FIG. 1.

Intracellular accumulation of levofloxacin with or without addition of NMP, mTFMPP, PAβN, and CCCP in the acrAB-overexpressing E. coli strain 3-AG100MKX. Levofloxacin (10 μg/ml) was added at time point 0, and NMP, mTFMPP, PAβN, or CCCP were added after 10 min. Samples removed at timed intervals were centrifuged through silicone oil, and the pellet was resuspended in 0.1 M glycine hydrochloride (pH 3.0). After overnight incubation at room temperature, samples were again centrifuged, and the amount of released levofloxacin in the supernatant was determined spectrofluorometrically. Shown are representative results from one out of three experiments.