Project description:DNA microarray analyses was carried out to identify genes which are differentially expressed in E. coli when mutant variants of pdxJ are expressed that rescue growth of auxotrophic E. coli delta serB and delta serC mutants.
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:We compared several E. coli AlkB variants for their applications in facilitating sequencing of tRNA species in total RNA. These proteins are wild type AlkB, mutant D135S and mutant D135T.
Project description:Curli are adhesive fimbriae of Enterobactericaeae and are involved in surface attachment, cell aggregation and biofilm formation. We previously reported that natural curli variants of E. coli O157:H7 (EcO157) displayed distinct acid resistance; however, this difference was not linked to the curli fimbriae per se. Here, we investigated the underlying molecular basis of this phenotypic divergence between the curli variants. Among curli-producing (C+) variants isolated from the 1993 U.S. hamburger-associated outbreaks strains, we identified large deletions in the rcsB gene that encodes the response regulator of RcsCDB two-component signal transduction system of rcsB ,. Further comparison of stress fitness revealed that C+ variants were also significantly more sensitive to heat shock, but remained similar resistance to osmotic stress and oxidative damage as curli-deficient (C-) variants. Transcriptomics analysis uncovered a large number of differentially expressed genes between the curli variants, characterized by the enhanced expression of genes related to biofilm formation, virulence, catabolic activity and nutrients uptake, but marked decrease in transcription of genes related to various stress resistance in C+ variants. Supplying C+ variants with a functional rcsB restored cells resistance to heat shock and acid challenge, but blocked the curli production, confirming that inactivation of RcsB in C+ variants was the basis of fitness segregation within the EcO157population. This study provides an example of how genome instability of EcO157promotes the intra-population diversification, generating sub-populations carrying an array of distinct phenotypes that may confer the pathogen survival advantages in host and nonhost environments.
Project description:To understand the influence of global transcription regulators Fis and CRP on global gene expression in different growth phases of E. coli.
Project description:Comparison of Escherichia coli proteomics of different DNA sequence binding proteins and identification of heterologous expressed protein
Project description:We determined the global gene expression profiles of wildtype, dam, dam mutS, and mutS mutant E. coli strains. Keywords: Basal gene expression comparison
Project description:RpoS is a conserved stress regulator that plays a critical role in survival under stress conditions in Escherichia coli and other γ-proteobacteria. RpoS is also involved in virulence of many pathogens including Salmonella and Vibrio species. Though well characterized in non-pathogenic E. coli K12 strains, the effect of RpoS on transcriptome expression has not been examined in pathogenic isolates. E. coli O157:H7 is a serious human enteropathogen, possessing a genome 20% larger than that of E. coli K12, and many of the additional genes are required for virulence. The genomic difference may result in substantial changes in RpoS-regulated gene expression. To test this, we compared the transcriptional profile of wild type and rpoS mutants of the E. coli O157:H7 EDL933 type strain. The rpoS mutation had a pronounced effect on gene expression in stationary phase, and more than 1,000 genes were differentially expressed (two-fold, p<0.05). By contrast, we found 11 genes expressed differently in exponential phase. Western blot analysis revealed that, as expected, RpoS level was low in exponential phase and substantially increased in stationary phase. The defect in rpoS resulted in impaired expression of genes responsible for stress response (e.g., gadA, katE and osmY), arginine degradation (astCADBE), putrescine degradation (puuABCD), fatty acid oxidation (fadBA and fadE), and virulence (ler, espI and cesF). For EDL933-specific genes on O-islands, we found 50 genes expressed higher in wild type EDL933 and 49 genes expressed higher in the rpoS mutants. The protein levels of Tir and EspA, two LEE-encoded virulence factors, were elevated in the rpoS mutants under LEE induction conditions. Our results show that RpoS has a profound effect on global gene expression in the pathogenic strain O157:H7 EDL933, and the identified RpoS regulon, including many EDL933-specific genes, differs substantially from that of laboratory K12 strains. In this study, we characterized the RpoS regulon of E. coli O157:H7 strain EDL933 using microarray analysis.