Cinemicrographic analysis of the movement of flagellated bacteria. II. The ratio of the propulsive velocity to the frequency of the wave propagation along flagellar tail.

We took cinemicrographs of the movement of the flagellar tail of the peritrichously flagellated bacterium, Salmonella, swimming in a medium containing methylcellulose under a dark-ground microscope. By analysing the film, the velocity of translation u, the frequency of the propagation of helical waves along the tail fF and the frequency of the induced rotation of bacterial body fB of individual organism were measured and the experimental values of the ratios u/fF, u/fB and fF/fB were obtained. On the other hand, the theoretical values of these ratios were calculated by inserting the geometrical parameters describing the shapes and the sizes of the body and the tail of individual organism into the equations previously derived for the hydrodynamic model of the propulsion of flagellated bacteria (Holwill and Burge, 1963; Chwang and Wu, 1971). For four bacterial specimens presently analysed, the experimental values of u/fF ranged from 0.5 to 0.9, whereas the theoretical values were about 0.3. As reported by the preceding paper, such a tendency for the experimental values to exceed the theoretical ones by two or three times was also seen in u/fB and, consequently, the experimental and the theoretical values of fF/fB showed good agreement. From the results of these quantitative analyses of the movements of flagellated bacteria, it was concluded that the validity of the hydrodynamic model was further supported experimentally.