scholarly journals The E. coli transcription factor GrlA is regulated by subcellular compartmentalization and activated in response to mechanical stimuli

2020 ◽  
Vol 117 (17) ◽  
pp. 9519-9528 ◽  
Author(s):  
Natalie Sirisaengtaksin ◽  
Max A. Odem ◽  
Rachel E. Bosserman ◽  
Erika M. Flores ◽  
Anne Marie Krachler
Keyword(s):  
Gastrointestinal Tract ◽  
Foodborne Pathogen ◽  
Virulence Gene ◽  
Adhesive Force ◽  
Mechanical Stimuli ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Sense And Respond ◽  
Subcellular Compartmentalization ◽  
Enterocyte Effacement

Enterohemorrhagic Escherichia coli (EHEC) is a foodborne pathogen that colonizes the gastrointestinal tract and has evolved intricate mechanisms to sense and respond to the host environment. Upon the sensation of chemical and physical cues specific to the host’s intestinal environment, locus of enterocyte effacement (LEE)-encoded virulence genes are activated and promote intestinal colonization. The LEE transcriptional activator GrlA mediates EHEC’s response to mechanical cues characteristic of the intestinal niche, including adhesive force that results from bacterial adherence to epithelial cells and fluid shear that results from intestinal motility and transit. GrlA expression and release from its inhibitor GrlR was not sufficient to induce virulence gene transcription; mechanical stimuli were required for GrlA activation. The exact mechanism of GrlA activation, however, remained unknown. We isolated GrlA mutants that activate LEE transcription, independent of applied mechanical stimuli. In nonstimulated EHEC, wild-type GrlA associates with cardiolipin membrane domains via a patch of basic C-terminal residues, and this membrane sequestration is disrupted in EHEC that expresses constitutively active GrlA mutants. GrlA transitions from an inactive, membrane-associated state and relocalizes to the cytoplasm in response to mechanical stimuli, allowing GrlA to bind and activate the LEE1 promoter. GrlA expression and its relocalization in response to mechanical stimuli are required for optimal virulence regulation and colonization of the host intestinal tract during infection. These data suggest a posttranslational regulatory mechanism of the mechanosensor GrlA, whereby virulence gene expression can be rapidly fine-tuned in response to the highly dynamic spatiotemporal mechanical profile of the gastrointestinal tract.

scholarly journals The Locus of Enterocyte Effacement (LEE)-Encoded Regulator Controls Expression of Both LEE- and Non-LEE-Encoded Virulence Factors in Enteropathogenic and EnterohemorrhagicEscherichia coli

2000 ◽  
Vol 68 (11) ◽  
pp. 6115-6126 ◽  
Author(s):  
Simon J. Elliott ◽  
Vanessa Sperandio ◽  
Jorge A. Girón ◽  
Sooan Shin ◽  
Jay L. Mellies ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Gene ◽  
Global Regulator ◽  
Lesion Formation ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Secretion Pathway ◽  
Regulatory Cascade ◽  
Enterocyte Effacement ◽  
Maximal Expression

ABSTRACT Regulation of virulence gene expression in enteropathogenicEscherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) is incompletely understood. In EPEC, the plasmid-encoded regulator Per is required for maximal expression of proteins encoded on the locus of enterocyte effacement (LEE), and a LEE-encoded regulator (Ler) is part of the Per-mediated regulatory cascade upregulating the LEE2, LEE3, andLEE4 promoters. We now report that Ler is essential for the expression of multiple LEE-located genes in both EPEC and EHEC, including those encoding the type III secretion pathway, the secreted Esp proteins, Tir, and intimin. Ler is therefore central to the process of attaching and effacing (AE) lesion formation. Ler also regulates the expression of LEE-located genes not required for AE-lesion formation, including rorf2, orf10,rorf10, orf19, and espF, indicating that Ler regulates additional virulence properties. In addition, Ler regulates the expression of proteins encoded outside the LEE that are not essential for AE lesion formation, including TagA in EHEC and EspC in EPEC. Δler mutants of both EPEC and EHEC show altered adherence to epithelial cells and express novel fimbriae. Ler is therefore a global regulator of virulence gene expression in EPEC and EHEC.

