title: The flagellar sigma factor FliA regulates adhesion and invasion of Crohn disease-associated Escherichia coli via a cyclic dimeric GMP-dependent pathway.
abstract: The invasion of intestinal epithelial cells by the Crohn disease-associated adherent-invasive Escherichia coli (AIEC) strain LF82 depends on surface appendages, such as type 1 pili and flagella. The absence of flagella in the AIEC strain LF82 results in a concomitant loss of type 1 pili. Here, we show that flagellar regulators, transcriptional activator FlhD(2)C(2), and sigma factor FliA are involved in the coordination of flagellar and type 1 pili synthesis. In the deletion mutants lacking these regulators, type 1 pili synthesis, adhesion, and invasion were severely decreased. FliA expressed alone in trans was sufficient to restore these defects in both the LF82-DeltaflhD and LF82-DeltafliA mutants. We related the loss of type 1 pili to the decreased expression of the FliA-dependent yhjH gene in the LF82-DeltafliA mutant. YhjH is an EAL domain phosphodiesterase involved in degradation of the bacterial second messenger cyclic dimeric GMP (c-di-GMP). Increased expression of either yhjH or an alternative c-di-GMP phosphodiesterase, yahA, partially restored type 1 pili synthesis, adhesion, and invasion in the LF82-DeltafliA mutant. Deletion of the GGDEF domain diguanylate cyclase gene, yaiC, involved in c-di-GMP synthesis in the LF82-DeltafliA mutant also partially restored these defects, whereas overexpression of the c-di-GMP receptor YcgR had the opposite effect. These findings show that in the AIEC strain LF82, FliA is a key regulatory component linking flagellar and type 1 pili synthesis and that its effect on type 1 pili is mediated, at least in part, via a c-di-GMP-dependent pathway.
authors.affiliation: Université Clermont 1, Pathogénie Bactérienne Intestinale, Institut National de la Recherche Agronomique, Unité Sous Contrat 2018 (USC INRA 2018), Clermont-Ferrand F-63001, France; Institut Universitaire de Technologie en Génie Biologique, Aubière F-63172, France. Electronic address: laurent.claret@u-clermont1.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Claret
authors.affiliation: Université Clermont 1, Pathogénie Bactérienne Intestinale, Institut National de la Recherche Agronomique, Unité Sous Contrat 2018 (USC INRA 2018), Clermont-Ferrand F-63001, France; Institut Universitaire de Technologie en Génie Biologique, Aubière F-63172, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Miquel
authors.affiliation: Université Clermont 1, Pathogénie Bactérienne Intestinale, Institut National de la Recherche Agronomique, Unité Sous Contrat 2018 (USC INRA 2018), Clermont-Ferrand F-63001, France.
authors.forename: Natacha
authors.initials: N
authors.lastname: Vieille
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, 82071.
authors.forename: Dmitri A
authors.initials: DA
authors.lastname: Ryjenkov
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, 82071.
authors.forename: Mark
authors.initials: M
authors.lastname: Gomelsky
authors.affiliation: Université Clermont 1, Pathogénie Bactérienne Intestinale, Institut National de la Recherche Agronomique, Unité Sous Contrat 2018 (USC INRA 2018), Clermont-Ferrand F-63001, France; Institut Universitaire de Technologie en Génie Biologique, Aubière F-63172, France.
authors.forename: Arlette
authors.initials: A
authors.lastname: Darfeuille-Michaud
mesh_terms: D003424:Crohn Disease / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D007413:Intestinal Mucosa / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D009154:Mutation; D017434:Protein Structure, Tertiary; D012808:Sigma Factor / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation