Speaker: Professor Chuan Xue from Department of Mathematics, Ohio State University

Title: The Role of Intracellular Signaling in the Stripe Formation in Engineered E. Coli Populations

Abstract: Recent experiments showed that engineered Escherichia coli colonies grow and self-organize into periodic stripes with high and low cell densities in semi-solid agar. The stripes establish sequentially behind a radially propagating colony front, similar to the formation of many other periodic patterns in nature. These bacteria were created by genetically coupling the intracellular chemotaxis pathway of wild-type cells with a quorum sensing module through the chemotaxis protein CheZ. In this paper, we developed multiscale models to investigate how the intracellular pathway affects the stripe formation. We first developed a detailed hybrid model that treats each cell as an individual particle and incorporates intracellular signaling via an internal ODE system. To overcome the computational cost of the hybrid model due to the large number of cells involved, we next derived a mean-field PDE model from the hybrid model using asymptotic analysis. The analysis is justified by the tight agreement between the PDE model and the hybrid model in 1D simulations. Numerical simulations of the PDE model in 2D with radial symmetry agree with experimental data semi-quantitatively. Finally, we used the PDE model to make a number of testable predictions on how the stripe patterns depend on cell-level parameters, including cell speed, cell doubling time and the turn-over rate of intracellular CheZ. (Joint work with Min Tang and Xiaoru Xue)