Glucose Decreases Virulence Gene Expression of Escherichia coli O157:H7

2012 ◽  
Vol 75 (4) ◽  
pp. 748-752 ◽  
Author(s):  
V. DELCENSERIE ◽  
G. LaPOINTE ◽  
T. CHARASLERTRANGSI ◽  
A. RABALSKI ◽  
M. W. GRIFFITHS
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Quorum Sensing ◽  
Shiga Toxin ◽  
Virulence Gene ◽  
Escherichia Coli O157 ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Reverse Transcription Pcr ◽  
Enterocyte Effacement

Escherichia coli O157:H7 is responsible for a human toxico-infection that can lead to severe complications such as hemolytic uremic syndrome. Inside the intestine, E. coli O157:H7 forms typical attaching-effacing lesions and produces Shiga toxins. The genes that are responsible for these lesions are located in a pathogenicity island called the locus of enterocyte effacement (LEE). LEE gene expression is influenced by quorum sensing through the luxS system. In this study, the effect of glucose on the expression of several genes from LEE, on the expression of Shiga toxin genes, and on the expression of luxS was assessed with real-time, reverse transcription PCR. All concentrations of glucose (from 0.1 to 1%) were able to down-regulate genes from the LEE operon. A slight down-regulation of genes implicated in Shiga toxin expression was also observed but was significant for low doses of glucose (0.1 to 0.5%) only. A slight but significant increase in luxS expression was observed with 1% glucose. This confirms that in addition to quorum sensing, the presence or absence of nutrients such as glucose has an impact on the down- or upregulation of LEE-encoded virulence genes by the bacterium. The influence of glucose on the virulence of E. coli O157:H7 has received little attention, and these results suggest that glucose can have an important effect on the virulence of E. coli O157:H7.

scholarly journals Salmonella typhimurium Encodes an SdiA Homolog, a Putative Quorum Sensor of the LuxR Family, That Regulates Genes on the Virulence Plasmid

1998 ◽  
Vol 180 (5) ◽  
pp. 1185-1193 ◽  
Author(s):  
Brian M. M. Ahmer ◽  
Jeroen van Reeuwijk ◽  
Cynthia D. Timmers ◽  
Peter J. Valentine ◽  
Fred Heffron
Keyword(s):  
Quorum Sensing ◽  
Salmonella Typhimurium ◽  
Virulence Gene ◽  
Gene Organization ◽  
Virulence Plasmid ◽  
Amino Acid Transporters ◽  
Gene Encoding ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Sense And Respond

ABSTRACT Quorum sensing is a phenomenon in which bacteria sense and respond to their own population density by releasing and sensing pheromones. In gram-negative bacteria, quorum sensing is often performed by the LuxR family of transcriptional regulators, which affect phenotypes as diverse as conjugation, bioluminescence, and virulence gene expression. The gene encoding one LuxR family member, named sdiA(suppressor of cell division inhibition), is present in theEscherichia coli genome. In this report, we have cloned theSalmonella typhimurium homolog of SdiA and performed a systematic screen for sdiA-regulated genes. A 4.4-kb fragment encoding the S. typhimurium sdiA gene was sequenced and found to encode the 3′ end of YecC (homologous to amino acid transporters of the ABC family), all of SdiA and SirA (Salmonella invasion regulator), and the 5′ end of UvrC. This gene organization is conserved between E. coli andS. typhimurium. We determined that the S. typhimurium sdiA gene was able to weakly complement the E. coli sdiA gene for activation of ftsQAZ at promoter 2 and for suppression of filamentation caused by an ftsZ(Ts) allele. To better understand the function of sdiA inS. typhimurium, we screened 10,000 random lacZYtranscriptional fusions (MudJ transposon mutations) for regulation bysdiA. Ten positively regulated fusions were isolated. Seven of the fusions were within an apparent operon containing ORF8, ORF9,rck (resistance to complement killing), and ORF11 of theS. typhimurium virulence plasmid. The three ORFs have now been named srgA, srgB, and srgC(for sdiA-regulated gene), respectively. The DNA sequence adjacent to the remaining three fusions shared no similarity with previously described genes.

scholarly journals Reconstitution of Acetosyringone-Mediated Agrobacterium tumefaciens Virulence Gene Expression in the Heterologous Host Escherichia coli

