Figure 1.

Schematic diagram of the functional components of the monitor strain used to measure the LasR - OdDHL kinetic response. In the diagram, the LasR regulator is denoted as R and the signal molecule, OdDHL, is denoted as S. On-rate constants for each process are indicated in the figure. The lac-lasR construct ensures constitutive production of LasR at rate b₁. The regulator decays rapidly at rate λ₁ or binds another R, forming a slowly decaying dimer, R₂. When signal molecules are present, two signal molecules bind cooperatively to the dimer, which retains the slow proteolytic decay rate. The lasB-gfp(ASV) reporter fusion is used to monitor the R₂S₂ concentration and leads to induction of the reporter GFP(ASV), which matures into its measurable fluorescent form at rate k_g.