Bacterial growth control and the control by bacterial growth

From Q-bio

Bacteria take on a broad range of sizes and macroscopic compositions at different growth rates, describable by a number of universal growth laws as discovered by Schaecter et al 50 years ago. These growth laws take on a special significance at the dawn of quantitative systems biology: On the one hand, growth rate affects almost every quantity one may wish to quantify in a microbe, in particular, transcriptional and translational processes that control the degrees of gene expression. I argue that growth-rate dependent effects must be taken into account for the robust operation of both endogenous and synthetic genetic circuits. On the other hand, a quantitative understanding of the growth laws will be a grand example of what quantitative biology aims to establish, a quantitative link from molecules to physiology. Here I will describe a coarse-grained model that incorporates essential ingredients of metabolism and growth in the simplest way, focusing on the partitioning of ribosomal and non-ribosomal proteins. The model can describe all available data (those from our lab and from others dating back 30 years ago for a variety of strains of E. coli) by 1-2 fitting parameters. Experiments to test the model by growing E. coli cultures under a variety of growth-limiting conditions revealed remarkable simplicity in the strategy of growth control.