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  • 1
    Electronic Resource
    Electronic Resource
    Effects of DNase production, plasmid size, and restriction barriers on transformation of Vibrio cholerae by electroporation and osmotic shock (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 68 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Attempts to transform wilt type strains of V. cholerae with plasmid DNA by traditional osmotic shock methods were note successful. A mutant of V. cholerae that was deficient in extracellular DNase was transformed with plasmid DNA by osmotic shock, demonstrating directly that extracellular DNase is a major barrier to transformation of V. cholerae. Transformation of wild type of DNase-negative strains of V. cholerae was accomplished by electroporation. Efficiency of transformation by electroporation increased with field strength, decreased with plasmid size, and was relatively insensitive to changes in the electrolyte composition of the buffer as long as isotonic sucrose was present. Host-controlled modification/restriction systems also affected transformation efficiency in V. cholerae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb04139.x
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative analysis of the hemolysin genes of Vibrio cholerae non-01, V. mimicus, and V. hollisae that are similar to the tdh gene of V. parahaemolyticus (1990)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 67 (1990), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The genes encoding the hemolysis similar to the thermostable direct hemolysin (tdh gene) of Vibrio parahaemolyticus were cloned from chromosomes of V. mimicus and V. hollisae. These cloned hemolysin genes and previously cloned tdh genes of V. parahaemolyticus and V. cholerae non-01 were compared by physical mapping and by hybridization with oligodeoxyribonucleotide probes. The nucleotide sequences in the coding regions of all the cloned hemolysin genes were very homologous and had only minor variations but the sequences flanking the homolysin genes were dissimilar, indicating that the hemolysin genes have a common ancestor and suggesting that they may have been transferred between Vibrio species as a descrete unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1990.tb04028.x
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  • 3
    Electronic Resource
    Electronic Resource
    EspB and EspD require a specific chaperone for proper secretion from enteropathogenic Escherichia coli (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 27 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enteropathogenic Escherichia coli uses a type III secretion apparatus to deliver proteins essential for pathogenesis to the host epithelium. Several proteins have been detected in culture supernatants of the prototype EPEC strain E2348/69 and three of these, EspA, EspB, and EspD, use type III machinery for export. Here, we report the identification and characterization of CesD, a protein required for proper EspB and EspD secretion. CesD shows sequence homology to chaperone proteins from other type III secretion pathways. Based on this, we hypothesize that CesD may function as a secretion chaperone in EPEC. A mutation in cesD abolished EspD secretion into culture supernatants and reduced the amount of secreted EspB, but had little effect on the amount of secreted EspA. The mutant strain was negative for both FAS and Tir phosphorylation, consistent with the previously described roles for EspB and EspD in EPEC pathogenesis. CesD was shown to interact with EspD but not EspB or EspA. CesD was detected in the bacterial cytosol, and, surprisingly, a substantial amount of the protein was also found to be associated with the inner membrane. Thus, although CesD has some attributes that are similar to other type III secretion chaperones, its membrane localization separates it from previously described members of this family.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00771.x
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of ToxR-dependent transcription activation of ompU, the gene encoding a major envelope protein in Vibrio cholerae (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 29 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The membrane proteins ToxR and ToxS regulate a variety of genes associated with the virulence of Vibrio cholerae, the agent of human cholera. One of the ToxRS-regulated genes is the ompU gene, which encodes a porin that may also act as an adhesin. To begin to understand the mechanism of ompU transcription activation by ToxRS, we performed genetic and biochemical studies on the ompU promoter. Deletions with a 5′ end-point at or downstream of −128, relative to the start site for transcription, did not direct expression of a lacZ reporter gene in wild-type V. cholerae, although the −128 promoter fragment