Dresden 2009 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 17: Poster II
BP 17.24: Poster
Mittwoch, 25. März 2009, 17:15–19:45, P3
Phenotype Decision in B. subtilis: Low Number Fluctuations Enhanced by Non-linear Dynamics — •Jan-Timm Kuhr1,3, Madeleine Leisner2,3, Joachim O. Rädler3, Berenike Maier2,3, and Erwin Frey1,3 — 1Arnold Sommerfeld Center for Theoretical Physics (ASC) and Center for NanoScience (CeNS), LMU, Germany — 2Institut für Allgemeine Zoologie und Genetik, Westfälische Wilhelms Universität, Germany — 3Department für Physik, Ludwig-Maximilians-Universität München, Germany
Clonal populations of the bacterium B. subtilis exhibit a variety of phenotypes, depending on the environment. If starved 15-20% of all cells become “competent”, gaining the ability to incorporate external DNA into their genome. Competent individuals can adapt quicker to stress conditions than the residual population. Whether to become competent or not is decided on the single cell level.
To elucidate switching to competence we performed single cell experiments and set up a theoretical model incorporating non-linear feedback dynamics and low number fluctuations. Identifying the master regulator protein comK and its corresponding mRNA as the main players, we can describe switching by an effective two-species system: switching is induced by fluctuations and subsequent relaxation to one of two stable fixed points. Deterministic switching, as encountered in mutant strains, is easily explained by disappearance of one fixed point.
Using well-motivated rate constants we quantitatively reproduce our experimental results and give an intuitive picture of stochastic single cell phenotype decision.