Sensitivity, feedback and noise in bacterial chemotaxis

Tom Shimizu
Berg Laboratory
Dept of Molecular and Cellular Biology
Harvard University


The relative abundance of information regarding the bacterial chemotaxis signaling pathway allows one to ask some basic questions regarding the design and physical implementation of intracellular signaling systems. How do you wire protein molecules together to get a feedback control system that is exquisitely sensitive over a wide dynamic range? How can such a system be reliably implemented in a noisy (femtolitre-scale) intracellular environment? Can such noise propagate from the level of molecules to cells to populations, and if so how? The increasing resolution of experimental investigations and theoretical models are helping us to solve these puzzles for the case of Escherichia coli cells.

In the theory lunch, I will review what is currently known about the E. coli chemotaxis pathway, outlining the above questions in more detail along the way. I will then describe a stochastic model of this pathway which I have used to simulate the effects of spatial interactions between receptors and molecular noise in the pathway. I will close by discussing how some its predictions have fared under the scrutiny of recent in vivo experiments, both at the level of populations and single cells.