The polar flagellar motor of Vibrio cholerae is driven by an Na+ motive force

Abstract

Vibrio cholerae is a highly motile bacterium which possesses a single polar flagellum as a locomotion organelle. Motility is thought to be an important factor for the virulence of V. cholerae. The genome sequencing project of this organism is in progress, and the genes that are highly homologous to the essential genes of the Na+-driven polar flagellar motor of Vibrio alginolyticus were found in the genome database of V. cholerae. The energy source of its flagellar motor was investigated. We examined the Na+ dependence and the sensitivity to the Na+ motor-specific inhibitor of the motility of the V. cholerae strains and present the evidence that the polar flagellar motor of V. cholerae is driven by an Na+ motive force.

FIG. 1

Swarming abilities of V. cholerae strains. Fresh single colonies of the indicated V. cholerae strains were inoculated onto an LB semisolid plate (0.3% agar) and incubated for 4 h at 37°C.

FIG. 2

Na⁺-dependent and phenamil-sensitive motility of V. cholerae 1854. V. cholerae 1854 and V. alginolyticus VIO5 cells were cultured in LB or VPG medium, respectively. At late log phase, cells were harvested and resuspended in TMN medium containing various concentrations of NaCl (A) or in TMN medium (pH 7.5) containing 50 mM NaCl, 50 mM KCl, and various concentrations of phenamil (B). In the experiment shown in panel A, the total concentration of salts in TMN medium was adjusted to 100 mM by the addition of KCl. The swimming speeds of the cells were obtained as described in Table 1, footnote c.