Anion Exchange in Bacteria: Reconstitution of Phosphate: Hexose 6-Phosphate Antiport from Streptococcus Lactis

This chapter discusses methods for measuring protonmotive force (PMF) and the motility that is the consequence of its use. The best-studied type of bacterial motility derives from the use of external flagella. The external flagellar filaments are thin helical structures that themselves perform no transduction of metabolic energy into mechanical work. They are rotated by motors at their base, and their rotation generates thrust. The motors are reversible, and it is this that permits control of behavior, as the reversal probability is controlled by the environment. It should be noted that PMF can, under some circumstances at least, play a role in controlling the “switching” of the flageilar motor. Major examples of this are aerotaxis and phototaxis, which appear to be more strictly “PMF taxis.” Another related aspect is pH taxis and certain classes of repellent-induced taxes, where perturbation of either internal or external pH is responsible for affecting motor switching.