Executive Summary : | An E.coli cell shows motile response to chemical gradient present in its environment. Using its run-tumble motion the cell can migrate towards a favorable region with higher (lower) concentration of attractant (repellant) chemical. This motion is known as chemotaxis. It is important to understand how chemotactic performance is affected by changes in extra-cellular and intra-cellular conditions. Although this question has received significant research attention in recent past, a complete understanding is not yet reached. In this project we propose to use a detailed theoretical model to describe intra-cellular signaling pathway and perform numerical simulations to explain the cell behavior. In particular, we plan to quantitatively characterize performance in terms of (a) how fast the cell can migrate towards favorable region, (b) how efficiently the cell is able to localize in the favorable region, and in general (c) how well the cell can differentiate between a favorable and hostile environment. We propose to investigate how each of these performance criteria depends on changes in extra-cellular and intra-cellular environments. Two types of changes are possible: systematic and stochastic. We are interested to study the effect of stochastic fluctuations present in the signaling network, and systematic spatio-temporal variation in extra-cellular chemical environment. Our study will unravel how the interplay between the complex signaling network inside the cell and dynamical ligand environment outside the cell results in highly non-trivial cell behavior. |