Figure 7. Distinct Behavioral Regimes Emerge from RBS Modification.

(A) The gene circuit topology from Fig. 6A was further modified with an additional, orthogonal operon containing the P_lux-λ promoter driving polycistronic expression of GFP, mCherry, and critically, cI, the repressor from λ bacteriophage. In addition to being activated by AHL, this promoter is also repressed by cI, thus the new operon is auto-repressing. Furthermore, the robot is programmed to inject AHL into the living, onboard microbiome when it nears any carbon depot. (B) When the simulated RBS strength for cI (RBScI) is close to 0.0, the robotic platform behaves in the stalk-pause-strike manner described in Fig. 6.(C) With the RBScI value at 0.0007, there is a decrease in the length of the ‘strike’ period of the predation pattern leading to a stalk-pause-strike-pause-stalk behavioral regime. (D) Increasing the RBScI value to close to 0.01 leads to a regime of inactivity whereby the robotic platform is unable to acquire even one carbon depot. (E) Finally, as the RBScI value approaches 1, the system behaves similarly to the initial balanced toggle switch seen in Fig. 3. These multiple, and strikingly different, host behavioral regimes indicate how biochemical networks of the microbiome may have drastic impacts on host behavior.