51. Flagellin A is essential for the virulence of Vibrio anguillarum
- Author
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Ronan F. O’Toole, Per Hörstedt, Debra L. Milton, and Hans Wolf-Watz
- Subjects
Vibrio anguillarum ,Sequence analysis ,DNA Mutational Analysis ,Molecular Sequence Data ,Mutant ,Virulence ,Microbiology ,Polar mutation ,Animals ,Amino Acid Sequence ,Cloning, Molecular ,Molecular Biology ,Gene ,Vibrio ,Antigens, Bacterial ,Base Sequence ,Sequence Homology, Amino Acid ,biology ,Genetic Complementation Test ,Wild type ,Sequence Analysis, DNA ,Chromosomes, Bacterial ,biology.organism_classification ,Molecular biology ,Disease Models, Animal ,Flagella ,Genes, Bacterial ,Oncorhynchus mykiss ,Vibrio Infections ,biology.protein ,bacteria ,Flagellin ,Research Article - Abstract
A flagellin gene from the fish pathogen Vibrio anguillarum was cloned, sequenced, and mutagenized. The DNA sequence suggests that the flaA gene encodes a 40.1-kDa protein and is a single transcriptional unit. A polar mutation and four in-frame deletion mutations (180 bp deleted from the 5' end of the gene, 153 bp deleted from the 3' end of the gene, a double deletion of both the 180- and 153-bp deletions, and 942 bp deleted from the entire gene) were made. Compared with the wild type, all mutants were partially motile, and a shortening of the flagellum was seen by electron microscopy. Wild-type phenotypes were regained when the mutations were transcomplemented with the flaA gene. Protein analysis indicated that the flaA gene corresponds to a 40-kDa protein and that the flagellum consists of three additional flagellin proteins with molecular masses of 41, 42, and 45 kDa. N-terminal sequence analysis confirmed that the additional proteins were flagellins with N termini that are 82 to 88% identical to the N terminus of FlaA. Virulence studies showed that the N terminal deletion, the double deletion, and the 942-bp deletion increased the 50% lethal dose between 70- and 700-fold via immersion infection, whereas infection via intraperitoneal injection showed no loss in virulence. In contrast, the polar mutant and the carboxy-terminal deletion mutant showed approximately a 10(4)-fold increase in the 50% lethal dose by both immersion and intraperitoneal infection. In summary, FlaA is needed for crossing the fish integument and may play a role in virulence after invasion of the host.
- Published
- 1996