Molecular Characterization of Three Tandemly Located Flagellin Genes of .

is a motile, opportunistic pathogen. The flagellum, which is involved in swimming, swarming, adhesion, and biofilm formation, is considered a virulence factor for motile pathogens. Three flagellin genes, , , and , were identified from the sequenced genome. , , and formed an operon, and their encoding proteins shared 67-82% identity. Members of the operon were deleted individually or in combination to generate single mutants, double mutants, and a triple mutant. The contributions of the three flagellins to swimming, swarming, flagellum morphology, adhesion, and biofilm formation were assessed. The single mutants generally had a compromise in swimming and no significant defects in swarming, adhesion on biotic surfaces, and biofilm formation on abiotic surfaces. The double mutants displayed obvious defects in swimming and adhesion on abiotic and biotic surfaces. The flagellin-null mutant lost swimming ability and was compromised in adhesion and biofilm formation. All tested mutants demonstrated substantial but different flagellar morphologies, supporting that flagellin composition affects filament morphology. Bacterial swimming motility was significantly compromised under an oxidative stress condition, irrespective of flagellin composition. Collectively, the utilization of these three flagellins for filament assembly equips with flagella adapted to provide better ability in swimming, adhesion, and biofilm formation for its pathogenesis.