Figure 1

Gene networks used in this work. The three main transcriptional regulatory cascades are illustrated. A-C) Genetic circuit structure. The underlying inducible and repressible mechanisms are reported: in the presence of LuxR, 3OC₆-HSL activates Plux; TetR and LacI, encoded by the tetR and lacI genes, respectively, repress Ptet and Plac; the A protein, encoded by the A gene, activates PA. Curved arrows represent promoters, straight arrows represent genes, ovals represent RBSs and octagons represent transcriptional terminators. Pcon is a constitutive promoter. D-H) Block schemes for the genetic circuits, where, for each module, the steady-state transfer function is qualitatively described by reporting its input-output trend. Module 1 is the LuxR/Plux-based 3OC₆-HSL-inducible device (panels D-H); Module 2 is TetR/Ptet NOT gate in panels D, E, H, while it is the YES gate in panels F, G; for some experiments reported in the Results section, the TetR/Ptet NOT gate was replaced by a LacI/Plac NOT gate, which has the same repressible logic and this configuration is not shown in this figure; Module 3 is the LacI/Plac NOT gate (panel H). Noise is applied to the output of Module OUTPUT₁ (panels D, F) or to both OUTPUT₁ and OUTPUT₂ (panels E, G, H).