title: Aggregative adherence fimbria II, a second fimbrial antigen mediating aggregative adherence in enteroaggregative Escherichia coli.
abstract: Enteroaggregative Escherichia coli (EAEC) has been implicated as an agent of pediatric diarrhea in the developing world. We have shown previously that EAEC adheres to HEp-2 cells by virtue of a plasmid-encoded fimbrial adhesin designated aggregative adherence fimbria I (AAF/I), the genes for which have been cloned and sequenced. However, not all EAEC strains express AAF/I. Using TnphoA mutagenesis, we have characterized a novel fimbria (designated AAF/II) which mediates HEp-2 adherence of the human-pathogenic strain 042. AAF/II is 5 nm in diameter and does not bind AAF/I antiserum, as determined by immunogold transmission electron microscopy. TnphoA identified a gene (designated aafA) which bears significant homology to aggA, the fimbrial subunit of AAF/I (25% identity and 47% similarity at the amino acid level). When hyperexpressed and purified by polyhistidine tagging, the AafA protein assembled into 5-nm-diameter filaments which bound anti-AAF/II antiserum. The cloned aafA gene complemented a mutation in the aggA gene to confer fimbrial expression from the AAF/I gene cluster, manifesting phenotypes characteristic of AAF/II but not AAF/I. The aafA mutant did not adhere to human intestinal tissue in culture, suggesting a role for AAF/II in intestinal colonization. By using DNA probes for AAF/I and AAF/II derived from fimbrial biosynthesis genes, we show that AAF/I and AAF/II are each found in only a minority of EAEC strains, suggesting that still more EAEC adhesins exist. Our data suggest that AAF adhesins represent a new family of fimbrial adhesins which mediate aggregative adherence in EAEC.
authors.affiliation: Center for Vaccine Development, Department of Pediatrics, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Czeczulin
authors.forename: S
authors.initials: S
authors.lastname: Balepur
authors.forename: S
authors.initials: S
authors.lastname: Hicks
authors.forename: A
authors.initials: A
authors.lastname: Phillips
authors.forename: R
authors.initials: R
authors.lastname: Hall
authors.forename: M H
authors.initials: MH
authors.lastname: Kothary
authors.forename: F
authors.initials: F
authors.lastname: Navarro-Garcia
authors.forename: J P
authors.initials: JP
authors.lastname: Nataro
mesh_terms: D018830:Adhesins, Escherichia coli / Q000235:genetics*; D000595:Amino Acid Sequence; D001422:Bacterial Adhesion / Q000235:genetics*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003106:Colon / Q000382:microbiology / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000648:ultrastructure; D010861:Fimbriae, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D006386:Hemagglutination Tests; D006801:Humans; D007413:Intestinal Mucosa / Q000382:microbiology* / Q000648:ultrastructure; D007583:Jejunum / Q000382:microbiology / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: C108511:AafA protein, E coli; D018830:Adhesins, Escherichia coli