(A) Regions from which the samples were taken at the end of the experiments of Figure 5. The three rows show the replicates highlighted with gray, purple, and green arrows in Figure 5B, respectively. Different columns show the same populations at every other transfer. The scale bar is 1 cm long. (B) Density histograms of fluorescence intensity (y axis, arbitrary units) versus forward scatter (FSC, x axis, arbitrary units), which correlates with cell size, measured via flow cytometry during competitions in well-mixed liquid cultures between strains K1, K1o, and K1s, versus K2b. K1 is the strain used in all other experiments, K1o and K1s are populations sampled at end of the experiments of Figure 5. The fluorescence intensity of population K1o is lower than that of K1 and K1s. The dashed line shows the K1 histogram mode as a visual aid to compare fluorescent intensities. (C) In competition assays in liquid at 360 µM galactose, the frequency of K1 and K1s competing against strain K2b increases faster than the frequency of K1° competing against K2b, showing that population K1o is a weaker killer than K1 and of other populations that successfully expanded in the experiments of Figure 5 (e.g., K1s). (D) In competition assays in liquid at 360 µm galactose, strain K1 competing against strain K2b (cyan) and strain K1 against the sub-population K2bo (light blue) sampled at the end of the experiment of Figure 5 follow similar dynamics suggesting that the collapse of K1o was not due to increased toxin production by K2bo, or it developing resistance to the K1 toxin. The competition assay with strain K1 against strain K2br (green), which re-invaded a K1 population in the experiments of Figure 5, instead, showed no increase in frequency for strain K1, suggesting that K2br developed resistance to the K1 toxin. Different data points in (C–D) show different technical replicates.