Figure 3.

Analysis of growth in LB for PAO1, ΔmexL, and ΔmexK strains in (A) absence and in (B–D) presence of antimicrobials. Growth (OD₆₀₀) was measured for 24 h in the presence of compounds suggested to be MexJK substrates—(B) erythromycin and (C) triclosan—as well as in the presence of one antibiotic that has not been proved to be related to MexJK—(D) ciprofloxacin. The concentrations of the antimicrobials used were 64 μg/mL erythromycin, 0.06 μg/mL ciprofloxacin, and 109 μg/mL triclosan. Error bars indicate standard deviations for the results from three independent replicates. As shown, neither the absence nor the overexpression of mexJK produced any relevant effect on P. aeruginosa growth under the tested conditions. These data indicate that mexJK overexpression or the lack of this efflux pump does not produce a relevant effect on P. aeruginosa fitness and reinforce the idea that mexJK does not contribute to erythromycin, ciprofloxacin, or triclosan resistance in a wild-type genomic context.