did direct ToxRS-dependent reporter gene activity under conditions of ToxR overexpression in E. coli. Consistent with the activation data is that membranes containing ToxR and ToxS caused a gel electrophoretic mobility shift when mixed at low concentrations with deletion fragments whose end-point is at −211, but not with −128 or −68 fragments. ToxRS membranes did shift the −128 fragment when added at higher concentrations. DNase I footprinting analysis of ompU promoter DNA complexed with ToxRS membranes demonstrated protection of three sites: an upstream site ranging from −238 to −139, and two downstream sites ranging from −116 to −58 and −53 to −24. Within the DNA protected from DNase I digestion by ToxRS membranes, there are no elements bearing similarity to those identified previously within the promoters of two other ToxR-dependent genes, ctxA and toxT. We suggest a model for transcription activation that involves sequential ToxR-binding events to distinct regions in the ompU promoter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00925.x
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular cloning and transcriptional regulation of ompT, a ToxR-repressed gene in Vibrio cholerae (2000)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In pathogenic Vibrio cholerae, at least 17 genes are co-ordinately regulated by ToxR. Most of these genes, including those that encode cholera toxin (CT), toxin co-regulated pilus (TCP), accessory colonization factor (ACF) and OmpU, are positively regulated. OmpT is the only identified protein under negative regulation of ToxR. To understand the molecular mechanism by which ToxR represses OmpT expression, we cloned ompT and characterized the ompT promoter and its interaction with ToxR. Sequence analysis revealed that ompT encodes a predicted 35.8 kDa outer membrane porin of V. cholerae. Primer extension analysis identified a transcriptional start site 104 bp upstream of the translational start codon. Both primer extension analysis and promoter fusion studies showed that ToxR represses OmpT expression at the transcriptional level. Promoter fusion studies also suggest that cyclic AMP receptor protein (CRP) is involved in ompT activation. Gel mobility shift assays combined with DNase I footprinting analysis demonstrated that ToxR mediates repression of ompT transcription by directly binding to an A/T-rich region between −95 and −30 of the ompT promoter. To further understand how the interaction of ToxR with different promoters results in its function as an activator or repressor, we have also mapped the regions on the ctxAB and toxT promoters to which ToxR binds. The regions protected by ToxR on each of these promoters are all A/T rich and large in size, although they are positioned differently relative to each transcriptional start site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.01699.x
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  • 6
    Electronic Resource
    Electronic Resource
    A cloned pathogenicity island from enteropathogenic Escherichia coli confers the attaching and effacing phenotype on E. coli K-12 (1997)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 23 (1997), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Attaching and effacing (AE) bacteria are a diverse group of gastrointestinal pathogens, comprising members of four genera, that cause the intestinal epithelial microvilli to be replaced with raised clusters of filamentous actin that conform to the surface of attached bacteria. We have cloned a 35.4 kb ‘pathogenicity island’ from the prototype AE bacterium, enteropathogenic Escherichia coli, containing all previously described AE genes. Transfer of this pathogenicity island to avirulent E. coli converts the recipients into strains that secrete virulence proteins, induce host signal-transduction pathways, and cause AE lesions on cultured epithelial cells. These results demonstrate that this pathogenicity island contains all pathogen-specific genes necessary for inducing AE lesions, and that the defining feature of this class of pathogens can be acquired by an avirulent bacterium in a single genetic step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1997.2311591.x
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  • 7
    Electronic Resource
    Electronic Resource
    The complete sequence of the locus of enterocyte effacement (LEE) from enteropathogenic Escherichia coli E2348/69 (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00783.x
