FIG 2 .

Horizontally acquired T6SS effectors and immunity proteins are functional in the recipient strain. “Killer” strains and T6SS⁻ ΔvasK “prey” strains were mixed at a 10:1 ratio and incubated at 37°C for 3 h on membrane filters, and surviving prey CFU were counted on selective medium. Killer strains were either T6SS⁺ (gray bars) or T6SS⁻ (ΔvasK, white bars). Strains used were C6706 (recipient), 692-79 (donor), and C6706 derivatives in which either Aux1 (A1), Aux2 (A2), or both clusters (A1,2) were replaced by those of 692-79. Bars denote means ± standard deviations (n = 4 biological replicates, one representative experiment shown of two performed). T6SS⁺ genotypes with different letters (a, b, c, d) exhibited mean survival different from those of other T6SS⁺ genotypes (P < 0.05, ANOVA and Tukey’s HSD) within the same experiment (panel).