title: Regulatory and functional co-operation of flagella and type 1 pili in adhesive and invasive abilities of AIEC strain LF82 isolated from a patient with Crohn's disease.
abstract: Genetic determinants that co-operate with type 1 pili to mediate invasion were sought for in adherent-invasive Escherichia coli strain LF82 isolated from a patient with Crohn's disease. Two mutants selected for their impaired ability to invade epithelial cells carried insertions of a TnphoA transposon within genes of the flagellar regulon. An isogenic mutant LF82-DeltafliC deleted for the flagellin-encoding gene did not adhere, did not invade and, surprisingly, expressed only a few type 1 pili. Type 1 pili downregulation resulted from a preferential switch towards the off-position of the invertible DNA element located upstream of the fim operon. This was also correlated with a decrease in the flagellar regulator flhDC mRNA levels, suggesting that the transcriptional regulator FlhD2C2 could control type 1 pili expression directly or indirectly. Transformation with a cloned fim operon allowed bypass of the type 1 pili downexpression in the LF82-DeltafliC mutant. Thus, we showed that flagella play a direct role in the adhesion process via active motility. In addition to downregulating type 1 pili expression, flagella also play an undefined role in strain LF82 invasion, which is not restricted to motility or flagellar structure, but could be related to co-ordinate expression of invasive determinants.
authors.affiliation: Pathogénie Bactérienne Intestinale, Laboratoire de Bactériologie, Université d'Auvergne, 28 place Henri Dunant, 63001 Clermont-Ferrand, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Barnich
authors.forename: Jérôme
authors.initials: J
authors.lastname: Boudeau
authors.forename: Laurent
authors.initials: L
authors.lastname: Claret
authors.forename: Arlette
authors.initials: A
authors.lastname: Darfeuille-Michaud
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D002478:Cells, Cultured; D003424:Crohn Disease / Q000382:microbiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology / Q000648:ultrastructure; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D005407:Flagella / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D009876:Operon; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D015534:Trans-Activators; C090553:flhD protein, E coli