Escherichia coli O157:H7 str. EDL933
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PROVIDER: PRJNA127423 | ENA |
REPOSITORIES: ENA
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Project description:Enterococcus faecalis downregulates virulence genes of EHEC
| PRJNA339823 | ENA
Project description:While significant advances have been made in EHEC pathogenesis, we still do not fully understand the impact of environmental stress on EHEC virulence. During the course of infection, EHEC must evade or overcome several biological barriers, the first of which is the gastric acidity encountered during passage through the stomach. EHEC is remarkable in its ability to tolerate this acidity. There are four different acid resistance systems that provide E. coli O157:H7 protection against exposure to low pH (2-2.5). Interestingly, EHEC uses these acid resistance systems differentially for survival in foods versus the bovine intestinal tract. The glutamate-dependent acid-resistance system is thought to offer the best protection below pH 3. Since the infectious dose of EHEC is so low (50-100 organisms), acid resistance becomes an important virulence trait. Studies of EHEC response to acid stress have focused primarily on levels of acid tolerance and the molecular basis of tolerance. However, the impact of acid stress on EHEC virulence is less well understood. In the related pathogen, EPEC, the plasmid-encoded regulator, Per, that regulates expression of many EPEC virulence factors, is regulated negatively at pH 5.5 and positively at pH 8.0, suggesting that virulence gene expression is repressed during mild acid stress and enhanced in alkaline pH typical of the small intestine. Expression of EPEC type III secreted factors involved in A/E lesion formation has been shown to be influenced by factors including culture media, iron and calcium levels. Protein secretion was inhibited at pH 6 and 8. In a third study, a gadE (encoding acid resistance regulator) mutation resulted in increased adhesion of E.coli O157:H7 to colonic epithelial cells, suggesting negative regulation of one or more adhesins. Other studies have reported that shiga toxin production is sensitive to culture conditions including pH. However, there are no studies of EHEC virulence changes after more severe acid stress nor studies linking stressed EHEC virulence phenotype with transcriptional changes. The goal of this study was to determine how acid stress affects EHEC virulence properties and through microarray analysis, define the genetic basis for these changes. Understanding how acid stress modulates the virulence potential of this pathogen is essential for delineating the pathogenesis of disease caused by EHEC infection and may offer novel approaches to prevent and treat EHEC infections.
2009-06-26 | GSE14069 | GEO
Project description:While significant advances have been made in EHEC pathogenesis, we still do not fully understand the impact of environmental stress on EHEC virulence. During the course of infection, EHEC must evade or overcome several biological barriers, the first of which is the gastric acidity encountered during passage through the stomach. EHEC is remarkable in its ability to tolerate this acidity. There are four different acid resistance systems that provide E. coli O157:H7 protection against exposure to low pH (2-2.5). Interestingly, EHEC uses these acid resistance systems differentially for survival in foods versus the bovine intestinal tract. The glutamate-dependent acid-resistance system is thought to offer the best protection below pH 3. Since the infectious dose of EHEC is so low (50-100 organisms), acid resistance becomes an important virulence trait. Studies of EHEC response to acid stress have focused primarily on levels of acid tolerance and the molecular basis of tolerance. However, the impact of acid stress on EHEC virulence is less well understood. In the related pathogen, EPEC, the plasmid-encoded regulator, Per, that regulates expression of many EPEC virulence factors, is regulated negatively at pH 5.5 and positively at pH 8.0, suggesting that virulence gene expression is repressed during mild acid stress and enhanced in alkaline pH typical of the small intestine. Expression of EPEC type III secreted factors involved in A/E lesion formation has been shown to be influenced by factors including culture media, iron and calcium levels. Protein secretion was inhibited at pH 6 and 8. In a third study, a gadE (encoding acid resistance regulator) mutation resulted in increased adhesion of E.coli O157:H7 to colonic epithelial cells, suggesting negative regulation of one or more adhesins. Other studies have reported that shiga toxin production is sensitive to culture conditions including pH. However, there are no studies of EHEC virulence changes after more severe acid stress nor studies linking stressed EHEC virulence phenotype with transcriptional changes. The goal of this study was to determine how acid stress affects EHEC virulence properties and through microarray analysis, define the genetic basis for these changes. Understanding how acid stress modulates the virulence potential of this pathogen is essential for delineating the pathogenesis of disease caused by EHEC infection and may offer novel approaches to prevent and treat EHEC infections. Bacteria were grown in LB broth overnight, then subcultured into DMEM and grown at 37C, 5%Co2. Bacteria were then subjected to one of three acid stress protocols: 1) UA30: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 30 minutes; 2) AA30: growth in DMEM pH 5.0 (adaptation) followed by growth in DMEM pH 3.0; 3) UA15: growth in DMEM pH 7.4 followed by growth in DMEM pH 3.0 for 15 minutes. DMEM was supplemented with 25 mM MES (pH 5.0) and in the case of the control (unadapted, unshocked) 25 mM MOPS (pH 7.4) and the adaptation step was again carried out at 37C and 5% CO2. Acid shocking was done at pH 3.0 (unbuffered) at room temperature for all treatments
2010-05-16 | E-GEOD-14069 | biostudies-arrayexpress
Project description:Enterohaemorrhagic E. coli (EHEC) is a significant human pathogens that cause outbreaks of haemorrhagic colitis and haemolytic uremic syndrome. During infection, pathogens compete for iron with the host, and one mechanism by which EHEC obtains iron is through haem uptake and utilitisation which is encoded by the chu operon. We have demonstrated that the haem receptor chuA is regulated by the Crp-cAMP-dependent sRNA CyaR. We further demonstrate that activation of chuA by CyaR is independent of the chuA RNA-thermometer and termination by Rho. These results highlight the ability of regulatory sRNAs to integrate multiple environmental signals into a layered hierarchy of signal input.
