Polar flagellar motility of the Vibrionaceae

Polar flagella of Vibrio species can rotate at speeds as high as 100,000 rp m and effectively propel the bacteria in liquid as fast as 60 mum/s. The so dium motive force powers rotation of the filament, which acts as a propelle r. The filament is complex, composed of multiple subunits, and sheathed by an extension of the cell outer membrane. The regulatory circuitry controlli ng expression of the polar flagellar genes of members of the Vibrionaceae i s different fi-om the peritrichous system of enteric bacteria or the polar system of Caulobacter crescentus. The scheme of gene control is also pertin ent to other members of the gamma purple bacteria, in particular to Pseudom onas species. This review uses the framework of the polar flagellar system of Vibrio parahaemolyticus to provide a synthesis of what is known about po lar motility systems of the Vibrionaceae. In addition to its propulsive rol e, the single polar flagellum of V. parahaemolyticus is believed to act as a tactile sensor controlling surface-induced gene expression. Under conditi ons that impede rotation of the polar flagellum, an alternate, lateral flag ellar motility system is induced that enables movement through viscous envi ronments and over surfaces. Although the dual flagellar systems possess no shared structural components and although distinct type III secretion syste ms direct the simultaneous placement and assembly of polar and lateral orga nelles, movement is coordinated by shared chemotaxis machinery.