Fig. 5.

The behavior of AglR molecules is sensitive to the hardness of the gliding surfaces. (A) On 1.5% agar, most AglR molecules show displacement during 1.2 s. On 5% agar, where most motors are engaged in exerting force against the cell envelope, bigger population of AglR is observed nonmotile. The image of one frame (red, Left) is merged with a frame recorded 0.3 s later (green; Center). The motion of AglR molecules during each 0.3-s interval is shown as the color shifts in the merged images (Right). The outline of each cell is shown in the first frame. (Scale bar, 1 µm.) In a time period of 1.2 s, no cell movement was detected. (B) As the surface hardness increases or the cells are embedded in 1.5% agar, the probability of AglR moving with high velocities (>800 nm/s) decreases. (C) On 0.8%, 1.5%, and 5.0% agar, the V_2D-max of AglR molecules is similar, whereas the V_2D-avg decreases dramatically as the surface hardness increases. When cells are embedded in 1.5% agar, both V_2D-max and average V_2D decrease. These results indicate that AglR molecules slow down more frequently when they contact with harder or broader gliding surfaces.