aeruginosa. Figure 6 A model for QS regulation MAPK inhibitor mechanism via the RND-type efflux pump MexAB-OprM . (a) MexAB-OprM extrudes 3-oxo-Cn-HSLs and controls the accessibility of non-cognate acyl-HSLs to LasR in P. aeruginosa QS-regulation. (b) In the P. aeruginosa MexAB-OprM mutant, non-cognate 3-oxo-Cn-HSLs activate LasR. Non-cognate 3-oxo-Cn-HSLs-LasR complexes induce the wrong QS regulation. Methods Bacterial strains, plasmids and

growth conditions The bacterial strains and plasmids used in this study are listed in Table 1. Bacterial cells were grown in LB broth or on LB agar at TH-302 chemical structure 37°C or 30°C. The following antibiotics were added to media at the indicated concentrations: ampicillin, 100 μg/ml for E. coli; carbenicillin, 200 μg/ml for P. aeruginosa; tetracycline, 25 μg/ml for E. coli, 100 μg/ml for P. aeruginosa. Table 1 Strains and Plasmids Strains/Plasmids Characteristics Reference Strains     P. aeruginosa     PAO1

ATCC15692 [29] KG4509 ΔmexB derivative of PAO1 This study KG7004 ΔlasI ΔrhlI derivative of PAO1 This study KG7050 ΔlasI ΔrhlI ΔmexB derivative of PAO1 This study KG7403 gfp fused to the lasB promoter and integrated at the attB site of the KG7004 chromosome This study KG7503 gfp fused to the lasB promoter and integrated at the attB site of the KG7050 chromosome This study E. coli     DH5α F-, Φ80d lacZ ΔM15, Δ(lacZYA- argF’)U169, deoR, recA1, endA1, hsdR17(rk – mk +), phoA, supE44,

λ-, thi-1, gyrA96, relA1 [30] S17-1 RE42-Tc: Mu-Km:: Tn7 pro res mod4 [31] Plasmids     pUC18 Apr; high-copy-number cloning vector [32] pBR322 Apr Tcr; high-copy-number cloning vector [33] pSL1180 super-polylinker phagemid [34] pTO003 Gmr; E. coli-P. aeruginosa shuttle expression vector [35] pMT5059 Cbr; pBend2 derivative carrying multiple-cloning 4��8C site and Not I site [36] pMT5071 Cmr; pMOB3 derivative carrying Ω-Cm instead of Cm [37] pAF2071 Cbr Cmr; pKT5059 carrying 2911-bp fragment with 3′ flanking region of rhlI including 91-bp of rhlI and 2110-bp fragment with 5′ flanking region of rhlI Mob cassette from pMT5071 at Not I This study plasI Cbr Cmr; pMT5059 carrying 1.0-kb PCR fragments with 3′ and 5′ flanking regions of lasI and Mob cassette from pMT5071 at Not I This study pMexB Cbr Cmr; pMT5059 carrying 1.