Limits...
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.

Show MeSH

Related in: MedlinePlus

The transcriptional activity of SsrB-regulated virulence genes is affected by an rpoE deletion. Wild type and ΔrpoE cells carrying single-copy chromosomal transcriptional reporters of (A) PsseA::pPsseA-lacZ, (B) PssaB::pPssaB-lacZ, (C) PssaG::pPssaG-lacZ, (D) PsifA::pPsifA-lacZ, (E) PsseL::pPsseL-lacZ and (F) PsrfN::pPsrfN-lacZ were grown in LPM (pH 5.8). At the indicated time β-galactosidase activity was measured and expressed as relative light units (RLU) normalized to optical density of the culture. Wild type and ΔrpoE cells lacking the transcriptional reporters were used as controls in each experiment. Data are the means with standard error from triplicate determinations from three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2651894&req=5

Figure 2: The transcriptional activity of SsrB-regulated virulence genes is affected by an rpoE deletion. Wild type and ΔrpoE cells carrying single-copy chromosomal transcriptional reporters of (A) PsseA::pPsseA-lacZ, (B) PssaB::pPssaB-lacZ, (C) PssaG::pPssaG-lacZ, (D) PsifA::pPsifA-lacZ, (E) PsseL::pPsseL-lacZ and (F) PsrfN::pPsrfN-lacZ were grown in LPM (pH 5.8). At the indicated time β-galactosidase activity was measured and expressed as relative light units (RLU) normalized to optical density of the culture. Wild type and ΔrpoE cells lacking the transcriptional reporters were used as controls in each experiment. Data are the means with standard error from triplicate determinations from three independent experiments.

Mentions: In wild type cells, promoter activity from all the transcriptional fusions was high, as expected, because LPM medium is highly inducing for SsrB activity [21]. In contrast, promoter activity for sseA, ssaB, and sifA decreased in the rpoE mutant compared to wild type cells (Figure 2A, B and 2D), whereas promoter activity from the ssaG and srfN reporters was upregulated in the rpoE mutant (Figure 2C and 2F). β-galactosidase activity observed from the sseL reporter was unaltered in the rpoE deletion compared to that in wild type cells (Figure 2E). These data are consistent with the protein levels detected for these gene products. Together, these data indicate that σE can have a variable and bidirectional effect on SsrB-regulated virulence genes.


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 transcriptional activity of SsrB-regulated virulence genes is affected by an rpoE deletion. Wild type and ΔrpoE cells carrying single-copy chromosomal transcriptional reporters of (A) PsseA::pPsseA-lacZ, (B) PssaB::pPssaB-lacZ, (C) PssaG::pPssaG-lacZ, (D) PsifA::pPsifA-lacZ, (E) PsseL::pPsseL-lacZ and (F) PsrfN::pPsrfN-lacZ were grown in LPM (pH 5.8). At the indicated time β-galactosidase activity was measured and expressed as relative light units (RLU) normalized to optical density of the culture. Wild type and ΔrpoE cells lacking the transcriptional reporters were used as controls in each experiment. Data are the means with standard error from triplicate determinations from three independent experiments.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: The transcriptional activity of SsrB-regulated virulence genes is affected by an rpoE deletion. Wild type and ΔrpoE cells carrying single-copy chromosomal transcriptional reporters of (A) PsseA::pPsseA-lacZ, (B) PssaB::pPssaB-lacZ, (C) PssaG::pPssaG-lacZ, (D) PsifA::pPsifA-lacZ, (E) PsseL::pPsseL-lacZ and (F) PsrfN::pPsrfN-lacZ were grown in LPM (pH 5.8). At the indicated time β-galactosidase activity was measured and expressed as relative light units (RLU) normalized to optical density of the culture. Wild type and ΔrpoE cells lacking the transcriptional reporters were used as controls in each experiment. Data are the means with standard error from triplicate determinations from three independent experiments.
Mentions: In wild type cells, promoter activity from all the transcriptional fusions was high, as expected, because LPM medium is highly inducing for SsrB activity [21]. In contrast, promoter activity for sseA, ssaB, and sifA decreased in the rpoE mutant compared to wild type cells (Figure 2A, B and 2D), whereas promoter activity from the ssaG and srfN reporters was upregulated in the rpoE mutant (Figure 2C and 2F). β-galactosidase activity observed from the sseL reporter was unaltered in the rpoE deletion compared to that in wild type cells (Figure 2E). These data are consistent with the protein levels detected for these gene products. Together, these data indicate that σE can have a variable and bidirectional effect on SsrB-regulated virulence genes.

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