(A) Diagram of the synthetic agr systems in Sender cells (top) and Receiver cells (bottom). The Sender cell contains the entire agr operon (P2-agrBDCA) and can thus both secrete and sense AIP, the autoinducing peptide. The Receiver cell, on the other hand, carries P2-agrCA and P3-yfp and thus can respond to AIP by expressing YFP. (B) Snapshots of Receiver cells grown on MSgg pads with 0 (-) or 100nM (+) chemically synthesized AIP. yfp expression from P3 is shown in green. (C) Mean P3-yfp fluorescence intensity from individual Receiver cells with 0 (-) or 100 nM (+) AIP (mean ± SEM, n = 78 cells, p<0.0001). (D) Dose response curve of Receiver cells to AIP (mean ± SEM, n = 2). (E) Images of Receiver cells grown on MSgg pad supplemented with 50% conditioned media from control cells (no agr system) or Sender cells. (F) Mean P3-yfp fluorescence intensity in Receiver cells grown with conditioned media from control cells or Sender (mean ± SEM, n = 97 cells, p<0.0001).