2001 ◽  
Vol 183 (12) ◽  
pp. 3704-3711 ◽  
Author(s):  
Scott M. Lohrke ◽  
Hongjiang Yang ◽  
Shouguang Jin
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Agrobacterium Tumefaciens ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Dependent Manner ◽  
Gene Encoding ◽  
Virulence Gene Expression ◽  
E Coli ◽  
Glucose Binding

ABSTRACT The ability to utilize Escherichia coli as a heterologous system in which to study the regulation ofAgrobacterium tumefaciens virulence genes and the mechanism of transfer DNA (T-DNA) transfer would provide an important tool to our understanding and manipulation of these processes. We have previously reported that the rpoA gene encoding the alpha subunit of RNA polymerase is required for the expression of lacZ gene under the control of virB promoter (virBp::lacZ) in E. colicontaining a constitutively active virG gene [virG(Con)]. Here we show that an RpoA hybrid containing the N-terminal 247 residues from E. coli and the C-terminal 89 residues from A. tumefaciens was able to significantly express virBp::lacZ in E. coli in a VirG(Con)-dependent manner. Utilization oflac promoter-driven virA and virGin combination with the A. tumefaciens rpoA construct resulted in significant inducer-mediated expression of thevirBp::lacZ fusion, and the level ofvirBp::lacZ expression was positively correlated to the copy number of the rpoA construct. This expression was dependent on VirA, VirG, temperature, and, to a lesser extent, pH, which is similar to what is observed in A. tumefaciens. Furthermore, the effect of sugars on virgene expression was observed only in the presence of thechvE gene, suggesting that the glucose-binding protein ofE. coli, a homologue of ChvE, does not interact with the VirA molecule. We also evaluated other phenolic compounds in induction assays and observed significant expression with syringealdehyde, a low level of expression with acetovanillone, and no expression with hydroxyacetophenone, similar to what occurs in A. tumefaciens strain A348 from which the virA clone was derived. These data support the notion that VirA directly senses the phenolic inducer. However, the overall level of expression of thevir genes in E. coli is less than what is observed in A. tumefaciens, suggesting that additional gene(s) from A. tumefaciens may be required for the full expression of virulence genes in E. coli.

scholarly journals H-NS Regulates DNA Repair inShigella

1998 ◽  
Vol 180 (19) ◽  
pp. 5260-5262 ◽  
Author(s):  
Sunil Palchaudhuri ◽  
Brandon Tominna ◽  
Myron A. Leon
Keyword(s):  
Dna Repair ◽  
Uv Irradiation ◽  
Shigella Flexneri ◽  
Virulence Gene ◽  
High Rate ◽  
High Survival ◽  
Virulence Gene Expression ◽  
E Coli ◽  
X Irradiation ◽  
K 12

ABSTRACT We report a new role for H-NS in Shigella spp.: suppression of repair of DNA damage after UV irradiation. H-NS-mediated suppression of virulence gene expression is thermoregulated inShigella, being functional at 30°C and nonfunctional at 37 to 40°C. We find that H-NS-mediated suppression of DNA repair after UV irradiation is also thermoregulated. Thus, Shigella flexneri M90T, incubated at 37 or 40°C postirradiation, shows up to 30-fold higher survival than when incubated at 30°C postirradiation. The hns mutants BS189 and BS208, both of which lack functional H-NS, show a high rate of survival (no repression) whether incubated at 30 or 40°C postirradiation. Suppression of DNA repair by H-NS is not mediated through genes on the invasion plasmid of S. flexneri M90T, since BS176, cured of plasmid, behaves identically to the parental M90T. Thus, inShigella the nonfunctionality of H-NS permits enhanced DNA repair at temperatures encountered in the human host. However, pathogenic Escherichia coli strains (enteroinvasive and enterohemorrhagic E. coli) show low survival whether incubated at 30 or 40°C postirradiation. E. coli K-12 shows markedly different behavior; high survival postirradiation at both 30 and 40°C. These K-12 strains were originally selected fromE. coli organisms subjected to both UV and X irradiation. Therefore, our data suggest that repair processes, extensively described for laboratory strains of E. coli, require experimental verification in pathogenic strains which were not adapted to irradiation.

scholarly journals Short Chain Fatty Acids Modulate the Growth and Virulence of Pathosymbiont Escherichia coli and Host Response

