Fig. 2.

Migrating fronts of P. mirabilis swarms. (A) Bimodal expression of the pKG100 idsA-gfp fusion in cells of P. mirabilis at the outer edge of a swarm. The phase image is shown on the left, the fluorescence image is in the center, and the false-colored image is on the right and shows the agar background in red, fluorescence bright cells in green, and dark cells in black. Asterisks mark examples of dark cells, and arrowheads indicate swarm tracks. (B) Control. Outer swarm edge of BB2000 cells carrying a chromosomally integrated constitutive gfp (10). Asterisks mark dim cells (dark cells were not evident), and arrowheads indicate swarm tracks. The marker bars shown are 50 μm.