TRANSCRIPTIONAL CONTROL OF A Salmonella-SPECIFIC COPPER-RESISTANCE LOCUS

LÓPEZ, MARÍA C; CHECA, SUSANA K.; SONCINI, FERNANDO C.

Rosario, Santa Fe

Congreso; IX Congreso de Microbiología General; 2013

Sociedad Argentina de Microbiología General (SAMIGE)

Heavy metal ions such as zinc, iron, and copper, are required in trace amounts for bacterial growth yet they are toxic when present in excess. Toxicity occurs through a variety of mechanisms, including binding to free thiol groups, disrupting protein structure or function; displacing essential metal cofactors in proteins, or generating reactive oxygen species. Gram negative bacteria have several resources to cope with heavy metal stress that allow them to thrive in ecosystems contaminated with heavy metals. In Salmonella enterica serovar Typhimurium, the main player in the resistance to copper is the cue regulon. Expression of this regulon is controlled by CueR, a Cu-sensor that modulates the transcription of several copper-resistance factors. Here we report the characterization of another locus involved in resistance to the metal ion. We observed the induction of the Salmonella-specific suppressor of copper sensitivity (scs) operon in the presence of copper. This locus consists of genes coding for proteins with thioredoxin-like CXXC motifs. Our results indicate that this locus is required for copper-resistance because a mutant with a deletion of the entire operon was more sensitive to Cu that the wild-type strain. Using bioinformatics, real-time PCR and Western blot experiments with chromosomally encoded 3xFLAG tagged gene-products, and different mutant strains we localized a putative copper-responsive element in the promoter region of the scsABCD operon and identified a signal-transduction system responsible for this control. Overall, these results show that the products of the scsABCD operon are essential for the maintenance of a proper envelope homeostasis to deal with copper excess.