Abstract Maciej Dobrzynski

Stochastic dynamics and optimality of single-cell signaling and gene expression

Unicellulars strive under conditions of constant random changes in their environment.  They manage because of sophisticated homeostatic mechanisms that govern compensatory responses to environmental dynamics.  Those mechanisms typically rely on sensing by two-component signal transduction and gene expression regulation.  Those key decision making processes both function at low molecule copy numbers making them prone to suffer from fluctuations which can reduce the effectiveness of the compensatory response.  We will show that fast and robust two-component signaling can already occur when this process comprises only tens of signaling molecules per cell, i.e. when it is working in a regime where fluctuations are large.  We show that the organization of two component signaling operons indicate that those systems are likely optimized for response speed.  Gene expression has been shown to occur in burst rather than a gradual fashion.  We will present a number of quantitative indices for the characterization of bursts and discuss two mechanisms that give rise to bursts.