The Salmonella enterica RstA/RstB system and the RpoS dependent response

CABEZA, M. L.; SONCINI, F. C.; GARCÍA VÉSCOVI, E.

Pinamar

Congreso; 42th Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2005

Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular

In S. typhimurium the PhoP/PhoQ two-component system governs the adaptation to Mg2+ limited-media, and controls essential pathogenic properties. We determined that the expression of another two-component system, RstA/RstB is under Mg2+-controlled, PhoP-dependent transcriptional regulation in Salmonella. We found that the expression of narZ, spvA and STM2689 is down-regulated and that the expression of STM2195 is up-regulated by RstA, when this regulador is over-expressed. Overproduction of this protein may be simulating its active form, in experimental conditions where its specific signal may be absent. We verified that the expression of RstA downregulated genes is also dependent on RpoS, and that the expression of STM2196 (the only RstA regulated gene) is not dependent on this sigma factor. We showed that regulation of our mutants is not due to a transcriptional regulatory effect of RpoS on rstA and we also demostrated that rpoS is not under transcriptional control of RstA. Finally, we showed that RstA post-transcriptionally lowers RpoS cellular levels when RstA is overproduced.  In this way, RstA may be sensing an environmental stimuli that results in its own dependent genes activity regulation and also in the modulation of those RpoS- dependent. These results add a novel point of control in the complex RpoS regulation network