Title: Quantifying localizations and dynamics in single bacterial cells
Description: Levels of macromolecules fluctuate both spatially and temporally in individual cells. Such heterogeneity could be exploited for bet hedging in uncertain environments, or be suppressed by negative feedback if perturbations are deleterious. For the master stress-response regulator in Escherichia coli, RpoS, both of these scenarios have been suggested. RpoS levels are also exceedingly low and controlled by the ClpXP protease, which reportedly displays extreme spatial heterogeneity. However, little is known quantitatively about RpoS dynamics. This is partly because no functional protein fusions exist, but also because the quantitative tools for studying fluctuations and localizations are limited, particularly ones that can be independently validated. Here I develop such methods and begin applying them to RpoS.