Fig 1.

BrlR-dependent expression of the multidrug efflux pumps MexAB-oprM and MexEF-OprN. (A) Expression levels of efflux genes mexA and mexE are BrlR dependent. mexA and mexE transcripts were quantified by real-time qRT-PCR in the ΔbrlR mutant and PAO1/pJN-brlR. Relative transcript levels were based on comparison to PAO1. (B) No difference in mexA and mexE transcript levels are noted under planktonic growth conditions upon inactivation of brlR compared to the wild type. (C) Abundance of MexA in wild-type biofilms (PAO1) and strains inactivated in or overexpressing brlR (ΔbrlR mutant and PAO1/pJN-brlR) as determined by immunoblot analysis using 5 μg of the periplasmic protein fraction and anti-MexA antibody. Lane M, protein marker. (D) Quantitative analysis of MexA levels in ΔbrlR mutant and PAO1/pJN-brlR biofilms relative to P. aeruginosa PAO1 biofilms. *, significantly different from the values for P. aeruginosa PAO1 (P ≤ 0.01). Experiments were carried out at least in triplicate. Error bars denote standard deviations.