Fig 4.

Expression of mexAB-oprM or mexEF-oprN partially restores ΔbrlR susceptibility to antimicrobial agents. Biofilms of P. aeruginosa PAO1, the ΔbrlR mutant, and the ΔbrlR mutant overexpressing mexAB-oprM or mexEF-oprN were grown for 1 day and subsequently treated for 1 h with tobramycin (150 μg/ml) (A), kanamycin (150 μg/ml) (B), trimethoprim (150 μg/ml) and tetracycline (100 μg/ml) (C), and norfloxacin (400 μg/ml) (D). Biofilms of P. aeruginosa PAO1, the ΔbrlR mutant, and the ΔbrlR mutant coexpressing both mexAB-oprM and mexEF-oprN were grown for 1 day and subsequently treated for 1 h with tobramycin (150 μg/ml) (E) and norfloxacin (400 μg/ml) (F). P. aeruginosa PAO1 isolates harboring empty vectors (pMJT1 and pJN105) were used as controls. Experiments were carried out at least five times. Error bars denote standard deviations. * and **, significantly different from the values for P. aeruginosa PAO1 (P ≤ 0.05 and P ≤ 0.01, respectively).