scholarly journals The response regulator ResD modulates virulence gene expression in response to carbohydrates in Listeria monocytogenes

2006 ◽  
Vol 61 (6) ◽  
pp. 1622-1635 ◽  
Author(s):  
Marianne H. Larsen ◽  
Birgitte H. Kallipolitis ◽  
Janne K. Christiansen ◽  
John E. Olsen ◽  
Hanne Ingmer
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Response Regulator ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals Use of a Phosphorylation Site Mutant To Identify Distinct Modes of Gene Repression by the Control of Virulence Regulator (CovR) in Streptococcus pyogenes

2017 ◽  
Vol 199 (18) ◽  
Author(s):  
Nicola Horstmann ◽  
Pranoti Sahasrabhojane ◽  
Hui Yao ◽  
Xiaoping Su ◽  
Samuel A. Shelburne
Keyword(s):  
Gene Expression ◽  
Streptococcus Pyogenes ◽  
Response Regulator ◽  
Phosphorylation Site ◽  
Virulence Gene ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Superficial Skin ◽  
Virulence Regulator ◽  
The Impact

ABSTRACT Control of the virulence regulator/sensor kinase (CovRS) two-component system (TCS) serves as a model for investigating the impact of signaling pathways on the pathogenesis of Gram-positive bacteria. However, the molecular mechanisms by which CovR, an OmpR/PhoB family response regulator, controls virulence gene expression are poorly defined, partly due to the labile nature of its aspartate phosphorylation site. To better understand the regulatory effect of phosphorylated CovR, we generated the phosphorylation site mutant strain 10870-CovR-D53E, which we predicted to have a constitutive CovR phosphorylation phenotype. Interestingly, this strain showed CovR activity only for a subset of the CovR regulon, which allowed for classification of CovR-influenced genes into D53E-regulated and D53E-nonregulated groups. Inspection of the promoter sequences of genes belonging to each group revealed distinct promoter architectures with respect to the location and number of putative CovR-binding sites. Electrophoretic mobility shift analysis demonstrated that recombinant CovR-D53E protein retains its ability to bind promoter DNA from both CovR-D53E-regulated and -nonregulated groups, implying that factors other than mere DNA binding are crucial for gene regulation. In fact, we found that CovR-D53E is incapable of dimerization, a process thought to be critical to OmpR/PhoB family regulator function. Thus, our global analysis of CovR-D53E indicates dimerization-dependent and dimerization-independent modes of CovR-mediated repression, thereby establishing distinct mechanisms by which this critical regulator coordinates virulence gene expression. IMPORTANCE Streptococcus pyogenes causes a wide variety of diseases, ranging from superficial skin and throat infections to life-threatening invasive infections. To establish these various disease manifestations, Streptococcus pyogenes requires tightly coordinated production of its virulence factor repertoire. Here, the response regulator CovR plays a crucial role. As an OmpR/PhoB family member, CovR is activated by phosphorylation on a conserved aspartate residue, leading to protein dimerization and subsequent binding to operator sites. Our transcriptome analysis using the monomeric phosphorylation mimic mutant CovR-D53E broadens this general notion by revealing dimerization-independent repression of a subset of CovR-regulated genes. Combined with promoter analyses, these data suggest distinct mechanisms of CovR transcriptional control, which allow for differential expression of virulence genes in response to environmental cues.

scholarly journals Listeria monocytogenes σB Modulates PrfA-Mediated Virulence Factor Expression

2009 ◽  
Vol 77 (5) ◽  
pp. 2113-2124 ◽  
Author(s):  
Juliane Ollinger ◽  
Barbara Bowen ◽  
Martin Wiedmann ◽  
Kathryn J. Boor ◽  
Teresa M. Bergholz
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Transcriptional Activation ◽  
Virulence Gene ◽  
Transcript Profiling ◽  
Virulence Gene Expression ◽  
Qrt Pcr ◽  
Genome Wide

ABSTRACT Listeria monocytogenes σB and positive regulatory factor A (PrfA) are pleiotropic transcriptional regulators that coregulate a subset of virulence genes. A positive regulatory role for σB in prfA transcription has been well established; therefore, observations of increased virulence gene expression and hemolytic activity in a ΔsigB strain initially appeared paradoxical. To test the hypothesis that L. monocytogenes σB 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* ΔsigB, ΔprfA, and ΔprfA ΔsigB strains. Genome-wide transcript profiling and qRT-PCR showed that in the presence of active PrfA (PrfA*), σB is responsible for reduced expression of the PrfA regulon. σB-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 σB. The emerging model of the role of σB 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).

scholarly journals Identification of an Orphan Response Regulator Required for the Virulence of Francisella spp. and Transcription of Pathogenicity Island Genes

2007 ◽  
Vol 75 (7) ◽  
pp. 3305-3314 ◽  
Author(s):  
Nrusingh P. Mohapatra ◽  
Shilpa Soni ◽  
Brian L. Bell ◽  
Richard Warren ◽  
Robert K. Ernst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mutant Strain ◽  
Lipid A ◽  
Response Regulator ◽  
Model Organism ◽  
Virulence Gene ◽  
Pathogenicity Island ◽  
Effective Vaccine ◽  
Gene Encoding ◽  
Virulence Gene Expression

ABSTRACT Francisella tularensis is a category A agent of biowarfare/biodefense. Little is known about the regulation of virulence gene expression in Francisella spp. Comparatively few regulatory factors exist in Francisella, including those belonging to two-component systems (TCS). However, orphan members of typical TCS can be identified. To determine if orphan TCS members affect Francisella gene expression, a gene encoding a product with high similarity to the Salmonella PmrA response regulator (FTT1557c/FNU0663.2) was deleted in Francisella novicida (a model organism for F. tularensis). The F. novicida pmrA mutant was defective in survival/growth within human and murine macrophage cell lines and was 100% defective in virulence in mice at a dose of up to 108 CFU. In addition, the mutant strain demonstrated increased susceptibility to antimicrobial peptide killing, but no differences were observed between the lipid A of the mutant and the parental strain, as has been observed with pmrA mutants of other microbes. The F. novicida pmrA mutant was 100% protective as a single-dose vaccine when challenge was with 106 CFU of F. novicida but did not protect against type A Schu S4 wild-type challenge. DNA microarray analysis identified 65 genes regulated by PmrA. The majority of these genes were located in the region surrounding pmrA or within the Francisella pathogenicity island (FPI). These FPI genes are also regulated by MglA, but MglA does not regulate pmrA, nor does PmrA regulate MglA. Thus, the orphan response regulator PmrA is an important factor in controlling virulence in F. novicida, and a pmrA mutant strain is an effective vaccine against homologous challenge.

scholarly journals Listeria monocytogenes σB Regulates Stress Response and Virulence Functions

2003 ◽  
Vol 185 (19) ◽  
pp. 5722-5734 ◽  
Author(s):  
Mark J. Kazmierczak ◽  
Sharon C. Mithoe ◽  
Kathryn J. Boor ◽  
Martin Wiedmann
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Stress Response ◽  
Consensus Sequence ◽  
Virulence Gene ◽  
Wild Type ◽  
Promoter Regions ◽  
Virulence Gene Expression ◽  
Stress Response Genes ◽  
In The Wild

ABSTRACT While the stress-responsive alternative sigma factor σB has been identified in different species of Bacillus, Listeria, and Staphylococcus, theσ B regulon has been extensively characterized only in B. subtilis. We combined biocomputing and microarray-based strategies to identify σB-dependent genes in the facultative intracellular pathogen Listeria monocytogenes. Hidden Markov model (HMM)-based searches identified 170 candidateσ B-dependent promoter sequences in the strain EGD-e genome sequence. These data were used to develop a specialized, 208-gene microarray, which included 166 genes downstream of HMM-predicted σB-dependent promoters as well as selected virulence and stress response genes. RNA for the microarray experiments was isolated from both wild-type and ΔsigB null mutant L. monocytogenes cells grown to stationary phase or exposed to osmotic stress (0.5 M KCl). Microarray analyses identified a total of 55 genes with statistically significantσ B-dependent expression under the conditions used in these experiments, with at least 1.5-fold-higher expression in the wild type over the sigB mutant under either stress condition (51 genes showed at least 2.0-fold-higher expression in the wild type). Of the 55 genes exhibiting σB-dependent expression, 54 were preceded by a sequence resembling the σB promoter consensus sequence. Rapid amplification of cDNA ends-PCR was used to confirm the σB-dependent nature of a subset of eight selected promoter regions. Notably, theσ B-dependent L. monocytogenes genes identified through this HMM/microarray strategy included both stress response genes (e.g., gadB, ctc, and the glutathione reductase gene lmo1433) and virulence genes (e.g., inlA, inlB, and bsh). Our data demonstrate that, in addition to regulating expression of genes important for survival under environmental stress conditions, σB also contributes to regulation of virulence gene expression in L. monocytogenes. These findings strongly suggest thatσ B contributes to L. monocytogenes gene expression during infection.

scholarly journals Carbon‐source regulation of virulence gene expression in Listeria monocytogenes

1997 ◽  
Vol 23 (5) ◽  
pp. 1075-1085 ◽  
Author(s):  
Andrea A. Milenbachs ◽  
David P. Brown ◽  
Marlena Moors ◽  
Philip Youngman
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Carbon Source ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals Influence of Sublethal Concentrations of Common Disinfectants on Expression of Virulence Genes in Listeria monocytogenes

2009 ◽  
Vol 76 (1) ◽  
pp. 303-309 ◽  
Author(s):  
Vicky G. Kastbjerg ◽  
Marianne Halberg Larsen ◽  
Lone Gram ◽  
Hanne Ingmer
Keyword(s):  
Gene Expression ◽  
Listeria Monocytogenes ◽  
Northern Blot ◽  
Food Industry ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Human Pathogen ◽  
Active Components ◽  
Virulence Gene Expression ◽  
Sublethal Concentrations

ABSTRACT Listeria monocytogenes is a food-borne human pathogen that causes listeriosis, a relatively rare infection with a high fatality rate. The regulation of virulence gene expression is influenced by several environmental factors, and the aim of the present study was to determine how disinfectants used routinely in the food industry affect the expression of different virulence genes in L. monocytogenes when added at sublethal concentrations. An agar-based assay was developed to screen the effect of disinfectants on virulence gene promoter expression and was validated at the transcriptional level by Northern blot analysis. Eleven disinfectants representing four different groups of active components were evaluated in this study. Disinfectants with the same active ingredients had a similar effect on gene expression. Peroxy and chlorine compounds reduced the expression of the virulence genes, and quaternary ammonium compounds (QAC) induced the expression of the virulence genes. In general, a disinfectant had similar effects on the expression of all four virulence genes examined. Northern blot analyses confirmed the downregulation of prfA and inlA expression by Incimaxx DES (a peroxy compound) and their upregulation by Triquart Super (a QAC) in L. monocytogenes EGD. Hence, sublethal concentrations of disinfectants routinely used in the food industry affect virulence gene expression in the human pathogen L. monocytogenes, and the effect depends on the active components of the disinfectant. From a practical perspective, the study underlines that disinfectants should be used at the lethal concentrations recommended by the manufacturers. Further studies are needed to elucidate whether the changes in virulence gene expression induced by the disinfectants have impact on virulence or other biological properties, such as antibiotic resistance.

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