Antibiotics ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 462
Author(s):  
Shiying Zhang ◽  
Belgin Dogan ◽  
Cindy Guo ◽  
Deepali Herlekar ◽  
Katrina Stewart ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Virulence Gene ◽  
Short Chain Fatty Acids ◽  
Short Chain ◽  
Host Responses ◽  
Virulence Gene Expression ◽  
E Coli ◽  
The Impact ◽  
Chain Fatty Acids

Short chain fatty acids (SCFA), principally acetate, propionate, and butyrate, are produced by fermentation of dietary fibers by the gut microbiota. SCFA regulate the growth and virulence of enteric pathogens, such as enterohemorrhagic E. coli (EHEC), Klebsiella and Salmonella. We sought to investigate the impact of SCFA on growth and virulence of pathosymbiont E. coli associated with inflammatory bowel disease (IBD) and colorectal cancer (CRC), and their role in regulating host responses to bacterial infection in vitro. We found that under ileal conditions (pH = 7.4; 12 mM total SCFA), SCFA significantly (p < 0.05) potentiate the growth and motility of pathosymbiont E. coli. However, under colonic conditions (pH = 6.5; 65 to 123 mM total SCFA), SCFA significantly (p < 0.05) inhibit growth in a pH dependent fashion (up to 60%), and down-regulate virulence gene expression (e.g., fliC, fimH, htrA, chuA, pks). Functional analysis reveals that colonic SCFA significantly (p < 0.05) inhibit E. coli motility (up to 95%), infectivity (up to 60%), and type 1 fimbria-mediated agglutination (up to 50%). In addition, SCFA significantly (p < 0.05) inhibit the activation of NF-kB, and IL-8 production by epithelial cells. Our findings provide novel insights on the role of the regional chemical microenvironment in regulating the growth and virulence of pathosymbiont E. coli and opportunities for therapeutic intervention.

scholarly journals QseC inhibition as an antivirulence approach for colitis-associated bacteria

2016 ◽  
Vol 114 (1) ◽  
pp. 142-147 ◽  
Author(s):  
Michelle G. Rooks ◽  
Patrick Veiga ◽  
Analise Z. Reeves ◽  
Sydney Lavoie ◽  
Koji Yasuda ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Intestinal Inflammation ◽  
Virulence Gene ◽  
Susceptible Host ◽  
Virulence Gene Expression ◽  
Bacterial Signaling ◽  
Two Component ◽  
Sense And Respond

Hosts and their microbes have established a sophisticated communication system over many millennia. Within mammalian hosts, this dynamic cross-talk is essential for maintaining intestinal homeostasis. In a genetically susceptible host, dysbiosis of the gut microbiome and dysregulated immune responses are central to the development of inflammatory bowel disease (IBD). Previous surveys of stool from theT-bet−/−Rag2−/−IBD mouse model revealed microbial features that discriminate between health and disease states. Enterobacteriaceae expansion and increased gene abundances for benzoate degradation, two-component systems, and bacterial motility proteins pointed to the potential involvement of a catecholamine-mediated bacterial signaling axis in colitis pathogenesis. Enterobacteriaceae sense and respond to microbiota-generated signals and host-derived catecholamines through the two-component quorum-sensingEscherichia coliregulators B and C (QseBC) system. On signal detection, QseC activates a cascade to induce virulence gene expression. Although a single pathogen has not been identified as a causative agent in IBD, adherent-invasiveEscherichia coli(AIEC) have been implicated. Flagellar expression is necessary for the IBD-associated AIEC strain LF82 to establish colonization. Thus, we hypothesized thatqseCinactivation could reduce LF82’s virulence, and found that an absence ofqseCleads to down-regulated flagellar expression and motility in vitro and reduced colonization in vivo. We extend these findings on the potential of QseC-based IBD therapeutics to three preclinical IBD models, wherein we observe that QseC blockade can effectively modulate colitogenic microbiotas to reduce intestinal inflammation. Collectively, our data support a role for QseC-mediated bacterial signaling in IBD pathogenesis and indicate that QseC inhibition may be a useful microbiota-targeted approach for disease management.

scholarly journals Prevalence and Virulence Gene Profiles of Escherichia coli O157 from Cattle Slaughtered in Buea, Cameroon

