FIG 1.
Tobramycin resistance of ΔlasR mutants is strain dependent. (A) The MIC of tobramycin was determined for each strain carrying intact lasR (LasR+, black bars) or ΔlasR (LasR−, white bars). The significance of the effect of strain (wild type, T1, or T3) and lasR allele (LasR+ or LasR−) and the interaction of the two on MIC was determined by two-way ANOVA by performing pairwise comparisons of each LasR+/− strain pair with that of PA14. The interaction was significant for T1 (F1,8 = 156.8 and P < 0.0001) and T3 (F1,8 = 10.67 and P < 0.05). Pairwise comparisons of LasR+ and LasR− of each strain were determined using Sidak’s post hoc test with P-values adjusted for multiple comparisons; *, P < 0.05; ****, P < 0.0001; ns, not significant. (B) Tobramycin MIC of T1 and T1-mutated strains. Where indicated, AHL (3OC12-HSL) was added before inoculating culture tubes at the 10-μM final concentration. Statistical analysis was done by one-way ANOVA and Dunett’s multiple comparisons with T1; **, P < 0.01. For panels A and B, results are the average of three independent experiments and the vertical bars indicate standard deviation.