Inducers of HpaR protein. (A) SDS–PAGE analysis of the phenyl-Sepharose chromatography of HpaR. Lane P, molecular mass markers shown in kDa; lanes 1–8, fractions eluted with 4HPA (lane 1), 2HPA (lane 2), 3HPA (lane 3), 3,4HPA (lane 4), PP (lane 5), PA (lane 6), 3-hydroxycinnamic acid (lane 7) and 2,5HPA (lane 8). (B) Effect of several aromatic compounds on the expression of Pg promoter. Cells of E.coli WPG11 (Pg::lacZ) were grown in glycerol-containing minimal medium in the absence (no aromatic) or in the presence of 1 mM different aromatics (4HPA, PA, 2HPA, 3HPA, PP, 2,5HPA, 3,4HPA and 3-hydroxycinnamic acid) until the cultures reached an OD600 of 0.8. β-Galactosidase activities were measured with permeabilized cells as described in Materials and Methods.