Genome-wide transcriptional profiling of the cell envelope stress response of Listeria monocytogenes
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ABSTRACT:
ORGANISM(S): Listeria monocytogenes Listeria monocytogenes EGD-e
PROVIDER: GSE32913 | GEO | 2012/01/24
SECONDARY ACCESSION(S): PRJNA146541
REPOSITORIES: GEO
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Project description:The Gram-positive bacterium Listeria monocytogenes is widely distributed in the environment and capable of causing food-borne infections in susceptible individuals. In this study, we investigated the cell envelope stress response in L. monocytogenes. Whole-genome transcriptional profiling was performed to investigate the response upon exposure to the cell wall antibiotic cefuroxime. Differential expression (≥ 2-fold difference) of 558 genes was observed, corresponding to 20% of the L. monocytogenes genome. The majority of genes strongly induced by cefuroxime exposure have cell envelope-related functions, including the dlt-operon, genes encoding penicillin-binding proteins, and members from the LiaRS regulon. The virulence-associated genes dacA and lmo2714 were up-regulated upon cefuroxime exposure, whereas PrfA-regulated virulence genes, required for invasion and intracellular replication, were repressed. A large overlap was observed between the cefuroxime stimulon and genes known to be induced in L. monocytogenes in blood and during intracellular infection, indicating that the cell envelope stress response is active at various stages of the infectious process. Genes involved in stress tolerance (htrA, ctc) and signal transduction (lisRK) were also found among the highly up-regulated genes. We analysed the roles of the two-component systems LisRK and CesRK, showing that activation of the most highly cefuroxime-induced genes was LisR- and CesR-dependent. Using genetic analyses, we showed that several genes of the cefuroxime stimulon contribute to the innate resistance of L. monocytogenes to cefuroxime and tolerance to other cell envelope-perturbing conditions. Collectively, these findings demonstrate central roles for LisRK and CesRK in orchestrating the cell envelope stress response in L. monocytogenes. Cefuroxime induced expression was measured in the wildtype, lisR deletion mutant and, cesR deletion mutant after 60 minutes of exposure and compared to unexposed control samples. Multiple technical and biological replicates where analyzed with or without the dyes-swapped.
2012-01-24 | E-GEOD-32913 | biostudies-arrayexpress
Project description:Information regarding the Alkaline Tolerance Response (AlTR) in Listeria monocytogenes is very limited. In this study, L. monocytogenes was shown to exhibit a significant adaptive alkaline tolerance response (AlTR) following a 1-h exposure to mild alkaline (pH 9.5), which is capable of protecting cells from subsequent lethal alkali stress (pH 12.0). Treatment of adapted cells with protein synthesis inhibitor chloramphenicol has revealed that AlTR is at least partially protein-dependent. In order to gain a more comprehensive perspective on the physiology and regulation of AlTR, we compared differential gene expression and protein content at pH 9.5 using microarray and two-dimensional (2D) gel electrophoresis, (combined with mass spectrometry) respectively. By interfacing the results of both approaches this study showed strong evidence that alkali tolerance response in L. monocytogenes functions as to minimize excess alkalisation and energy expenditures while mobilizing available carbon sources. Adaptive intracellular gene expression involved genes that are associated with virulence, the general stress response, cell division, and changes in cell wall structure and included many genes with unknown functions. The variability observed between results of cDNA arrays and 2D may account for posttranslational modifications. Interestingly, several alkali induced genes/proteins can provide a cross protective overlap to other types of stresses. Alkaline pH provides therefore L. monocytogenes with nonspecific multiple-stress resistance that may be vital for survival in the human gastrointestinal tract as well as within food processing systems where similar alkaline conditions as the ones used in this study prevail. Keywords: Transcriptomic and Proteomic Comparison Study
2007-07-25 | GSE7966 | GEO
