Fig. 5

Competence is simultaneously regulated by cell density, pH and antibiotic stress. a, b Predictions of the mathematical model (a) and experimental data (b) on the dependency of the time of competence initiation on inoculation density, initial pH, and antibiotic stress. The x-axis in a corresponds to the rate of CSP export in the model, r _e, which is a proxy for pH. The color scales with the time of competence initiation with more intense red corresponding to faster development of competence. Black represents no competence development. In b, each box corresponds to the average initiation time of three replicates. Both the model and the experimental data show that competence develops faster at higher pH and higher inoculation densities. c Antibiotics induce competence at pH values that repress natural competence development. d At pH values that are not repressive for competence development (pH > 7.4), competence develops faster in the presence of antibiotics. The stars indicate which conditions are plotted in c and d. The concentrations of streptomycin and HPUra are 3 µg mL⁻¹ and 0.075 µg mL⁻¹, respectively. We chose these sub-MIC concentrations to minimize the effect of antibiotic stress on growth