title: Chemotactic motility is required for invasion of the host by the fish pathogen Vibrio anguillarum.
abstract: The role of the flagellum and motility in the virulence of the marine fish pathogen Vibrio anguillarum was examined. Non-motile mutants were generated by transposon mutagenesis. Infectivity studies revealed that disruption of the flagellum and subsequent loss of motility correlated with an approximate 500-fold decrease in virulence when fish were inoculated by immersion in bacteria-containing water. However, the flagellar filament and motility were not required for pathogenicity following intraperitoneal injection of fish. The transposon-insertion site for six mutants was determined by cloning and sequencing of the Vibrio DNA flanking the transposon. V. anguillarum genes whose products showed strong homology to proteins with an established role in flagellum biosynthesis were identified. One of the aflagellate mutants had a transposon insertion in the rpoN gene of V. anguillarum. This rpoN mutant failed to grow at low concentrations of available iron and was avirulent by both the immersion and intraperitoneal modes of inoculation. A chemotaxis gene, cheR, was located upstream of one transposon insertion and an in-frame deletion was constructed in the coding region of this gene. The resulting non-chemotactic mutant exhibited wild-type pathogenicity when injected intra-peritoneally into fish but showed a decrease in virulence similar to that seen for the non-motile aflagellate mutants following immersion infection. Hence, chemotactic motility is a required function of the flagellum for the virulence of V. anguillarum.
authors.affiliation: Department of Cell and Molecular Biology, Umeå University, Sweden.
authors.forename: R
authors.initials: R
authors.lastname: O'Toole
authors.forename: D L
authors.initials: DL
authors.lastname: Milton
authors.forename: H
authors.initials: H
authors.lastname: Wolf-Watz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002633:Chemotaxis / Q000235:genetics*; D003001:Cloning, Molecular; D004251:DNA Transposable Elements / Q000235:genetics; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology; D005407:Flagella / Q000502:physiology; D005798:Genes, Bacterial / Q000235:genetics; D008780:Methyltransferases / Q000235:genetics* / Q000502:physiology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010641:Phenotype; D051877:RNA Polymerase Sigma 54; D016415:Sequence Alignment; D012808:Sigma Factor / Q000235:genetics; D014337:Trout / Q000382:microbiology; D014733:Vibrio / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology / Q000648:ultrastructure; D014735:Vibrio Infections / Q000382:microbiology / Q000662:veterinary; D014774:Virulence / Q000235:genetics
chemical_list: D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D008780:Methyltransferases; C038706:chemotaxis methyltransferase; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54