FIG. 1.

Macroscopic stab assay for twitching motility. LB agar (1%) plates were stab inoculated with a needle to the bottom of the plate and incubated for 24 h at 37°C. The diffuse zone, the twitch zone, between the agar and the petri dish is a measure of twitching motility. The smaller, denser zone represents surface colony growth. (A) PAO1 wild type and “I” mutants. Colony 1, PAO1; colony 2, PAO-JP1 (ΔlasI); colony 3, PDO100 (ΔrhlI); colony 4, PAO-JP2 (ΔlasI rhlI). PAO-JP2 (ΔlasI rhlI), with PAI-1 and PAI-2 added to the agar at 10 μM each (B) and without PAI-1 and PAI-2 (C) was incubated for 48 h at 37°C.