title: Systematic identification and sequence analysis of the genomic islands of the enteropathogenic Escherichia coli strain B171-8 by the combined use of whole-genome PCR scanning and fosmid mapping.
abstract: Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are diarrheagenic pathogens that colonize the intestinal tract through the formation of attaching and effacing lesions, induced by effectors translocated via a type III secretion system (T3SS) encoded on the locus of enterocyte effacement (LEE). In EHEC O157, numerous virulence factors, including around 40 T3SS effectors, have been identified. Most of them are encoded on genomic islands (GEIs) such as prophages and integrative elements. For EPEC, however, no systematic search of GEIs and virulence-related genes carried therein has been done, and only a limited number of virulence factors have been identified so far. In this study, we performed a systemic and genome-wide survey of the GEIs in strain B171-8, one of the prototype strains of EPEC, by the combined use of whole-genome PCR scanning and fosmid mapping and identified 22 large GEIs, including nine lambda-like prophages, three P2-like prophages, the LEE, and three additional integrative elements. On these prophages and integrative elements, we found genes for a set of T3SS proteins, a total of 33 T3SS effectors or effector homologues, and 12 other virulence factors which include five nonfimbrial adhesins. Most of the T3SS effector families identified are also present in EHEC O157, but B171-8 possesses a significantly smaller number of effectors. Not only the presence or absence of Shiga toxin genes but also the difference in the T3SS effector repertoire should be considered in analyzing the pathogenicity of EPEC and EHEC strains.
authors.affiliation: Division of Bioenvironmental Science, Frontier Science Research Center, Department of Infectious Diseases, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 899-1692, Japan.
authors.forename: Yoshitoshi
authors.initials: Y
authors.lastname: Ogura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Abe
authors.forename: Keisuke
authors.initials: K
authors.lastname: Katsura
authors.forename: Ken
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Md
authors.initials: M
authors.lastname: Asadulghani
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iguchi
authors.forename: Tadasuke
authors.initials: T
authors.lastname: Ooka
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakayama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yamashita
authors.forename: Masahira
authors.initials: M
authors.lastname: Hattori
authors.forename: Toru
authors.initials: T
authors.lastname: Tobe
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hayashi