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Listeria monocytogenes sigmaB modulates PrfA-mediated virulence factor expression.

ABSTRACT: Listeria monocytogenes sigma(B) and positive regulatory factor A (PrfA) are pleiotropic transcriptional regulators that coregulate a subset of virulence genes. A positive regulatory role for sigma(B) in prfA transcription has been well established; therefore, observations of increased virulence gene expression and hemolytic activity in a DeltasigB strain initially appeared paradoxical. To test the hypothesis that L. monocytogenes sigma(B) contributes to a regulatory network critical for appropriate repression as well as induction of virulence gene expression, genome-wide transcript profiling and follow-up quantitative reverse transcriptase PCR (qRT-PCR), reporter fusion, and phenotypic experiments were conducted using L. monocytogenes prfA*, prfA* DeltasigB, DeltaprfA, and DeltaprfA DeltasigB strains. Genome-wide transcript profiling and qRT-PCR showed that in the presence of active PrfA (PrfA*), sigma(B) is responsible for reduced expression of the PrfA regulon. sigma(B)-dependent modulation of PrfA regulon expression reduced the cytotoxic effects of a PrfA* strain in HepG2 cells, highlighting the functional importance of regulatory interactions between PrfA and sigma(B). The emerging model of the role of sigma(B) in regulating overall PrfA activity includes a switch from transcriptional activation at the P2(prfA) promoter (e.g., in extracellular bacteria when PrfA activity is low) to posttranscriptional downregulation of PrfA regulon expression (e.g., in intracellular bacteria when PrfA activity is high).

SUBMITTER: Ollinger J

PROVIDER: S-EPMC2681731 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Listeria monocytogenes sigmaB modulates PrfA-mediated virulence factor expression.

Ollinger Juliane J Bowen Barbara B Wiedmann Martin M Boor Kathryn J KJ Bergholz Teresa M TM

Infection and immunity 20090302 5

Listeria monocytogenes sigma(B) and positive regulatory factor A (PrfA) are pleiotropic transcriptional regulators that coregulate a subset of virulence genes. A positive regulatory role for sigma(B) in prfA transcription has been well established; therefore, observations of increased virulence gene expression and hemolytic activity in a DeltasigB strain initially appeared paradoxical. To test the hypothesis that L. monocytogenes sigma(B) contributes to a regulatory network critical for appropri ...[more]

PMID: 19255187

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Project description:Listeria monocytogenes is able to efficiently utilize glycerol as a carbon source. In a defined minimal medium, the growth rate (during balanced growth) in the presence of glycerol is similar to that in the presence of glucose or cellobiose. Comparative transcriptome analyses of L. monocytogenes showed high-level transcriptional upregulation of the genes known to be involved in glycerol uptake and metabolism (glpFK and glpD) in the presence of glycerol (compared to that in the presence of glucose and/or cellobiose). Levels of expression of the genes encoding a second putative glycerol uptake facilitator (GlpF(2)) and a second putative glycerol kinase (GlpK(2)) were less enhanced under these conditions. GlpK(1) but not GlpK(2) was essential for glycerol catabolism in L. monocytogenes under extracellular conditions, while the loss of GlpK(1) affected replication in Caco-2 cells less than did the loss of GlpK(2) and GlpD. Additional genes whose transcription levels were higher in the presence of glycerol than in the presence of glucose and cellobiose included those for two dihydroxyacetone (Dha) kinases and many genes that are under carbon catabolite repression control. Transcriptional downregulation in the presence of glycerol (compared to those in the presence glucose and cellobiose) was observed for several genes and operons that are positively regulated by glucose, including genes involved in glycolysis, N metabolism, and the biosynthesis of branched-chain amino acids. The highest level of transcriptional upregulation was observed for all PrfA-dependent genes during early and late logarithmic growth in glycerol. Under these conditions, a low level of HPr-Ser-P and a high level of HPr-His-P were present in the cells, suggesting that all enzyme IIA (EIIA) (or EIIB) components of the phosphotransferase system (PTS) permeases expressed will be phosphorylated. These and other data suggest that the phosphorylation state of PTS permeases correlates with PrfA activity.

Dataset Information

Listeria monocytogenes sigmaB modulates PrfA-mediated virulence factor expression.

Publications

Listeria monocytogenes sigmaB modulates PrfA-mediated virulence factor expression.

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