Combining Theory and Experiments to Understand Sugar Regulation in Bacteria

In this review we discuss the interaction between experiments and theory in understanding regulatory systems in bacterial cells, using the galactose network of E. coli as a model system to illustrate this. Initially, experiments led to a coarse-grained network view of this system, which revealed the structure of entangled negative and positive feedback loops that regulates galactose metabolism. A dynamical model, based on this network picture and in vitro experiments, indicated that one of the main regulators would have little role to play in any steady-state scenarios. The dynamical experiments this result suggested revealed the intricate timing sequence of gene expression in situations of rapidly decreasing galactose. All this information is slowly coming together to form a picture of how the different elements of the galactose regulatory system work together to regulate metabolism in the presence of fluctuating and changing food sources.