Figure 1

Cells swim in clockwise, circular trajectories at solid, planar surfaces. When a cell executes a "run", all flagella in the bundle rotate anticlockwise (when viewed from behind) and the cell body counter-rotates in a clockwise direction. When viewed from above, the cell trajectories at the bottom surface appear clockwise and the cell trajectories at the top surface appear anticlockwise (image and text: Nature 435 1271).