Copper stress targets the Rcs system to induce Salmonella enterica multiaggregative behavior

PONTEL, L. B.; PEZZA, A.; SONCINI, F. C.

Puerto Madryn

Congreso; 46 Annual Meeting; 2010

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Copper is an essential cofactor required for a variety of cellular processes such as hydrolytic pathways, iron transport, respiration and defense against oxidative stress. However, it is also highly toxic and in consequence its intracellular concentration must be tightly controlled. Gram-negative bacteria rely on the cue regulon to regulate the intracellular copper concentration. In Salmonella the regulon is composed by genes coding for a MerR-like transcriptional regulator, CueR, an inner membrane copperexporter, CopA, and two periplasmic proteins: the multicopper oxidase CuiD, and CueP, a copper-binding protein. We observed that cuiD strains form mucoid colonies on sublethal coppercontaining solid media. We showed that this multiaggregative behavior is caused by the induction of extracellular colanic acidpolysaccharide in an Rcs phosphorelay-dependent manner and that Cu promoted the induction of the Rcs system in the cuiD strain. Expression of CuiD or of CueP abrogated the mucoid phenotype and repressed the Cu-dependent expression of the colanic acid biosynthetic operon, suggesting a role for CueP in alleviating the toxic effect of Cu-overloading by counteracting the mechanism that activates Rcs. We propose that the Rcs-dependent expression of exopolysaccharides is a defense mechanism to cope with Cu toxicity in conditions where the cue regulon is overcome.