Project description:Analysis of gene expression of mid log phase cultures of Escherichia coli Ancestor strain, and high temperature evolved lines 42-1, 42-2 and 42-3. Keywords: other
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:A whole genome screen was used to assay every gene of Escherichia coli strain BW25113 to identify genes involved in susceptibility to the monobactam (beta-lactam) antibiotic aztreonam. The methodology has been called TraDIS-Xpress, and is a version of TraDIS or Tn-seq. A transposon mutant library consisting of several hundred thousand mutants was constructed using a Tn5-derived transposon incorporating an inducible outward transcribing promoter. All the mutants were grown in LB broth cultures supplemented with aztreonam at 2 x, 1 x, 0.5 x and 0.25 x MIC with induction of the transposon promoter using 0.2 mM IPTG or 1 mM IPTG or without induction. Following growth, mutants with increased susceptibility show reduced numbers and those with reduced susceptibility show increased numbers. Each condition was performed in duplicate. The methodology enable genes to be assayed by insertional inactivation or by changes in expression. Expression changes result from altered transcription from upstream transposon insertions transcribing into the gene, or downstream insertions transcribing into the gene in the reverse direction leading to RNA interference through the generation of reverse and complementary RNA. Thus, essential genes into which transposon insertions are not tolerated may be assayed also by changes in numbers of upstream or downstream insertion mutants. Changes to high throughput sequencing protocols permit the generation of nucleotide sequence reads from the known transposon sequences into the surrounding insertion site for all the mutants in the mixture simultaneously. Matching the sequence of the reads to the genome nucleotide sequence of E. coli BW25113 then allows the precise locations of all the transposon insertion sites of all the mutants to be mapped simultaneously. The relative changes in mutants between control (without) and selective condition (with aztreonam) then indicates which genes are involved in susceptibility. The numbers of sequence reads that match is reflected by the number of mutants, and so the degree of susceptibility can also be estimated.
Project description:Responses of Escherichia coli W3110gyrb234 as they are upshifted to 42C Escherichia coli W3110gyrb234 cells sampled at several time points (2,5, 10, 40 min) as they are shifted to 42 C in LB, vs 0 min before upshift in LB
Project description:While ESBL and AmpC beta-lactamases barely degrade carbapenems, they are able to bind them and prevent them from interacting with penicillin binding proteins thereby preventing their effect. When these beta-lactamases are expressed at a high level and combined with a decreased influx of carbapenems due to a decrease in membrane permeability, Enterobacterales can become resistant to carbapenems. In this study we developed a LC-MS/MS assay for the detection of the E. coli porins OmpC and OmpF, it’s chromosomal AmpC beta-lactamase and the plasmid-mediated CMY-2 beta-lactamase. Subsequently, we cultured CMY-2 positive E. coli isolates in the presence of meropenem and analyzed mutants that showed increased resistance to meropenem using our developed assay and western blot. In all five selected strains, a decrease in OmpC and/or OmpF was the first event towards an increase in meropenem minimum inhibitory concentrations (MICs). Subsequently, in four of the five isolate series, MICs increased further after an increase in CMY-2-like production.
Project description:NsrR is a nitric oxide sensitive regulator of transcription. In Escherichia coli, NsrR is a repressor of the hmp gene encoding the flavohemoglobin that detoxifies nitric oxide. Several other transcription units (including ytfE, ygbA and hcp-hcr) are known to be subject to regulation by NsrR. In this study, chromatin immunoprecipitation and microarray analysis was used to identify NsrR binding sites in the chromosome of Escherichia coli strain MG1655. Keywords: ChIP-chip
Project description:Primary objectives: The study investigates whether a Escherichia coli Nissle-suspenison has a (preventive) antidiarrheal effect in patients with tumors who are treated with chemotherapeutic schemes which are associated with increased occurances of diarrhea. Diarrhea caused by treatment are thought to be reduced in intensity and/or frequency by the treatment with Escherichia coli Nissle-Suspension.
Primary endpoints: Common toxicity criteria (CTC) for diarrhea
Project description:<p>Traveler's diarrhea (TD) is caused by enterotoxigenic Escherichia coli (ETEC), other pathogenic gram-negative pathogens, norovirus and some parasites. Nevertheless, standard diagnostic methods fail to identify pathogens in more than 30% of TD patients, so it is predicted that new pathogens or groups of pathogens may be causative agents of disease. A comprehensive metagenomic study of the fecal microbiomes from 23 TD patients and seven healthy travelers was performed, all of which tested negative for the known etiologic agents of TD in standard tests. Metagenomic reads were assembled and the resulting contigs were subjected to semi-manual binning to assemble independent genomes from metagenomic pools. Taxonomic and functional annotations were conducted to assist identification of putative pathogens. We extracted 560 draft genomes, 320 of which were complete enough to be enough characterized as cellular genomes and 160 of which were bacteriophage genomes. We made predictions of the etiology of disease in individual subjects based on the properties and features of the recovered cellular genomes. Three subtypes of samples were observed. First were four patients with low diversity metagenomes that were predominated by one or more pathogenic E. coli strains. Annotation allowed prediction of pathogenic type in most cases. Second, five patients were co-infected with E. coli and other members of the Enterobacteriaceae, including antibiotic resistant Enterobacter, Klebsiella, and Citrobacter. Finally, several samples contained genomes that represented dark matter. In one of these samples we identified a TM7 genome that phylogenetically clustered with a strain isolated from wastewater and carries genes encoding potential virulence factors. We also observed a very high proportion of bacteriophage reads in some samples. The relative abundance of phage was significantly higher in healthy travelers when compared to TD patients. Our results highlight that assembly-based analysis revealed that diarrhea is often polymicrobial and includes members of the Enterobacteriaceae not normally associated with TD and have implicated a new member of the TM7 phylum as a potential player in diarrheal disease. </p>