Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. col 0157:H7 are intestinal pathogens that profoundly damage the microvilli and subapical cytoskeleton of epithelial cells. Here we report finding in EPEC a 35-kbp locus containing several regions implicated in formation of these lesions. DNA probes throughout this locus hybridize to E. coli 0157:H7 and other pathogens of three genera that cause similar lesions but do not hybridize to avirulent members of the same species. The EPEC locus and a different virulence locus of uropathogenic E. coli insert into the E. coli chromosome at the identical site and share highly similar sequences near the point of insertion.
Enteropathogenic Escherichia coli (EPEC) causes a characteristic histopathology in intestinal epithelial cells called the attaching and effacing lesion. Although the histopathological lesion is well described the bacterial factors responsible for it are poorly characterized. We have identified four EPEC chromosomal genes whose predicted protein sequences are similar to components of a recently described secretory pathway (type III) responsible for exporting proteins lacking a typical signal sequence. We have designated the genes sepA, sepB, sepC, and sepD (sep, for secretion of E. coli proteins). The predicted Sep polypeptides are similar to the Lcr (low calcium response) and Ysc (yersinia secretion) proteins of Yersinia species and the Mxi (membrane expression of invasion plasmid antigens) and Spa (surface presentation of antigens) regions of Shigella flexneri. Culture supernatants of EPEC strain E2348/69 contain several polypeptides ranging in size from 110 kDa to 19 kDa. Proteins of comparable size were recognized by human convalescent serum from a volunteer experimentally infected with strain E2348/69. A sepB mutant of EPEC secreted only the 110-kDa polypeptide and was defective in the formation of attaching and effacing lesions and protein-tyrosine phosphorylation in tissue culture cells. These phenotypes were restored upon complementation with a plasmid carrying an intact sepB gene. These data suggest that the EPEC Sep proteins are components of a type III secretory apparatus necessary for the export of virulence determinants.Enteropathogenic Escherichia coli (EPEC) causes infantile diarrhea throughout the world. EPEC infections result in the formation of attaching and effacing (AE) lesions which are characterized by effacement of intestinal microvilli, intimate adherence of bacteria to enterocytes, and accumulation of polymerized actin and other cytoskeletal components in the eukaryotic cell. Filamentous actin accumulates below the bacteria, resulting in the formation of cup-like pedestals (1, 2). Several signal transduction mechanisms have been associated with AE lesion formation, including tyrosine phosphorylation of a 90-kDa host cell protein (Hp9O) (3), fluxes in inositol phosphate levels (4), increased intracellular Ca2+ levels (5), and phosphorylation of myosin light chain (6). We recently described a large (35-kb) region in the EPEC chromosome, termed LEE (locus of enterocyte effacement), that encodes all of the virulence determinants for AE lesion formation so far identified (7). Two chromosomal loci within the LEE, eaeA and eaeB (eae, for E. coli attaching and effacing
Helicobacter pylori colonizes the stomach of half of the world's population, causing a wide spectrum of disease ranging from asymptomatic gastritis to ulcers to gastric cancer. Although the basis for these diverse clinical outcomes is not understood, more severe disease is associated with strains harboring a pathogenicity island. To characterize the genetic diversity of more and less virulent strains, we examined the genomic content of 15 H. pylori clinical isolates by using a whole genome H. pylori DNA microarray. We found that a full 22% of H. pylori genes are dispensable in one or more strains, thus defining a minimal functional core of 1281 H. pylori genes. While the core genes encode most metabolic and cellular processes, the strain-specific genes include genes unique to H. pylori, restriction modification genes, transposases, and genes encoding cell surface proteins, which may aid the bacteria under specific circumstances during their long-term infection of genetically diverse hosts. We observed distinct patterns of the strainspecific gene distribution along the chromosome, which may result from different mechanisms of gene acquisition and loss. Among the strain-specific genes, we have found a class of candidate virulence genes identified by their coinheritance with the pathogenicity island. Helicobacter pylori is a highly host-adapted bacterial pathogen that establishes a chronic infection in the human stomach and has no known animal or environmental reservoirs (1). Epidemiological and serological studies have revealed that H. pylori strains containing the CagA protein are associated with more severe disease (2) and harbor a 40-kb pathogenicity island (PAI) (3, 4). The PAI encodes a bacterial type IV secretory system that secretes and translocates the CagA protein into host cells (5-8), where it is phosphorylated by a host-cell kinase and causes morphological changes (7). The PAI also induces IL-8 production by host cells independent of the CagA protein (9 -11). Efforts to classify H. pylori strains further by DNA fingerprinting uncovered extensive diversity (12, 13). The sequencing of two H. pylori genomes from independent strains, both containing the PAI, revealed that much of this diversity is silent at the amino acid level and thus at the functional gene level (14, 15). Here we used a H. pylori DNA microarray to examine the genomic composition of H. pylori clinical isolates containing and lacking the PAI at the level of individual genes to characterize the extent of genetic diversity between strains and to search for new candidate virulence determinants. Materials and MethodsPCR Primer Design. The elements of our microarray consisted of large (mean size, 817 base pairs; 10th percentile, 130 base pairs; 90th percentile, 1,967 base pairs) DNA fragments corresponding to unique segments of individual open reading frames (ORFs). These fragments were generated by PCRs using gene-specific primers. We aimed to include in our array the superset of ORFs from both published genomes. When an ORF was present in bo...
SummaryAttaching 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 signaltransduction 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.