Outer membrane exchange regulates mixed colony swarm expansion.

Column headers list relevant strain features of nonmotile DK8601 (A, C, D and F) or DW1419 (B and E) and A-motile DK8615 (A, B, D and E) or DW1415 (C and D) isogenic strain mixtures (1∶1 ratios). Top panels are 4 day old colonies (stereo micrographs). Bottom panels are colony edges of identical strain sets at higher magnification (10× phase contrast objective) taken at an earlier time point (15 hrs). Swarm expansion of the A+ strain was inhibited by a nonmotile strain in a TraA dependent manner.