Effect of the rcsB regulator expressed from different promoters, in Salmonella typhimurium virulence.

MARÍA DE LAS MERCEDES PESCARETTI; ROBERTO MORERO; MÓNICA A. DELGADO

Villa Carlos Paz-Córdba (Argentina)

Congreso; XLIV Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology (SAIB); 2008

Argentine Society for Biochemistry and Molecular Biology (SAIB)

The Rcs phosphorelay system consisting of the sensor RcsC, the response regulator RcsB, and the histidine-containing phosphotransfer protein RcsD, an intermediary in the phosphoryl transfer from RcsC to RcsB. Although the signal activating the system remains unidentified, the activation can occurs under certain growth conditions. Previously, we demonstrated that the RcsB overproduction promotes the Rcs system activation, in rcsC or rcsD mutants, but not in the double mutant rcsD rcsC, suggesting that RcsC or RcsD can independently transfer the phosphate group to RcsB. On the other hand, we found that rcsB is expressed under the control of two promoters, PrcsDB and PrcsB, and that the rcsB overexpression negatively regulates the Rcs system repressing the PrcsDB activity. Here, we show that the levels of rcsB expression from each promoter are required at different growth phase and different levels to control specific physiological process. In this way, the rcsB expression from PrcsB activity is required to maintain the repression of the RcsB-dependent motility phenotype. Also we observed a differential requirement of rcsB from PrcsDB or PrcsB activity during the phagocytosis and replication in macrophages. Taken together, our findings enhance the phosphorelay pathway and the biological significance of the Rcs system activation in Salmonella pathogenesis.