FIG 2.

Tse1 is a toxic effector capable of triggering Bacillus sporulation. (A) Competition assays. Quantification of the percentage of sporulated Bsub cells during competition with different Pchl strains as attackers (Pchl and the ΔtssA, Δhcp, Δpaar, and Δtse1 mutants). (B) T6SS killing assays with E. coli as an indicator. Fluorescence signal measurements from E. coli pRL662-gfp after incubation with different Pchl strains (Pchl and the ΔtssA, Δhcp, Δpaar, and Δtse1 mutants). Images show a representative spot of each assay after 24 h of incubation. (C) Quantification of the percentage of sporulated Bsub cells after treatment with purified Tse1 for 3 h. (D) Competition assays of Pchl (functional T6SS) or the Δhcp mutant (nonfunctional T6SS) against the preys Bacillus (WT) and Bsub pDR111-tsi1 expressing the putative cognate immunity protein Tsi1 under the control of a constitutive promoter. In all represented competition assays (A, B, and D), the attacker and prey strains were cultured at a ratio of 1:1. After 24 h, Bsub cells were serially diluted and placed in LB for estimation of cell density (CFU) sporulation percentages. For all experiments, at least three biological replicates are shown, and the error bars represent SD. Statistical significance was assessed via t tests and one-way ANOVA followed by Dunnett tests using sporulation of Bsub when competing with Pchl as the control group. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant. Uncropped images of gel electrophoresis and Western blots of Tse1-tagged protein are shown in Data Set S9.