is not present in nonpathogenic Escherichia coli . Still, the conditions under which the scs locus is expressed and the roles of its individual components remain unknown. In this report, we examine the contribution of each Scs factor to survival under H 2 O 2 and copper stress. We establish that the scs genes form a copper-activated operon controlled by the CpxR/CpxA signal transduction system, and we provide evidence of its conserved gene arrangement and regulation in other bacterial pathogens.