Fig 2. A simple spatial model of T6S-driven community dynamics.

(a) Any cell can divide. Division results in an identical cell being placed in an adjacent site. If no adjacent site is available, cells are pushed out of the way to make room for the new cell (S1 Text). (b) T6S+ cells (red) can attack any cell. When a sensitive cell (blue) is attacked, it is “killed” (removed from the system). T6S+ strains are self-immune. (c-f) Time series of competitions between a T6S+ strain (red) and a sensitive strain (blue) during a range expansion in 2D. In all cases the T6S+ growth rate is α _t = 1, and the sensitive strain growth rate is α _s = 4. Initial sensitive strain fractions are 0.1 (c, d) and 0.5 (e, f). Attack rates are γ = 5 (c, e) and 15 (d, f). (g) Quantification of dynamics observed in panels (c-f). Thin colored lines are individual trajectories; dotted black lines are averages over 8 of the 10 cases shown (eliminating highest and lowest outliers). Parameters are as in the time series. Time is units of 1/α _t. Timestep multiplier λ = 1.