2020 ◽  
Author(s):  
Elvis Achondou Akomoneh ◽  
Seraphine Nkie Esemu ◽  
Achah Jerome Kfusi ◽  
Roland N. Ndip ◽  
Lucy M. Ndip
Keyword(s):  
Escherichia Coli ◽  
Virulence Genes ◽  
Foodborne Pathogen ◽  
Virulence Gene ◽  
Latex Agglutination ◽  
Health Concern ◽  
E Coli ◽  
Uremic Syndrome ◽  
Human Infections ◽  
Pcr Targeting

ABSTRACTBackgroundEscherichia coli O157 is an emerging foodborne pathogen of great public health concern. It has been associated with bloody diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome in humans. Most human infections have been traced to cattle and the consumption of contaminated cattle products. In order to understand the risk associated with the consumption of cattle products, this study sought to investigate the prevalence and identify virulence genes in E. coli O157 from cattle in Cameroon.MethodA total of 512 rectal samples were obtained and analysed using conventional bacteriological methods (enrichment on modified Tryptone Soy Broth and selective plating on Cefixime-Tellurite Sorbitol Mac-Conkey Agar) for the isolation of E. coli O157. Presumptive E. coli O157 isolates were confirmed serologically using E. COLIPRO™ O157 latex agglutination test and molecularly using PCR targeting the rfb gene in the isolates. Characterisation of the confirmed E. coli O157 strains was done by amplification of stx1, stx2, eaeA and hlyA virulence genes using both singleplex and multiplex PCR.ResultsE. coli O157 was detected in 56 (10.9%) of the 512 samples examined. The presence of the virulence genes stx2, eaeA and hylA was demonstrated in 96.4% (54/56) of the isolates and stx1 in 40 (71.4%) of the 54. The isolates exhibited three genetic profiles (I-III) with I (stx1, stx2, eaeA and hlyA) being the most prevalent (40/56; 71.4%) while two isolates had none of the virulence genes tested.ConclusionA proportion of cattle slaughtered in abattoirs in Buea are infected with pathogenic E. coli O157 and could be a potential source of human infections. We recommend proper animal food processing measures and proper hygiene be prescribed and implemented to reduce the risk of beef contamination.

scholarly journals Multiple evolutionary trajectories for non-O157 Shiga toxigenic Escherichia coli

2019 ◽  
Author(s):  
Nabil-Fareed Alikhan ◽  
Nathan L. Bachmann ◽  
Nouri L. Ben Zakour ◽  
Nicola K. Petty ◽  
Mitchell Stanton-Cook ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Virulence Gene ◽  
Human Infection ◽  
Phylogenomic Analysis ◽  
E Coli ◽  
O Antigen ◽  
Food Borne Illness ◽  
Uremic Syndrome ◽  
Enterocyte Effacement ◽  
Genomic Regions

AbstractBackgroundShiga toxigenic Escherichia coli (STEC) is an emerging global pathogen and remains a major cause of food-borne illness with more severe symptoms including hemorrhagic colitis and hemolytic-uremic syndrome. Since the characterization of the archetypal STEC serotype, E. coli O157:H7, more than 250 STEC serotypes have been defined. Many of these non-O157 STEC are associated with clinical cases of equal severity as O157. In this study, we utilize whole genome sequencing of 44 STEC strains from eight serogroups associated with human infection to establish their evolutionary relationships and contrast this with their virulence gene profiles and established typing methods.ResultsOur phylogenomic analysis delineated these STEC strains into seven distinct lineages, each with a characteristic repertoire of virulence factors. Some lineages included commensal or other E. coli pathotypes. Multiple independent acquisitions of the Locus for Enterocyte Effacement were identified, each associated with a distinct repertoire of effector genes. Lineages were inconsistent with O-antigen typing in several instances, consistent with lateral gene transfer within the O-antigen locus. STEC lineages could be defined by the conservation of clustered regularly interspaced short palindromic repeats (CRISPRs), however, no CRISPR profile could differentiate STEC from other E. coli strains. Six genomic regions (ranging from 500 bp - 10 kbp) were found to be conserved across all STEC in this dataset and may dictate interactions with Stx phage lysogeny.ConclusionsThe genomic analyses reported here present non-O157 STEC as a diverse group of pathogenic E. coli emerging from multiple lineages that independently acquired mobile genetic elements that promote pathogenesis.

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