Bacterial physiology has traditionally been studied on the population level. However, novel single-cell experiments reveal that there is significant cell-to-cell variation in quantities like growth rate, gene expression, intracellular metabolite concentrations, energy levels, etc., that are stochastic but presumably not completely independent. Here, we study these variations using biophysics, single-cell microscopy, genetics, and modeling. By identifying constraints of variations and cross-correlations between different quantities we establish possible modes of regulation.
An important physiological quantity we are interested in is cell volume. Together with the amount of intracellular proteins and other biopolymers volume determines the level of intra-cellular molecular crowding, which in turn has strong implications for molecular processes such as enzymatic rates or protein mobility. Here, we study how cell volume, crowding, and other physiological processes are co-regulated.
Figure: High-speed centrifugation of different E. coli mutant strains and drug-treated cells in percoll density gradients reveals their distributions of intra-cellular mass densities.