Fig. 2: 2-Tits-for-tat (2TFT) outperforms tit-for-tat (TFT) vs. a (R)andom firing strategy.

a Model representation of retaliatory T6SS firing in response to a random attacker (R, blue). Following R’s initial attack (t₁), the retaliator cell (TFT, yellow) fires T6SS needles outwards from the points on its surface where initial attacks struck (t₂, magnified box). b Simulation snapshots showing initial and final cell configurations for competitions between R and TFT strategists (“low” and “high” initial cell populations correspond to 10 vs. 10 and 200 vs. 200 cells as in Fig. 1). c Competition outcome, measured by final R cell proportion, as a function of firing rate k_fire,R for increasing initial cell densities (see legend, right). Circles and lines correspond to data points and their means, respectively. d Invasion plots showing outcomes of local and global invasion analyses for R vs. TFT competition, as a function of firing rate, k_fire,R, for high initial cell density (200 vs. 200 cells). e–g Analogous to b–d, except with TFT replaced by 2TFT, which counterattacks twice per successful oncoming attack. Simulation parameters: N_hits = 2, c = 0.001. n = 5 simulation replicates per case in c, d, f, and g. Source data are provided as a Source Data file.