Project description:In 2011, in Germany, Escherichia coli O104:H4 caused the enterohemorrhagic E. coli (EHEC) outbreak with the highest incidence rate of hemolytic uremic syndrome. This pathogen carries an exceptionally potent combination of EHEC- and enteroaggregative E. coli (EAEC)-specific virulence factors. Here, we identified an E. coli O104:H4 isolate that carried a single nucleotide polymorphism (SNP) in the start codon (ATG>ATA) of rpoS, encoding the alternative sigma factor S. The rpoS ATG>ATA SNP was associated with enhanced EAEC-specific virulence gene expression. Deletion of rpoS in E. coli O104:H4 Dstx2 and typical EAEC resulted in a similar effect. Both rpoS ATG>ATA and DrpoS strains exhibited stronger virulence-related phenotypes in comparison to wild type. Using promoter-reporter gene fusions, we demonstrated that wild-type RpoS repressed aggR, encoding the main regulator of EAEC virulence. In summary, our work demonstrates that RpoS acts as a global repressor of E. coli O104:H4 virulence, primarily through an AggR-dependent mechanism.
Project description:Secreted proteins constitute a major part of virulence factors that are responsible for pathogenesis caused by gram negative bacteria. Enterohemorrhagic Escherichia coli (E. coli), EHEC O157:H7 is the major pathogen often causing outbreaks. There is growing evidence that non-O157:H7 E. coli strains may also be involved in the recent outbreaks. However, there is no systematic study describing differential secreted proteins from non-O157:H7 E. coli strains. Here, we have applied isobaric tag-based TMT labeling combined with high-resolution Fourier transform mass spectrometry to study the differential secretome analysis of major non-O157:H7 E. coli strains, O103, O111, O121, O145, O26 and O45, which is known as diarrhea inducing non-O175:H7 ATCC “big six” serogroup E. coli strains. We identified 1,240 proteins quantitatively identified, 565 proteins were found to be secreted as predicted by PSORTb and SecretomeP. We identified 310 proteins containing signal peptide and 255 proteins as secreted. We identified 20 strain specific proteins with in big-six group and was confirmed by proteogenomics approach. Further we enriched and have shown relative expression of type III secretion system. To our knowledge, this study is the first comparative proteomic study on secretome of E. coli big six serogroup and the several of these strain specific secreted proteins can be further studied to develop potential markers for identification and strain level differentiation. Moreover, the results of this study can be utilized in several applications, including food safety, diagnostics of E. coli outbreaks, and biodefense.
Project description:An experiment to identify the downstream targets of PatE, a prophage encoded AraC-like transcriptional regulator, in transcriptional activation of acid-resistance pathways of enterohemorrhagic Escherichia coli strain EDL933 using deletion and complementation strains (Delta3 and Delta3_1, respectively).
Project description:Here, we investigated the impact of Stx2 phage carriage on Escherichia coli (E. coli) K-12 MG1655 host gene expression. Using quantitative RNA-seq analysis, we compared the transcriptome of naïve MG1655 and the lysogens carrying the Stx2 phage of the 2011 E. coli O104:H4 outbreak strain or of the E. coli O157:H7 strain PA8, which share high degree of sequence similarity.
Project description:Diffuse outbreak investigation and development of rapid screening method by using whole genome sequences of enterohemorrhagic Escherichia coli O121
Project description:Transcription profiles in BL21, BL21/pOri1 and BL21/pOri2 were analysed using DNA microarray technology. BL21, BL21/pOri1 or BL21/pOri2 strains were cultured at chemostat status and harvested after the cultivation arrived steady status. Keywords: Effects of plasmid DNA on Escherichia coli metabolism
Project description:The Escherichia coli strain Nissle 1917 (EcN) is used as a probiotic for the treatment of certain gastrointestinal diseases in several European and non-European countries. In vitro studies showed EcN to efficiently inhibit the production of Shiga toxin (Stx) by Stx producing E. coli (STEC) such as Enterohemorrhagic E. coli (EHEC). The occurrence of the latest EHEC serotype (O104:H4) responsible for the great outbreak in 2011 in Germany was due to the infection of an enteroaggregative E. coli by a Stx 2-encoding lambdoid phage turning this E. coli into a lysogenic and subsequently into a Stx producing strain. Since EHEC infected persons are not recommended to be treated with antibiotics, EcN might be an alternative medication. However, because a harmless E. coli strain might be converted into a Stx-producer after becoming host to a stx encoding prophage, we tested EcN for stx-phage genome integration. Our experiments revealed the resistance of EcN towards not only stx-phages but also against the lambda phage. This resistance was not based on the lack of or by mutated phage receptors. Rather the expression of certain genes (superinfection exclusion B (sieB) and a phage repressor (pr) gene) of a defective prophage of EcN was involved in the complete resistance of EcN to infection by the stx- and lambda phage. Obviously, EcN cannot be turned into a Stx producer. Furthermore, we observed EcN to inactivate phages and thereby to protect E. coli K-12 strains against infection by stx- as well as lambda-phages. Inactivation of lambda-phages was due to binding of lambda-phages to LamB of EcN whereas inactivation of stx-phages was caused by a thermostable protein of EcN. These properties together with its ability to inhibit Stx production make EcN a good candidate for the prevention of illness caused by EHEC and probably for the treatment of already infected people.
Project description:Pathogenic biofilms have been associated with persistent infections due to their high resistance to antimicrobial agents. To identify non-toxic biofilm inhibitors for enterohemorrhagic Escherichia coli O157:H7, indole-3-acetaldehyde was used and reduced E. coli O157:H7 biofilm formation. Global transcriptome analyses revealed that indole-3-acetaldehyde most repressed two curli operons, csgBAC and csgDEFG, and induced tryptophanase (tnaAB) in E. coli O157:H7 biofilm cells. Electron microscopy showed that indole-3-acetaldehyde reduced curli production in E. coli O157:H7. Together, this study shows that Actinomycetales are an important resource of biofilm inhibitors as well as antibiotics.