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:<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>
Project description:References:
1. Xiaomei Zhu, Lan Yin, Leroy Hood, David Galas and Ping Ao, Efficiency, Robustness and Stochasticity of Gene Regulatory networks in Systems biology: Lambda switch as a working example, 2006.
2. Adam Arkin, John Ross and Harley H. McAdams, Stochastic kinetic analysis of developmental pathway bifurcation in phage lambda-infected Escherichia coli cells, 1998, Genetics, 149: 1633-1648.
3. GenBank sequence: NC_001416 is the whole genome sequence of phage lambda.
Project description:Bacteriophage lambda is one of the most extensively studied organisms, and has been a primary model for understanding basic modes of genetic regulation. Here we examine the progress of lambda gene expression during phage development by ribosome profiling, and thereby provide a very high resolution view of lambda gene expression. The known genes are expressed in a predictable fashion, authenticating the analysis. But many previously unappreciated potential open reading frames become apparent in the expression analysis, revealing an unexpected complexity in the pattern of lambda gene function.
Project description:Gardner2000 - genetic toggle switch in E.coli
The behaviour of the genetic toggle switch and the conditions for bistability has been studies using a synthetic, bistable gene circuit.
This model is described in the article:
Construction of a genetic toggle switch in Escherichia coli.
Gardner TS, Cantor CR, Collins JJ
Nature. 2000 Jan 20;403(6767):339-42.
Abstract:
It has been proposed' that gene-regulatory circuits with virtually any desired property can be constructed from networks of simple regulatory elements. These properties, which include multistability and oscillations, have been found in specialized gene circuits such as the bacteriophage lambda switch and the Cyanobacteria circadian oscillator. However, these behaviours have not been demonstrated in networks of non-specialized regulatory components. Here we present the construction of a genetic toggle switch-a synthetic, bistable gene-regulatory network-in Escherichia coli and provide a simple theory that predicts the conditions necessary for bistability. The toggle is constructed from any two repressible promoters arranged in a mutually inhibitory network. It is flipped between stable states using transient chemical or thermal induction and exhibits a nearly ideal switching threshold. As a practical device, the toggle switch forms a synthetic, addressable cellular memory unit and has implications for biotechnology, biocomputing and gene therapy.
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2024-09-02 | BIOMD0000000507 | BioModels
Project description:Complete Genome Assembly and Annotation of Escherichia coli Bacteriophage 55 (RGB-004)
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