Movie S1.

TFP-deficient (∆pilA) (green) cells dominate the swarm edges throughout swarm growth, while wild-type (WT) (red) cells remain localized near the swarm center. The upper left assay was inoculated with wild-type cells, the upper right with ∆pilA cells, the lower left with a 1:1 ratio of ∆pilA:WT cells, and the lower right with a 1:10 ratio of ∆pilA:WT cells. The diameter of each assay plate is 60 mm. Frames were captured once every 10 min for 24 h—playback is 10 frames per second (i.e., movie is 6000× acquisition speed).