2022-03-03 | GSE197379 | GEO
Project description:In order to define the role of H-NS in regulating gene transcription and further find out the biological significance of this protein in EHEC, we conducted RNA-seq and then analyzed the transcriptome data, using EHEC O157:H7 strain EDL933 and Δhns. A total of 983 genes were found to be regulated by H-NS. 213 and 770 genes exhibited lower and higher transcript levels in Δhns than in WT, respectively. For instance, chemotaxis and flagellar associated genes were down-regulated in Δhns. Besides, 34 genes on virulence plasmid pO157 were down-regulated by H-NS. The outcome of RNA-seq were verified by real time quantitative PCR. As reported in Salmonella Typhimurium, Δhns showed a growth deficiency and altered fitness. We first detected that both stx1 and stx2 in EDL933 were repressed by H-NS. Although no survival difference between EDL933 and Δhns was detected when phagocytized by macrophage, we characterized the higher ability of colonization and in consequence the higher virulence of Δhns to BALB/c mice by experimental analyses than those of WT, especially when intact commensal flora of mice existed. This might indeed help us understand the core role of H-NS in depth.
2016-12-31 | GSE73969 | GEO
Project description:EHEC is a food-borne pathogen that colonizes human GI tract and leads to infection. To understand the process of colonization and to decipher if any factors secreted by intestinal epithelial cells help EHEC during the infection process, we studied expression of EHEC virulence gene expression when exposed to intestinal epithelial cell conditioned medium. In our study, we observed that exposure to epithelial cell conditioned medium for 1 h and 3 h increases expression of 32 out of 41 EHEC LEE virulence genes. In addition, expression of the shiga toxin 1 (Stx1) gene is up-regulated at 1 h of exposure. Also, 17 genes encoded by prophage 933W, including those for Stx2, are also upregulated at both time-points. The increase in 933W prophage expression is mirrored by a 2.7-fold increase in intracellular Stx2 phage titers. Consistent with the increase in virulence gene expression, we observed a 5-fold increase in EHEC attachment to epithelial cells when exposed to conditioned medium, suggesting that EHEC utilizes host cell molecules to increase virulence and infectivity. The molecule(s) responsible for increased EHEC virulence is heat-sensitive as heating the conditioned medium to 95oC abolishes the increase in attachment to epithelial cells. A similar decrease was observed when the conditioned medium was treated with proteinase-K to degrade the proteins. The secreted molecule(s) was found to be larger than 3 kDa and strongly suggests that the HCT-8 secreted molecule that increases EHEC virulence and colonization is a protein-based molecule. Affymetrix E. coli Genome 2.0 Arrays were used to determine the changes in EHEC virulence gene expression on exposure to intestinal epithelial cell-secreted factors (through growth in conditioned medium).
2012-10-04 | GSE22285 | GEO
Project description:Enterohemorrhagic Escherichia coli (EHEC), including serotype O157:H7, cause severe food-borne illness. On route to the human colon, they encounter and resist, numerous anti-microbial ingestion stresses. We hypothesize that these stresses cue EHEC to alter virulence properties. This study investigated the impact of bile salts on virulence properties and examined the genetic basis of the phenotypes. Established assays were used to examine adhesion to human epithelial cells, motility, verotoxin (VT) production and antimicrobial resistance with/without bile salt stress. Bacteria treated for 90 minute in DMEM plus 0.15% (w/v) bile salt mix demonstrated significantly enhanced adhesion to epithelial cells and resistance to several antibiotics but did not increase motility or VT production. To determine the genetic basis of these phenotypes a microarray experiment was conducted. EHEC strain 86-24, in mid-log phase of growth, were grown in DMEM pH 7.4 (control), or DMEM plus bile salt mix (0.15% w/v), for 90 minutes, statically at 37˚C, 5% CO2 prior to harvesting RNA for the microarray study. Four biological replicates were produced for each treatment. Microarray and gene expression analysis (semi-quantitative RT-PCR and beta-galactosidase reporter assays) of bile salt-treated EHEC revealed significant up-regulation of genes for lipid A modification, fimbriae, an efflux pump, and a two-component regulatory system relative to the bacteria grown in DMEM alone. This work points to several mechanisms that EHEC employs to resist the stresses of the human small intestine, notably efflux, antimicrobial resistance, and outer membrane alterations. Bile salts enhanced the virulence-related properties of increased adhesion and resistance to antimicrobials but not VT production or motility. This research contributes to our understanding of how EHEC senses and responds to host environmental signals and the mechanisms this pathogen uses to successfully colonize and infect the human host.
