Figure 2. A simplified model for AHL-mediated gene regulation in bacteria. The genes I and R represent the genes encoding the AHL synthase and regulatory protein, respectively. In the presence of sufficient AHL signal, the R regulatory protein is activated, possibly by dimerization. The activated R regulatory protein binds to a specific binding site and stimulates (or represses) transcription initiation by RNA Polymerase holoenzyme (RNAP).