Fig. 7.

Model of the oxylipin-dependent quorum sensing system (ODS). a The OdsR (oxylipin-dependent diol synthase regulator) receptor (represented as a blue square) is expressed constitutively. At low cell density in the presence of oleic acid (OA), this molecule (or an unknown derivative molecule) binds OdsR inducing a basal expression of the ODS operon, shown with a single plus symbol above the DS promoter (DSp). P. aeruginosa grown under these conditions produces a small amount of oxylipins. b When the cell density increases, the oxylipins reach a threshold concentration at which they bind to OdsR. OdsR in turn induces the expression of the DS enzymes at a higher rate than that induced by OA (shown with a triple plus symbol), creating a positive regulatory feedback that further increases the extracellular concentration of oxylipins. Subsequently, the oxylipins are sensed by other as yet unidentified secondary receptor(s) (shown as a green circle) that ultimately regulate the expression of the ODS effector genes