3-oxo-Cn-HSLs bind directly to LasR and the complexes are able to trigger lasB expression. Individual cultures of KG7403 (ΔlasI ΔrhlI PlasB-gfp) and KG7503 (ΔlasI ΔrhlI ΔmexB PlasB-gfp) were grown in LB medium with 5 μM 3-oxo-C9-HSL (a), 3-oxo-C10-HSL (b), or 3-oxo-C12-HSL (c) with 0, 10, 20, 50, or 100 μM patulin, respectively. Transcription of lasB was determined by measuring the fluorescence intensity (arbitrary units) depending on the amounts of green-fluorescence protein (GFP) derived from PlasB-gfp; emission at 490 nm and excitation at 510 nm. Open bars, KG7403; closed bars, KG7503. The data represent mean values of three independent experiments. Error bars represent the standard errors of the means.