In contrast to humans, bacteria such as B. subtilis actively acquire extra-cellular DNA that they can heritably incorporate in their genomes, a phenomenon called “competence.” Competence is controlled by the central transcription factor ComK and its regulator ComS. The cellular concentration of these proteins is fine-tuned by an unusual genetic circuit. Ideally, the knowledge of how the individual molecules in this circuit interact dynamically will pave the way for precise predictions of the circuit output and ultimately, of bacterial behavior. We monitor single-DNA binding events of ComK using single-molecule fluorescence spectroscopy to quantify the mechanism, stoichiometry, and rates for the promotor binding of ComK.
Binding of a transcription factor to its promoter mapped with multiparameter single-molecule FRET.