FIG 3.

Flagellar motor speeds of cells treated with various CCCP concentrations. (A) At low CCCP concentrations, the motor speeds of WT cells were barely affected. (B) Cells exhibited two distinct motor speeds at 50 μM CCCP, one with a slightly reduced rotation (high PMF) and the other with no rotation (zero PMF). (C and D) At higher CCCP concentrations (≥70 μM), the motor speeds were zero in all cells. (E to H) The ΔtolC strain exhibited a uniform and gradual reduction in the motor speed at increasing CCCP concentrations. Note that, at very low PMF values where the bacterial flagellar motor operates with one stator unit, the motor can transiently stop in a step-like manner (81, 82), which can explain the purple trajectory in panel F. Motor speed measurements are laborious and time-consuming. The motor speeds of 10 to 15 cells were analyzed for each condition except for the experiment with the WT strain exposed to 100 μM CCCP (where 4 cells were analyzed).