Fig. 4.

Penalty resulting from overexploitation defers a tragedy of the commons. The 1:1 (darkest), 1:10, or 1:100 (lightest) starting mixtures of Δcoa:LAC (A and C) or ΔcoaΔvwbp:LAC (B and D) were grown repeatedly in WLM for 18 h at 37 °C. The population from these cultures was then subjected to PBS (tones of black) or gentamicin [Δcoa:LAC (orange tones), and ΔcoaΔvwbp:LAC (red tones)] treatment and propagated through multiple days of culturing. Population ratios were assessed by enumeration of CFUs on selective agar plates. (A) Log₂-transformed Δcoa:LAC ratios and (B) ΔcoaΔvwbp:LAC ratios are plotted for each day. (C) Relative fitness (w) of the mutant for the Δcoa:LAC mixtures and (D) the ΔcoaΔvwbp:LAC mixtures. Black horizontal line at 1.0 represents where the mutants and LAC are equally fit. The relative fitness of both Δcoa and ΔcoaΔvwbp was significantly higher at the lowest start ratio in comparison with the highest start ratio for the gentamicin-treated samples (P < 0.05, two-way ANOVA with an interaction term and post hoc Tukey test; error bars denote ±SEM; n = 3 for each start ratio).