Fig 1. Autostimulation of ComK expression is sufficient for bimodal distribution.

(A) Schematic presentation of comK regulation in wild-type cells (left panel), and the resulting induction of ComK in a cell population (right panel). (B) Schematic presentation of the artificial ComK feedback loop constructed by replacement of the comK promoter with the comG promoter and deletion of mecA, and the resulting induction of ComK in a cell population (right panel). Induction of competence gene expression (Pcom-gfp) was measured after 4 hours in stationary phase using flow cytometry and a GFP reporter fusion (data based on [7]). Binding of transcriptional regulators is indicated by open circles at the promoter region of the gene, and positive or negative action is depicted with arrows or perpendicular lines, respectively. See main text for details.