ANALYSIS OF MOTION OF BACTERIA WITH ROTATING FLAGELLA

A method is proposed for analyzing the swimming motions of bacteria. I t is assumed that a bacterium consists of a spherical cell body and se veral rotating flagella. The forces and torques exerted on each flagel lum are evaluated in a coordinate system fixed to the flagellum, using the resistive force theory. They are transformed into a coordinate sy stem fixed to the cell body. Then, the velocity and angular velocity o f the cell body can be determined because the net force and torque on the bacterium are zero. This method is applicable to the motion of bac teria with rotating flagella in any form of curve attached at any poin t on the cell body. A numerical example shows that the trajectory of b acteria with a flagellum slanting from the radial direction of the cel l body follows the pattern of a double helix. Another example shows th at a doubly flagellated bacterium swims faster than a singly flagellat ed bacterium.