COMPLEX REGULATION OF THE Salmonella-SPECIFIC CBA EFFLUX PUMP gesABC

DAVID, ALDANA; CERMINATI, SEBASTIÁN; CHECA, SUSANA K.; SONCINI, FERNANDO C.

Rosario, Santa Fe

Congreso; IX Congreso de Microbiología General; 2013

Sociedad Argentina de Microbiología General (SAMIGE)

Salmonella employs a specific set of proteins that allows the detection of gold in the environment and to mount the proper response to this injury. This includes a P-type ATPase, GolT, a small cytoplasmic metal binding protein, GolB and a CBA efflux system GesABC. Their genes are transcriptionally induced in the presence of gold ions by the Au-sensor GolS. We have previously characterized the GolS-dependent operator at the promoter of gesABC and detected differences with the other GolS-controlled genes that results in its delayed expression in the presence of Au ions. Besides its essential role in Au-resistance, the GesABC system can also mediate the resistance of xenobiotics in a strain deleted in the main drug transporter AcrAB, suggesting additional detoxification roles. Using bioinformatics we were able to identified putative regulatory sequences at the gesABC promoter, as well as post-transcriptional regulatory sequences at its 5´-untraslated region. Effective regulation of GesABC expression was verified by the analysis of reporter constructions in strains deleted of different stress-regulatory systems and by phenotypic characterization of these strains. Specific regulators interactions were verified by mapping of the binding sequence either by electrophoresis mobility shift assays or by footprinting assays and corroborated by site-directed mutagenesis, confirming the tight expression control exerted on this Salmonella-specific detoxification system by different stress-induced regulators. The results obtained here indicate that different regulatory strategies contribute to fine-tuning the expression of GesABC in order to guarantee the proper supply of this efflux pump under different stress conditions.