2011-09-06 | GSE22060 | GEO
Project description:RNA-seq to profile the H-NS transcriptome in EHEC O157:H7 strain EDL933
| PRJNA298626 | ENA
Project description:Escherichia coli O157:H7 is a food-borne pathogen that causes bloody diarrhea and hemolytic uremic syndrome. Hfq is an sRNA chaperone protein that is involved in post-transcriptional regulation of virulence genes in pathogenic bacteria. In EHEC strain EDL933, Hfq acts a negative regulator of the locus of enterocyte effacement (LEE) that encodes most of the proteins involved in type three secretion and attaching and effacing lesions. We deleted hfq in E. coli O157:H7 strain 86-24 and compared global transcription profiles of the hfq mutant to the wild type strain in exponential growth phase. Deletion of hfq affected transcription of genes common to nonpathogenic and pathogenic strains of E. coli as well as pathogen-specific genes. Downregulated genes in the hfq mutant included ler as well as genes encoded in LEE2-5 that encode for type three secretion and AE lesion formation. Decreased expression of the LEE genes in the hfq mutant occurred at mid-, late, and stationary growth phases in both LB and DMEM media as detected by qRT-PCR. We also confirmed decreased regulation of the LEE genes by examining secreted proteins and AE lesion formation by the hfq mutant and WT strains. Deletion of hfq also caused decreased expression of the two-component system qseBC involved in inter-kingdom signaling and virulence gene regulation in EHEC as well as an increase in stx2AB expression that encodes for the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a different regulatory role in EHEC 86-24 from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.
2012-01-06 | GSE30893 | GEO
Project description:EHEC is a food-borne pathogen that colonizes human GI tract and leads to infection. To understand the process of colonization and to decipher if any factors secreted by intestinal epithelial cells help EHEC during the infection process, we studied expression of EHEC virulence gene expression when exposed to intestinal epithelial cell conditioned medium. In our study, we observed that exposure to epithelial cell conditioned medium for 1 h and 3 h increases expression of 32 out of 41 EHEC LEE virulence genes. In addition, expression of the shiga toxin 1 (Stx1) gene is up-regulated at 1 h of exposure. Also, 17 genes encoded by prophage 933W, including those for Stx2, are also upregulated at both time-points. The increase in 933W prophage expression is mirrored by a 2.7-fold increase in intracellular Stx2 phage titers. Consistent with the increase in virulence gene expression, we observed a 5-fold increase in EHEC attachment to epithelial cells when exposed to conditioned medium, suggesting that EHEC utilizes host cell molecules to increase virulence and infectivity. The molecule(s) responsible for increased EHEC virulence is heat-sensitive as heating the conditioned medium to 95oC abolishes the increase in attachment to epithelial cells. A similar decrease was observed when the conditioned medium was treated with proteinase-K to degrade the proteins. The secreted molecule(s) was found to be larger than 3 kDa and strongly suggests that the HCT-8 secreted molecule that increases EHEC virulence and colonization is a protein-based molecule. Affymetrix E. coli Genome 2.0 Arrays were used to determine the changes in EHEC virulence gene expression on exposure to intestinal epithelial cell-secreted factors (through growth in conditioned medium). Overnight cultures of EHEC were diluted in LB medium to a turbidity of 0.1 at 600 nm. The cells were allowed to grow to a turbidity of 1.0 at 600 nm at 37°C and the EHEC cells were then resuspended in either fresh or conditioned medium. The cultures were then allowed to grow for 1 h or 3 h before cell pellets were collected by centrifugation and stored at -80°C. Total RNA was isolated from the cell pellets (173) and RNA quality was assessed using gel electrophoresis. Escherichia coli Genome 2.0 arrays (Affymetrix, Santa Clara, CA, USA) containing 10,208 probe sets for all 20,366 genes present in four strains of E. coli, including EHEC, were used to profile changes in gene expression using RNA samples for each treatment.
2012-10-04 | E-GEOD-22285 | biostudies-arrayexpress