Project description:Listeria monocytogenes is a gram-positive, food-borne pathogen responsible for invasive infections with high overall mortality. Early host defenses encountered by L. monocytogenes following ingestion include low pH of the stomach and bile present in the small intestinal lumen. We hypothesized that “epidemic” strains are better able to withstand exposure to low pH and bile encountered in the gastrointestinal tract as compared to most “environmental” strains. Furthermore, we hypothesized that epidemic and environmental strains would have distinct transcriptional programs upon exposure to these conditions. Our treatments included 1 hr exposure to acid (pH 5.5 and 3.5) and bile (0.3%) stress. Strains were pre-exposed to pH 5.5 (1 hr) before being treated with pH 3.5. We used a collection of 12 previously characterized epidemic and environmental strains and each strainXtreatment combination included 3 biological replicates for each microarray experiment. All microarray experiments were two color competitive hybridizations that paired experimental conditions with the same strain at neutral pH for acid stress and pH 5.5 for bile stress. Transcriptomes of environmental strains exposed to acid and bile stress showed remarkably greater number of genes with differences of ≥2-fold expression levels as compared to epidemic strains (5 and 7, respectively). Environmental strains were characterized by up-regulation of several stress related genes and down-regulation of several cell envelope biosynthesis and virulence related genes, suggesting that complex regulatory networks orchestrate the cellular changes in the environmental strains to overcome stressful environments. The transcriptome of epidemic strains, in contrast, showed muted responses to these stress conditions implying their pre-adaptability to acid and bile stress encountered during natural infection that may enable epidemic strains to survive and become “primed” for subsequent colonization and infection in the lower gastrointestinal tract. Keywords: stress response, comparative transcriptomics, acid-adaptation, differential virulence, acid-stress response, bile-stress response
2009-06-15 | GSE10603 | GEO
Project description:Listeria monocytogenes strains classify into at least three distinct phylogenetic lineages. Correlations exist between lineage classification and source of bacterial isolation, e.g., human clinical and food isolates usually classify into either lineage I or II, however, human clinical isolates are over-represented in lineage I while food isolates are over-represented in lineage II. σB, a transcriptional regulator previously demonstrated to contribute to environmental stress response and virulence in L. monocytogenes lineage II strains, was hypothesized to provide differential capabilities for L. monocytogenes survival in various niches (e.g., food vs. human clinical). To determine if σB contributions to stress response and virulence differ across diverse L. monocytogenes strains, ΔsigB mutations were created in strains from lineages I, II, IIIA, and IIIB. Paired parent and ΔsigB mutant strains were tested for acid and oxidative stress survival, Caco-2 cell invasion efficiency, and virulence using the guinea pig listeriosis infection model. Parent and ΔsigB mutant strain transcriptomes were compared using whole-genome expression microarrays. σB contributed to virulence in each strain. However, while σB contributed significantly to acid and oxidative stress survival and Caco-2 cell invasion in lineage I, II, and IIIB strains, σB contributions were not significant for these phenotypes in the lineage IIIA strain. A core set of 63 genes was positively regulated by σB in all four strains; different total numbers of genes were positively regulated by σB in each strain. Our results suggest that σB universally contributes to L. monocytogenes virulence, but specific σB-regulated stress response phenotypes vary among strains.
2010-06-01 | E-GEOD-21427 | biostudies-arrayexpress
Project description:Listeria monocytogenes strains classify into at least three distinct phylogenetic lineages. Correlations exist between lineage classification and source of bacterial isolation, e.g., human clinical and food isolates usually classify into either lineage I or II, however, human clinical isolates are over-represented in lineage I while food isolates are over-represented in lineage II. σB, a transcriptional regulator previously demonstrated to contribute to environmental stress response and virulence in L. monocytogenes lineage II strains, was hypothesized to provide differential capabilities for L. monocytogenes survival in various niches (e.g., food vs. human clinical). To determine if σB contributions to stress response and virulence differ across diverse L. monocytogenes strains, ΔsigB mutations were created in strains from lineages I, II, IIIA, and IIIB. Paired parent and ΔsigB mutant strains were tested for acid and oxidative stress survival, Caco-2 cell invasion efficiency, and virulence using the guinea pig listeriosis infection model. Parent and ΔsigB mutant strain transcriptomes were compared using whole-genome expression microarrays. σB contributed to virulence in each strain. However, while σB contributed significantly to acid and oxidative stress survival and Caco-2 cell invasion in lineage I, II, and IIIB strains, σB contributions were not significant for these phenotypes in the lineage IIIA strain. A core set of 63 genes was positively regulated by σB in all four strains; different total numbers of genes were positively regulated by σB in each strain. Our results suggest that σB universally contributes to L. monocytogenes virulence, but specific σB-regulated stress response phenotypes vary among strains.
