THE BACTERIAL FLAGELLAR MOTOR

This chapter describes the structure and function of the bacterial flagellar motor. It examines the nonequilibrium thermodynamics of the motor. The chapter also compares, contrasts, and critically evaluates a selection of the various motor models. The motor responsible for the spinning motion of a single bacterial flagellum is considered one of the most intriguing of microbiological systems. The bacterial motor appears to incorporate a stator, probably anchored to the cell wall, within which, a rotor supported by a drive shaft rotating in a bearing is mounted; the drive shaft is mechanically linked through a universal joint to the propeller. Torque generation evidently occurs because of an interaction between the stator and the rotor brought about by a flow of protons or, in a few cases, sodium ions. The only locomotory organelle identified in bacteria is the flagellum. It comprise of two major parts, the filament and the basal body. The former is the external helical or corkscrew-shaped propeller responsible for producing mechanical thrust and the latter is the complex end unit attached to the cell membrane. The functional characteristics of the motor, in contrast to its structural characteristics, have many points in common with those of muscle. The analogies between speed of rotation and speed of contraction, and between torque and contractile force are described in the chapter. © 1993, Elsevier Science Publishers, B.V.