Effect of viscosity on swimming by the lateral and polar flagella of Vibrio alginolyticus

By using mutants of Vibrio alginolyticus with only a polar flagellum (Pof(+) Laf(-)) or only lateral flagella (Pof(-) Laf(+)), we examined the relationship between swimming speed and the viscosity of the medium for each flagellar system. Pof(+) Laf(-) cells could not swim in the high-viscosity environment (ca, 200 cP) in which Pof(-) Laf(+) cells swam at 20 mu m/s. The Pof(-) Laf(+) cells swam at about 20 mu m/s at normal viscosity (1 cP) without the viscous agent, and the speed increased to 40 mu m/s at about 5 cP and then decreased gradually as the viscosity was increased further. These results show the functional difference between polar and Lateral flagella in viscous environments.