FIG. 2.
Efflux of the fluorophore DMP from various mutant strains. The indicated strains were pregrown in M9 medium containing 1% thiamine and 0.2% Casamino Acids and then were washed and adjusted to an optical density (600 nm) of 0.1. At 0 min, DMP was added to a final concentration of 25 μM, and fluorescence was immediately recorded. The strains used were as follows: PAO1, wild type expressing MexAB-OprM; PAO238-1, a mexL mutant expressing MexJK; and PAO314 Δ(mexJKL), expressing no efflux system. Strains containing pPS1180 express OprM.