Fig. 4.

Surface pressure-area isotherm for AHLs with hydrophobic chain lengths varying from C₆ to C₁₄. Subsequently, surface pressure-area isotherms were recorded (Langmuir trough with film balance and platinum Wilhelmy plate) by compressing the surface monolayer. (Inset) Shown are the isotherms for 3OH-(slc)-HSL. For 3OH-(slc)-HSL extraction see Materials and Methods. Control, extract from strain devoid of cin locus. Trough volume, 120 ml; synthetic AHLs, 200 μl, 0.5 mM; 3OH-(slc)-HSL, 120 μl, 75-fold concentrated compared with the supernatant concentration of the producer strain. The number of molecules initially spread per trough area is reported for synthetic AHLs.