Fig. 2.

TIRF observation of swimming trajectories of Caulobacter swarmer cells near a glass surface. (A) A schematic drawing showing the principle of TIRF observation. The cell is labeled with NanoOrange and illuminated with blue light through a FITC filter. Arrows indicate incident light totally reflected at the glass–water interface. (B) An overlay of 71 consecutive frames taken at 20 frames per second showing segments of circular trajectories. (C) A 3D plot (red) of a segment of circular trajectory and its projection on the glass surface (blue). The distance is measured from the intensity of TIRF images with an estimated penetration depth of 80 nm [see supporting information (SI) Fig. S1].