Regensburg 2007 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 9: Regulation and Signaling
BP 9.3: Vortrag
Dienstag, 27. März 2007, 10:45–11:00, H43
Basal promoter activity of comK sets a switching-window into the K-state of Bacillus subtilis — •Madeleine Leisner1,2, Joachim Rädler1, and Berenike Maier2 — 1LMU, Department für Physik, LS Rädler, Geschwister-Scholl-Platz 1, Munic, Germany, — 2WWU, Institut für allgemeine Zoologie und Genetik, Am Schlossplatz 5, Münster, Germany
Bacillus subtilis cell population divides into a competent fraction and a non-competent fraction in the stationary phase. The transition from the non-competent state (with basal ComK concentration) to the K-state (with high ComK concentration) behaves like a bistable switch. To determine factors that set the fraction of cells that switch into the K-state (K-fraction), we characterized the basal comK expression in individual non-competent cells and found a broad Gaussian distribution whose center shifted towards higher values before entry into stationary phase. Basal promoter activity increased exponentially, reached a maximum and decreased towards zero in the stationary phase. The intrinsic switching rate increased and decreased with a time lag. When switching was induced prematurely by down-regulation of ComK proteolysis, the K-fraction increased strongly. Our data supports a model in which the basal ComK concentration increases during the exponential phase and the fraction at the high end triggers the autocatalytic feedback for ComK transcription. Shut-down of basal promoter activity sets a 'time-window' for switching and is thus involved in determining the K-fraction in the bimodal population.