Figure 1.

Rotational behavior of multiple flagellar motors and intracellular localization of GFP-CheW. (A) Schematic diagram of the measurement system. The cell was stuck to a coverslip, and polystyrene beads (ϕ = 0.5 μm) were attached to the sticky flagellar stubs. The phase-contrast image of each bead was recorded with a high-speed CCD camera (1250 frames/s). By calculating the angular velocity from the position of each bead, the rotational speed and direction could be estimated. A blue laser beam was focused on the back focal plane of the objective lens to excite the GFP-CheW. (B) Phase-contrast image of the cells and beads (left) and fluorescence image of the cells (right). Bar, 1.0 μm. The yellow-dotted ellipses indicate the cell bodies, motors 1 and 2 on the same cell, and motor 3 on a different cell. The strain used for the measurements had a wild-type cheW and a gfp-cheW gene encoded in chromosome and plasmid, respectively. Therefore, both wild-type CheW and GFP-CheW were coexpressed in this strain. (C) Rotational motions of three motors. Phase contrast images of beads were shown every 0.8 ms. The beads depicted by motors 1, 2, and, 3 correspond to the motors shown in Fig. 1B. Red points on the image of beads indicate the centers of beads every 0.8 ms.