title: Identification and mechanism of evolution of new alleles coding for the AIDA-I autotransporter of porcine pathogenic Escherichia coli.
abstract: Autotransporters are a large family of virulence factors of Gram-negative bacterial pathogens. The autotransporter adhesin involved in diffuse adherence (AIDA-I) is an outer membrane protein of Escherichia coli, which allows binding to epithelial cells as well as the autoaggregation of bacteria. AIDA-I is glycosylated by a specific heptosyltransferase encoded by the aah gene that forms an operon with the aidA gene. aidA is highly prevalent in strains that cause disease in pigs. Nevertheless, there are only two published whole-length sequences for this gene. In this study, we sequenced the aah and aidA genes of 24 aidA-positive porcine strains harboring distinct virulence factor profiles. We compared the obtained sequences and performed phylogenetic and pulsed-field electrophoresis analyses. Our results suggest that there are at least 3 different alleles for aidA, which are associated with distinct virulence factor profiles. The genes are found on high-molecular-weight plasmids and seem to evolve via shuffling mechanisms, with one of the sequences showing evidence of genetic recombination. Our work suggests that genetic plasticity allows the evolution of aah-aidA alleles that are selected during pathogenesis.
authors.affiliation: Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Côté
authors.forename: Frédéric
authors.initials: F
authors.lastname: Berthiaume
authors.forename: Sébastien
authors.initials: S
authors.lastname: Houle
authors.forename: John M
authors.initials: JM
authors.lastname: Fairbrother
authors.forename: Charles M
authors.initials: CM
authors.lastname: Dozois
authors.forename: Michael
authors.initials: M
authors.lastname: Mourez
mesh_terms: D018830:Adhesins, Escherichia coli / Q000235:genetics*; D000483:Alleles; D000818:Animals; D016000:Cluster Analysis; D032621:DNA Shuffling; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics; D019143:Evolution, Molecular; D016695:Glycosyltransferases / Q000235:genetics; D008969:Molecular Sequence Data; D058889:Molecular Typing; D010802:Phylogeny; D010957:Plasmids; D017422:Sequence Analysis, DNA; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics*
chemical_list: C075559:AIDA-I protein, E coli; D018830:Adhesins, Escherichia coli; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D037521:Virulence Factors; D016695:Glycosyltransferases; C433803:autotransporter-adhesin-heptosyltransferase, E coli