2010-06-01 | GSE21427 | GEO
Project description:Listeria monocytogenes SigB and PrfA are pleiotropic regulators of stress response and virulence gene expression, which have been shown to co-regulate genes in L. monocytogenes. We performed whole genome transcriptional profiling in the presence of PrfA* and active SigB, to identify the overlaps between the PrfA virulence regulon and the SigB stress response regulon. In L. monocytogenes, the PrfA* allele contributes to the activation of virulence genes to a level comparable to that of intracellular growing L. monocytogenes. Our results showed that the core PrfA regulon consists of 12 genes previously described as PrfA regulated. Furthermore, we found that the role of SigB during virulence gene regulation changes, dependent on the presence or absence of PrfA*. In the absence of PrfA*, SigB activated the transcription of virulence genes such as inlA and inlB. In the presence of PrfA*, SigB negatively influenced the transcription of genes in the PrfA core regulon. The observed effect of SigB on the transcript level of PrfA regulated genes was shown to reduce the cytotoxic effect of the PrfA* allele in HepG-2 cells. Our results indicate that the SigB-PrfA regulatory network is important for the adjustment of virulence gene transcription to ensure L. monocytogenes success as an intracellular pathogen. Keywords: comparison of gene expression of regulatory mutants
2008-10-01 | GSE11347 | GEO
Project description:In several gram-positive bacterial genera including Bacillus, Staphylococcus, and Listeria, sigma B (σB) has been identified as a stress-responsive alternative sigma factor responsible for initiating transcription of genes (the σB regulon) involved in response to stress-inducing environmental conditions. In L. monocytogenes, a foodborne pathogen of considerable threat to public health and the food industry, σB is involved in regulation of stress response and virulence gene expression. We have defined the σB regulon in L. monocytogenes during early stationary phase and under salt stress (0.3M NaCl) conditions using whole-genome microarrays, identifying 168 genes that generated ≥2.0-fold higher signals in the parental strain 10403S than in an isogenic sigB null mutant (ΔsigB), categorized into nine functional groups including stress-response genes (12), virulence genes (5), and genes related to transport (26) and metabolism (45). To gain a broader biological perspective of the σB stress response system, we applied these microarrays to Listeria innocua under the same environmental conditions. Our studies revealed 64 candidates in the L. innocua σB regulon with ≥2.0-fold higher signals in the parent than in a ΔsigB mutant; 49 of the 64 genes overlap with the L. monocytogenes σB regulon, indicating extensive overlap in σB-controlled genes between the two species. Further transcriptional analysis using TaqMan quantitative real time RT-PCR was performed for selected genes that displayed contrasting fold changes among the four microarray data sets (two stress conditions per species). We report novel members of the L. monocytogenes σB regulon, as well as the initial definition of the L. innocua σB regulon. Our comparative studies of the σB stress response systems in L. monocytogenes and L. innocua revealed features of the σB regulon that are conserved and unique to the two species. Keywords: Listeria monocytogenes, Listeria innocua, SigB regulon, salt stress, stationary phase
2007-11-29 | GSE7492 | GEO
Project description:Listeria monocytogenes SigB and PrfA are pleiotropic regulators of stress response and virulence gene expression, which have been shown to co-regulate genes in L. monocytogenes. We performed whole genome transcriptional profiling in the presence of PrfA* and active SigB, to identify the overlaps between the PrfA virulence regulon and the SigB stress response regulon. In L. monocytogenes, the PrfA* allele contributes to the activation of virulence genes to a level comparable to that of intracellular growing L. monocytogenes. Our results showed that the core PrfA regulon consists of 12 genes previously described as PrfA regulated. Furthermore, we found that the role of SigB during virulence gene regulation changes, dependent on the presence or absence of PrfA*. In the absence of PrfA*, SigB activated the transcription of virulence genes such as inlA and inlB. In the presence of PrfA*, SigB negatively influenced the transcription of genes in the PrfA core regulon. The observed effect of SigB on the transcript level of PrfA regulated genes was shown to reduce the cytotoxic effect of the PrfA* allele in HepG-2 cells. Our results indicate that the SigB-PrfA regulatory network is important for the adjustment of virulence gene transcription to ensure L. monocytogenes success as an intracellular pathogen. Keywords: comparison of gene expression of regulatory mutants The experimental design included 4 mutant strains of L. monocytogenes 10403S (PrfA*, delta prfA, delta prfA delta sigB, and PrfA* delta sigB), of which cDNA generated from 4 biological replicates were hybridized in all possible pairwise comparisons. Data were analyzed using a one way ANOVA in R/MAANOVA to determine significant differences in gene expression among the different strains. A two way ANOVA implemented in R/MAANOVA determined significant differences in gene expression due to the presence or absence of SigB and PrfA.