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the second long polar (LP) fimbriae of Escherichia coli O157:H7 and distribution of LP fimbriae in other pathogenic E. coli strains (2004)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 238 (2004), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A second region containing five genes homologous to the long polar fimbrial operon of Salmonella enterica serovar Typhimurium is located in the chromosome of enterohemorrhagic Escherichia coli (EHEC) O157:H7. A non-fimbriated E. coli K-12 strain carrying the cloned EHEC lpf (lpf2) genes expressed thin fibrillae-like structures on its surface and displayed reduced adherence to tissue culture cells. Neither mutation in the lpfA2 gene in either the parent or lpfA1 mutant strains showed an effect in adherence or in the formation of A/E lesions on HeLa cells. lpfA2 isogenic mutant strains adhere to Caco-2 cells almost as well as the wild-type at 5 h, but they were deficient in adherence at early time points. A collection of diarrheagenic E. coli strains were investigated for the presence of lpfA1 and lpfA2 and results showed that these genes are present in specific serogroups which are phylogenetically related. Our results suggest that LP fimbriae 2 may contribute to the early stages of EHEC adhesion and that genes encoding the major LP fimbrial subunits are present in a small group of EHEC and EPEC serotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.2004.tb09774.x
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  • 9
    Electronic Resource
    Electronic Resource
    StcE, a metalloprotease secreted by Escherichia coli O157:H7, specifically cleaves C1 esterase inhibitor (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Escherichia coli O157:H7 causes diarrhoea, haemorrhagic colitis, and the haemolytic uraemic syndrome. We have identified a protein of previously unknown function encoded on the pO157 virulence plasmid of E. coli O157:H7, which is the first described protease that specifically cleaves C1 esterase inhibitor (C1-INH), a member of the serine protease inhibitor family. The protein, named StcE for secreted protease of C1 esterase inhibitor from EHEC (formerly Tagn), cleaves C1-INH to produce (unique) ≈ 60–65 kDa fragments. StcE does not digest other serine protease inhibitors, extracellular matrix proteins or universal protease targets. We also observed that StcE causes the aggregation of cultured human T cells but not macrophage-like cells or B cells. Substitution of aspartic acid for glutamic acid at StcE position 435 within the consensus metalloprotease active site ablates its abilities to digest C1-INH and to aggregate T cells. StcE is secreted by the etp type II secretion pathway encoded on pO157, and extracellular StcE levels are positively regulated by the LEE-encoded regulator, Ler. StcE antigen and activity were detected in the faeces of a child with an E. coli O157:H7 infection, demonstrating the expression of StcE during human disease. Cleavage of C1-INH by StcE could plausibly cause localized pro-inflammatory and coagulation responses resulting in tissue damage, intestinal oedema and thrombotic abnormalities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02997.x
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  • 10
    Electronic Resource
    Electronic Resource
    ToxR interferes with CRP-dependent transcriptional activation of ompT in Vibrio cholerae (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In pathogenic Vibrio cholerae, the transmembrane DNA-binding protein ToxR co-ordinates the expression of over 20 genes, including those encoding important virulence factors such as cholera toxin and the toxin-co-regulated pilus. The outer membrane protein OmpT is the only member of the ToxR regulon known to be repressed by ToxR. In this study, we examined the environmental conditions that regulate OmpT expression and demonstrated that ompT transcription is upregulated 14-fold when the bacteria enter late log phase from early log phase. Deletion of the crp gene completely abolishes OmpT expression. Comparison of ompT transcription levels in the isogenic crp−, toxR− and crp−toxR− mutants revealed that (i) in the absence of ToxR, constitutive high-level ompT transcription is dependent on cAMP receptor protein (CRP); (ii) ToxR not only interferes with CRP-dependent ompT activation, but also abolishes the CRP-independent, basal level ompT transcription; thus, the mechanism by which ToxR represses ompT transcription involves both antiactivation and direct repression; (iii) both CRP and ToxR are required for the regulation of OmpT expression by growth phase. To provide further insights into the molecular mecha-nism of CRP-dependent activation of ompT transcription, we demonstrated that CRP-dependent activation requires a CRP binding site centred at −310 of the ompT promoter, without which the interaction of CRP with other CRP binding site(s) more proximal to the promoter results in repression. Mutations in two regions on CRP (AR1 and AR2) that directly contact RNA polymerase (RNAP) abolish activation, suggesting direct interaction of CRP with RNAP from −310 of the ompT promoter via DNA looping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02845.x
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