AHL quorum-sensing regulation is required for trehalose accumulation and increased treZ and osmC transcripts in response to ethanol. (A and B) Expression of treZ (A) and osmC (B) genes normalized to rpoD in PA14 wild-type and ΔlasR ΔrhlR strains in buffered LB with and without 1% ethanol for 16 h. (C) Trehalose quantification of PA14 wild-type and ΔlasR ΔrhlR cells grown planktonically in M63 medium with and without 1% ethanol for 16 h. (D) β-Galactosidase assay of rhlI-lacZ promoter activity in PA14 wild-type and ΔlasR ΔrhlR cells grown planktonically in M63 medium with and without 1% ethanol for 16 h. The data are representative of the results of at least 2 independent experiments, each with 3 or more biological replicates. The statistics are based on two-way ANOVA and Tukey’s multiple-comparison test. (A) a-b, a-d, b-c, and b-d, P < 0.0001; a-c, P = 0.0004; c-d, P = 0.0395. (B) a-b and b-c, P < 0.0001; a-c, P < 0.02. (C) a-b, P = 0.0002. The error bars indicate standard deviations.