Figure 1.

The design of the switch system. (A) In the absence of Stl-binding to its recognition sequence, lacZ can be expressed in the cell, leading to blue colonies in the experimental setup. The exact sequence from the SaPI_bov1 genome (13733–13933) cloned into the lacZ promoter is shown. Specific Stl binding sites are labeled with green, conserved sites are shown with capital letters; (B) Stl binding to the promoter inhibits lacZ expression, leading to white colonies in the experimental setup; (C) The phage dUTPase protein sequestrates Stl^WT from the promoter DNA segment, leading to blue colonies.