title: Role of the Helicobacter hepaticus flagellar sigma factor FliA in gene regulation and murine colonization.
abstract: The enterohepatic Helicobacter species Helicobacter hepaticus colonizes the murine intestinal and hepatobiliary tract and is associated with chronic intestinal inflammation, gall stone formation, hepatitis, and hepatocellular carcinoma. Thus far, the role of H. hepaticus motility and flagella in intestinal colonization is unknown. In other, closely related bacteria, late flagellar genes are mainly regulated by the sigma factor FliA (sigma(28)). We investigated the function of the H. hepaticus FliA in gene regulation, flagellar biosynthesis, motility, and murine colonization. Competitive microarray analysis of the wild type versus an isogenic fliA mutant revealed that 11 genes were significantly more highly expressed in wild-type bacteria and 2 genes were significantly more highly expressed in the fliA mutant. Most of these were flagellar genes, but four novel FliA-regulated genes of unknown function were identified. H. hepaticus possesses two identical copies of the gene encoding the FliA-dependent major flagellin subunit FlaA (open reading frames HH1364 and HH1653). We characterized the phenotypes of mutants in which fliA or one or both copies of the flaA gene were knocked out. flaA_1 flaA_2 double mutants and fliA mutants did not synthesize detectable amounts of FlaA and possessed severely truncated flagella. Also, both mutants were nonmotile and unable to colonize mice. Mutants with either flaA gene knocked out produced flagella morphologically similar to those of wild-type bacteria and expressed FlaA and FlaB. flaA_1 mutants which had flagella but displayed reduced motility did not colonize mice, indicating that motility is required for intestinal colonization by H. hepaticus and that the presence of flagella alone is not sufficient.
authors.affiliation: Hannover Medical School, Institute for Medical Microbiology and Hospital Epidemiology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Sterzenbach
authors.forename: Lucie
authors.initials: L
authors.lastname: Bartonickova
authors.forename: Wiebke
authors.initials: W
authors.lastname: Behrens
authors.forename: Birgit
authors.initials: B
authors.lastname: Brenneke
authors.forename: Jessika
authors.initials: J
authors.lastname: Schulze
authors.forename: Friederike
authors.initials: F
authors.lastname: Kops
authors.forename: Elaine Y
authors.initials: EY
authors.lastname: Chin
authors.forename: Elena
authors.initials: E
authors.lastname: Katzowitsch
authors.forename: David B
authors.initials: DB
authors.lastname: Schauer
authors.forename: James G
authors.initials: JG
authors.lastname: Fox
authors.forename: Sebastian
authors.initials: S
authors.lastname: Suerbaum
authors.forename: Christine
authors.initials: C
authors.lastname: Josenhans
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D005408:Flagellin / Q000235:genetics; D016481:Helicobacter Infections / Q000382:microbiology*; D044923:Helicobacter hepaticus / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D054884:Host-Pathogen Interactions; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C064971:FliA protein, Bacteria; D012808:Sigma Factor; D005408:Flagellin