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RpoE fine tunes expression of a subset of SsrB-regulated virulence factors in Salmonella enterica serovar Typhimurium.

Osborne SE, Coombes BK - BMC Microbiol. (2009)

Bottom Line: The survival of Salmonella enterica within the intracellular host niche requires highly co-ordinated expression of virulence effectors predominantly regulated by the SsrAB two-component regulatory system.Mutants lacking the gene encoding the alternative sigma factor sigmaE (rpoE) are also highly attenuated for intracellular survival, pointing to a potential connection with the SsrAB regulatory system.In this study we demonstrate that RpoE is involved in fine-tuning the expression of a subset of SsrB-regulated genes found in the Salmonella pathogenicity island-2 (SPI-2) genetic locus that encodes a horizontally acquired type III secretion system, and unlinked genes integrated into this regulon that are required for virulence in host animals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Michael G DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada. osborns@mcmaster.ca

ABSTRACT

Background: The survival of Salmonella enterica within the intracellular host niche requires highly co-ordinated expression of virulence effectors predominantly regulated by the SsrAB two-component regulatory system. S. enterica serovar Typhimurium mutants lacking the ssrAB genes are avirulent in mice, highlighting the importance of this regulatory system in vivo. Mutants lacking the gene encoding the alternative sigma factor sigmaE (rpoE) are also highly attenuated for intracellular survival, pointing to a potential connection with the SsrAB regulatory system.

Results: In this study we demonstrate that RpoE is involved in fine-tuning the expression of a subset of SsrB-regulated genes found in the Salmonella pathogenicity island-2 (SPI-2) genetic locus that encodes a horizontally acquired type III secretion system, and unlinked genes integrated into this regulon that are required for virulence in host animals.

Conclusion: These data point to a potential connection between the virulence phenotype of strains lacking ssrB and rpoE, and highlight new transcriptional regulation that might be essential for appropriate temporal and spatial control of the virulence-associated type III secretion system during host infection.

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The effect of RpoE on SsrB-regulated genes is downstream of ssrAB expression. The ssrB gene in wild type and ΔrpoE cells was replaced with an ssrB-FLAG allele in its native location on the chromosome. Cells were grown under SsrB-activating conditions for six hours and lysates were probed by western blot to detect SsrB-FLAG and intracellular DnaK as a control. The data shown are representative of two experiments performed independently with identical results.
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Figure 3: The effect of RpoE on SsrB-regulated genes is downstream of ssrAB expression. The ssrB gene in wild type and ΔrpoE cells was replaced with an ssrB-FLAG allele in its native location on the chromosome. Cells were grown under SsrB-activating conditions for six hours and lysates were probed by western blot to detect SsrB-FLAG and intracellular DnaK as a control. The data shown are representative of two experiments performed independently with identical results.

Mentions: The variable effects of rpoE deletion on SsrB-regulated effectors suggested that RpoE might direct transcription downstream of ssrB expression. To test this, we replaced the ssrB gene in ΔrpoE and wild type cells with an ssrB::FLAG allele [19] and examined the levels of SsrB protein in the strains by western blot. There was no change in the levels of SsrB-FLAG between wild type and ΔrpoE cells (Figure 3), indicating that the effects of RpoE on the four classes of virulence gene promoters examined here was not mediated through changes to SsrB protein levels. Together these data establish a role for RpoE in the fine-tuning of virulence gene expression in S. Typhimurium.


RpoE fine tunes expression of a subset of SsrB-regulated virulence factors in Salmonella enterica serovar Typhimurium.

Osborne SE, Coombes BK - BMC Microbiol. (2009)

The effect of RpoE on SsrB-regulated genes is downstream of ssrAB expression. The ssrB gene in wild type and ΔrpoE cells was replaced with an ssrB-FLAG allele in its native location on the chromosome. Cells were grown under SsrB-activating conditions for six hours and lysates were probed by western blot to detect SsrB-FLAG and intracellular DnaK as a control. The data shown are representative of two experiments performed independently with identical results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2651894&req=5

Figure 3: The effect of RpoE on SsrB-regulated genes is downstream of ssrAB expression. The ssrB gene in wild type and ΔrpoE cells was replaced with an ssrB-FLAG allele in its native location on the chromosome. Cells were grown under SsrB-activating conditions for six hours and lysates were probed by western blot to detect SsrB-FLAG and intracellular DnaK as a control. The data shown are representative of two experiments performed independently with identical results.
Mentions: The variable effects of rpoE deletion on SsrB-regulated effectors suggested that RpoE might direct transcription downstream of ssrB expression. To test this, we replaced the ssrB gene in ΔrpoE and wild type cells with an ssrB::FLAG allele [19] and examined the levels of SsrB protein in the strains by western blot. There was no change in the levels of SsrB-FLAG between wild type and ΔrpoE cells (Figure 3), indicating that the effects of RpoE on the four classes of virulence gene promoters examined here was not mediated through changes to SsrB protein levels. Together these data establish a role for RpoE in the fine-tuning of virulence gene expression in S. Typhimurium.

Bottom Line: The survival of Salmonella enterica within the intracellular host niche requires highly co-ordinated expression of virulence effectors predominantly regulated by the SsrAB two-component regulatory system.Mutants lacking the gene encoding the alternative sigma factor sigmaE (rpoE) are also highly attenuated for intracellular survival, pointing to a potential connection with the SsrAB regulatory system.In this study we demonstrate that RpoE is involved in fine-tuning the expression of a subset of SsrB-regulated genes found in the Salmonella pathogenicity island-2 (SPI-2) genetic locus that encodes a horizontally acquired type III secretion system, and unlinked genes integrated into this regulon that are required for virulence in host animals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Michael G DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada. osborns@mcmaster.ca

ABSTRACT

Background: The survival of Salmonella enterica within the intracellular host niche requires highly co-ordinated expression of virulence effectors predominantly regulated by the SsrAB two-component regulatory system. S. enterica serovar Typhimurium mutants lacking the ssrAB genes are avirulent in mice, highlighting the importance of this regulatory system in vivo. Mutants lacking the gene encoding the alternative sigma factor sigmaE (rpoE) are also highly attenuated for intracellular survival, pointing to a potential connection with the SsrAB regulatory system.

Results: In this study we demonstrate that RpoE is involved in fine-tuning the expression of a subset of SsrB-regulated genes found in the Salmonella pathogenicity island-2 (SPI-2) genetic locus that encodes a horizontally acquired type III secretion system, and unlinked genes integrated into this regulon that are required for virulence in host animals.

Conclusion: These data point to a potential connection between the virulence phenotype of strains lacking ssrB and rpoE, and highlight new transcriptional regulation that might be essential for appropriate temporal and spatial control of the virulence-associated type III secretion system during host infection.

Show MeSH
Related in: MedlinePlus