2010-05-19 | E-GEOD-11347 | biostudies-arrayexpress
Project description:Genome-wide transcriptional profiling of the cell envelope stress response of Listeria monocytogenes
| PRJNA146541 | ENA
Project description:Campylobacter jejuni is a prevalent cause of bacterial gastroenteritis in humans worldwide. The mechanism by which C. jejuni survives stomach acidity remains unknown. Herein, we have demonstrated that C. jejuni with a fur deletion was more sensitive to acid than the wild-type strain. Profiling the acid stimulon of the C. jejuni ∆fur mutant allowed us to uncover Fur-regulated genes under acidic conditions. The up-regulation of heat shock genes and the down-regulation of genes involved in flagellar and cell envelope biogenesis in the fur mutant highlight the importance of Fur in Campylobacter acid survival. Interestingly, prior acid exposure of C. jejuni cross-protected the bacterium against oxidative stress. Western-blot analysis and real-time qRT-PCR revealed an increased expression of the catalase KatA in acid-stressed C. jejuni relative to unstressed bacteria. The enhanced survival of C. jejuni to oxidative stress was shown to be Fur-dependent through the regulation of katA expression. Electrophoretic mobility shift assay (EMSA) demonstrated that the binding affinity between Fur and katA is reduced under low pH allowing for higher expression of katA and the defense against oxidative stress. Strikingly, the ∆fur mutant exhibited a reduced virulence capacity in both human epithelial cells and G. mellonella infection model as compared to C. jejuni wild-type. Altogether, this is the first study showing that in addition to its role in iron metabolism, Fur is an important regulator of C. jejuni acid response and cross-protection against other stresses. Moreover, our results clearly demonstrate that Fur plays a substantial role in C. jejuni host pathogenesis. Campylobacter jejuni is a prevalent cause of bacterial gastroenteritis in humans worldwide. The mechanism by which C. jejuni survives stomach acidity remains unknown. Herein, we have demonstrated that C. jejuni with a fur deletion was more sensitive to acid than the wild-type strain. Profiling the acid stimulon of the C. jejuni ∆fur mutant allowed us to uncover Fur-regulated genes under acidic conditions. The up-regulation of heat shock genes and the down-regulation of genes involved in flagellar and cell envelope biogenesis in the fur mutant highlight the importance of Fur in Campylobacter acid survival. Interestingly, prior acid exposure of C. jejuni cross-protected the bacterium against oxidative stress. Western-blot analysis and real-time qRT-PCR revealed an increased expression of the catalase KatA in acid-stressed C. jejuni relative to unstressed bacteria. The enhanced survival of C. jejuni to oxidative stress was shown to be Fur-dependent through the regulation of katA expression. Electrophoretic mobility shift assay (EMSA) demonstrated that the binding affinity between Fur and katA is reduced under low pH allowing for higher expression of katA and the defense against oxidative stress. Strikingly, the ∆fur mutant exhibited a reduced virulence capacity in both human epithelial cells and G. mellonella infection model as compared to C. jejuni wild-type. Altogether, this is the first study showing that in addition to its role in iron metabolism, Fur is an important regulator of C. jejuni acid response and cross-protection against other stresses. Moreover, our results clearly demonstrate that Fur plays a substantial role in C. jejuni host pathogenesis.
2016-03-17 | GSE73796 | GEO