Figure 1. Evolved StLT2 cells inhibit the growth of ancestral cells.

A) The indicated evolved StLT2 lineages were co-cultured with the ancestral strain for 24 h in broth. Viable cell counts for each population were determined as colony forming units and these data were used to calculate the competitive index as described in Methods. Each evolved lineage was competed against ancestral cells (black bars), ancestral cells overexpressing rhsI^main (light grey bars) and ancestral cells overexpressing rhsI^orphan (white bars). Reported values represent the mean ± SEM for at least three independent experiments. B) The growth inhibition activity of evolved StLT2 requires cell-cell contact. Evolved cells were co-cultured with ancestral cells in adjacent wells of a trans-well incubation chamber. Culture chambers were separated by membranes containing 0.4 µm or 8 µm pores as indicated. Reported competitive indices represent the mean ± SEM for three independent experiments.