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Journal of Bacteriology, October 2007, p. 7335-7342, Vol. 189, No. 20
0021-9193/07/$08.00+0     doi:10.1128/JB.00801-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Induction of RpoS Degradation by the Two-Component System Regulator RstA in Salmonella enterica{triangledown}

María L. Cabeza, Andrés Aguirre, Fernando C. Soncini, and Eleonora García Véscovi*

Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, S2002LRK Rosario, Argentina

Received 23 May 2007/ Accepted 7 August 2007

Bacterial survival in diverse and changing environments relies on the accurate interplay between different regulatory pathways, which determine the design of an adequate adaptive response. The proper outcome depends on a precise gene expression profile generated from the finely tuned and concerted action of transcriptional factors of distinct regulatory hierarchies. Salmonella enterica serovar Typhimurium harbors multiple regulatory systems that are crucial for the bacterium to cope with harsh extra- and intracellular environments. In this work, we found that the expression of Salmonella RstA, a response regulator from the two-component system family, was able to downregulate the expression of three RpoS-controlled genes (narZ, spvA, and bapA). Furthermore, this downregulation was achieved by a reduction in RpoS cellular levels. The alternative sigma factor RpoS is critical for bacterial endurance under the most-stressful conditions, including stationary-phase entrance and host adaptation. Accordingly, RpoS cellular levels are tightly controlled by complex transcriptional, translational, and posttranslational mechanisms. The analysis of each regulatory step revealed that in Salmonella, RstA expression was able to promote RpoS degradation independently of the MviA-ClpXP proteolytic pathway. Additionally, we show that RstA is involved in modulating Salmonella biofilm formation. The fact that the RpoS-modulated genes affected by RstA expression have previously been demonstrated to contribute to Salmonella pathogenic traits, which include biofilm-forming capacity, suggests that under yet unknown conditions, RstA may function as a control point of RpoS-dependent pathways that govern Salmonella virulence.

* Corresponding author. Mailing address: Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR), Departamento de Microbiología, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Suipacha 531, (S2002LRK) Rosario, Argentina. Phone: 54-341-4356369. Fax: 54-341-4804598. E-mail: garciavescovi{at}ibr.gov.ar

{triangledown} Published ahead of print on 17 August 2007.

Journal of Bacteriology, October 2007, p. 7335-7342, Vol. 189, No. 20
0021-9193/07/$08.00+0     doi:10.1128/JB.00801-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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