title: Genetic structure and distribution of the colibactin genomic island among members of the family Enterobacteriaceae.
abstract: A genomic island encoding the biosynthesis and secretion pathway of putative hybrid nonribosomal peptide-polyketide colibactin has been recently described in Escherichia coli. Colibactin acts as a cyclomodulin and blocks the eukaryotic cell cycle. The origin and prevalence of the colibactin island among enterobacteria are unknown. We therefore screened 1,565 isolates of different genera and species related to the Enterobacteriaceae by PCR for the presence of this DNA element. The island was detected not only in E. coli but also in Klebsiella pneumoniae, Enterobacter aerogenes, and Citrobacter koseri isolates. It was highly conserved among these species and was always associated with the yersiniabactin determinant. Structural variations between individual strains were only observed in an intergenic region containing variable numbers of tandem repeats. In E. coli, the colibactin island was usually restricted to isolates of phylogenetic group B2 and inserted at the asnW tRNA locus. Interestingly, in K. pneumoniae, E. aerogenes, C. koseri, and three E. coli strains of phylogenetic group B1, the functional colibactin determinant was associated with a genetic element similar to the integrative and conjugative elements ICEEc1 and ICEKp1 and to several enterobacterial plasmids. Different asn tRNA genes served as chromosomal insertion sites of the ICE-associated colibactin determinant: asnU in the three E. coli strains of ECOR group B1, and different asn tRNA loci in K. pneumoniae. The detection of the colibactin genes associated with an ICE-like element in several enterobacteria provides new insights into the spread of this gene cluster and its putative mode of transfer. Our results shed light on the mechanisms of genetic exchange between members of the family Enterobacteriaceae.
authors.affiliation: Julius-Maximilians-Universität Würzburg, Institut für Molekulare Infektionsbiologie, Röntgenring 11, D-97070 Würzburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Putze
authors.forename: Claire
authors.initials: C
authors.lastname: Hennequin
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Nougayrède
authors.forename: Wenlan
authors.initials: W
authors.lastname: Zhang
authors.forename: Stefan
authors.initials: S
authors.lastname: Homburg
authors.forename: Helge
authors.initials: H
authors.lastname: Karch
authors.forename: Marie-Agnés
authors.initials: MA
authors.lastname: Bringer
authors.forename: Corinne
authors.initials: C
authors.lastname: Fayolle
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Carniel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Rabsch
authors.forename: Tobias A
authors.initials: TA
authors.lastname: Oelschlaeger
authors.forename: Eric
authors.initials: E
authors.lastname: Oswald
authors.forename: Christiane
authors.initials: C
authors.lastname: Forestier
authors.forename: Jörg
authors.initials: J
authors.lastname: Hacker
authors.forename: Ulrich
authors.initials: U
authors.lastname: Dobrindt
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial / Q000235:genetics*; D044404:Genomic Islands / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010641:Phenotype; D016133:Polymerase Chain Reaction
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins