We also isolated and characterized the filament–hook–basal body of the polar flagellum. The proteins in this structure were analyzed by MS. Eight internal

sequences matched with known flagellar proteins. The comparison of these sequences with the protein database from the complete genome of V. shilonii allows us to conclude that some components of the polar flagellum are encoded in two different clusters of flagellar genes, suggesting that this bacterium has a complex flagellar system, more complex possibly than other Vibrio species reported so far. Motility provides a survival advantage under a wide variety of environments, allowing bacteria to compete successfully for nutrients. Hence, microorganisms have developed a multiplicity of motility systems that allow them to move about in liquid or viscous media and over OSI-906 chemical structure surfaces. Bacteria and Archaea use flagella for locomotion. These are highly complex and efficient structures that not only propel the cell but also play an important role in biofilm formation, adhesion to surfaces and contribute to the virulence process in pathogenic species (for a review, see Kirov, 2003). The bacterial flagellum is formed by a helical filament, which is attached to the cell through a flexible joint known as the hook. The hook 17-AAG datasheet is connected to a complex structure known as the basal body that

spans the inner membrane, the cell wall and the outer membrane (for a review, see Berg, 2003). A limited number of bacteria possess dual flagellar systems, a polar flagellum for swimming in liquid medium and lateral flagella for swarming that involves translocation on solid surfaces. In various species of Gram-negative marine Vibrio such as Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio harveyi, the single-sheathed polar flagellum is constitutive whereas lateral flagella are inducible. However, this is not a general trait for the genus because Vibrio vulnificus, Vibrio anguillarum, Vibrio fisheri and Vibrio 3-oxoacyl-(acyl-carrier-protein) reductase cholerae do not possess a lateral flagellar system (for a review, see McCarter, 2001, 2004; Merino et al.,

2006). Induction of lateral flagella occurs in response to growth on surfaces or highly viscous media; this process is mediated apparently by the sodium-driven polar flagellar motor, which acts as a mechanosensor (Belas et al., 1986; McCarter et al., 1988; Kawagishi et al., 1996; Merino et al., 2006). Upon an increase in viscosity or contact with a surface, rotation of the polar flagellum is hindered and cells differentiate into swarmer cells. In some species, swarmer cells are elongated, multinucleated and hyperflagellated, such as V. parahaemolyticus, Proteus mirabilis and Serratia liquefaciens (Harshey, 1994; Eberl et al., 1999). In contrast, Aeromonas spp. and Azospirillum spp. do not show cell elongation (Merino et al., 2006). Rotation of the flagellar motor is powered by transmembrane ion gradients in V.