Fig. 2: Experiments show the importance of high density and high frequency for long-range weapons.

Colony competitions with P. aeruginosa PAO1 between wild-type and mutants susceptible to either CDI (short range) or pyocin R2 (tailocin, long range) inoculated from different densities (mean inoculum density 1.9 × 10³, 10⁴, 10⁵, 10⁶ CFU µl⁻¹). a, Representative microscopy images from equal-frequency (1:1) competitions after 48 h of growth. All strains express constitutive fluorescent protein genes and are false-coloured either blue (CDI attacker, top), magenta (tailocin attacker, bottom) or yellow (susceptible, top and bottom). Scale bar, 500 µm. b, Quantification of competition outcomes at the colony centre. One-way ANOVA showed that initial density and ratio significantly affected both weapons in the centre (CDI, density: P = 1.45 × 10⁻⁶, n = 80; CDI, ratio: P = 1.45 × 10⁻⁶; tailocin, density: P = 3.68 × 10⁻⁸, n = 91; tailocin, ratio: P = 5.01 × 10⁻¹⁰). c, Quantification of colony competition outcomes at the colony edge. One-way ANOVA showed that initial density and ratio significantly affected both weapons at the edge (CDI, density: P = 6.54 × 10⁻⁴, n = 80; CDI, ratio: P = 2.29 × 10⁻¹⁰; tailocin, density: P = 1.89 × 10⁻⁶, n = 92; tailocin, ratio: P = 1.43 × 10⁻⁹). For b and c, competitions were assessed via counts of CFUs. Competitive advantage assesses the fold change in the attacker strain compared with its competitor from the beginning to end of the competition. The tailocin attacker advantage in b and c has been adjusted for a disadvantage in the background genotype of the attacking strain (see Methods and Extended Data Figs. 3 and 4). Horizontal bars indicate the mean of independent biological replicates (n ≥ 6; see Supplementary Table 5 for exact values of n). Top brackets indicate a significant difference between the weapons (two-sided Welch’s t-test, P < 0.05, Benjamini–Hochberg correction for multiple testing; see Supplementary Table 5 for exact P values).