Polar and lateral flagellar motors of marine Vibrio are driven by different ion-motive forces

VARIOUS species of marine Vibrio produce two distinct types of flagella, each adapted for a different type of motility 1 . A single, sheathed polar flagellum is suited for swimming in liquid medium, and numerous unsheathed lateral flagella, which are produced only under viscous conditions, are suited for swarming over viscous surfaces 2-3 . Both types of flagella are driven by reversible motors embedded in the cytoplasmic membrane. Here we report that the energy source for the polar flagellar motor of Vibrio para-haemolyticus is the sodium-motive force, whereas the lateral flagellar motors are driven by the proton-motive force. This is evidence that two distinct types of flagella powered by different energy sources are functionally active in one cell.