Analysis of swimming motion of peritrichous bacteria

Abstract

A model explaining nonlinearity of swimming motion of bacteria is proposed in this study. The swimming speed of peritrichous bacteria such as Salmonella is not proportional to the rotational rate of its cell body although the speed of monotrichous bacteria such as Vibrio is. This is so in spite of that the fluid flow induced by their motion must be a creeping flow and a linear relationship between the speed and the rotation rate is expected since the size of bacteria are very small. In order to resolve the enigma, we assume that each rotary motor driving flagellum has slightly different torque-rotational rate character. The directions of several motors are estimated by minimizing the difference between their characters and experimentally evaluated one under the condition that the direction of total torque coincides with experimental data.