Long-Term Memory in Bacterial Chemotaxis

The chemosensory system in E. coli is a paradigm for two-component signaling pathways. The receptors form the input and the flagellar motors form the output of the chemotaxis network. Receptor modification through methylation/demethylation provides a short-term memory (~ few seconds) that enables cells to make temporal comparisons of ligand concentrations, and hence to respond to chemical gradients during chemotaxis. Recent work has now identified a long-term memory (~ few minutes), enabled by stimuli-dependent structural changes in the assembly of the flagellar motor. I will discuss how we experimentally determine the output dose-response curves from the remodeling of single motors. I will then describe our theoretical model that provides a comprehensive description of the network input-output relationship at the single cell level.