Extended Data Fig. 2: Transposition dynamics depends on how S_c and S_p are individually affected by the antibiotic treatment.

In Fig. 1, we considered the case where (1) S_c grows faster than S_p in the absence of an antibiotic and (2) the growth rate of S_c decreases fasters than does the growth rate of S_p with increasing antibiotic concentrations. These antibiotic-dose responses are described by a set of Hill terms (equation (3) in Methods section). The general trend described in Fig. 1 captured the dynamics for the experimental systems analyzed. In general, the responses of the two strains to antibiotics can be diverse. Here, numerical simulations are performed with 3 different sets of n_c and n_p values, while keeping other parameters the same as in Fig. 1. a, The growth rates of the subpopulation with chromosomal transposons (S_c) and the subpopulation with plasmid-based transposons (S_p) under different antibiotic concentrations. b, The relative growth rates (△μ) of the subpopulation with chromosomal transposons S_c) and the subpopulation with plasmid-based transposons (S_p) under different antibiotic concentrations. Here, different parameter sets generate three different trends of △μ with increasing antibiotic concentrations: (Left) △μ increases and then decreases, (Middle) △μ increases, decreases and then increases; (Right) △μ decreases, increases, and then decreases. c, Simulated dependence of the fraction of S_p on the antibiotic concentration. Overall, S_p is the dominant subpopulation in the culture above a threshold antibiotic concentration. Under some conditions (middle column), there may exist additional thresholds where the cost of carrying the transposon on the plasmid eventually outweighs its benefit.