Figure 1.

PolC stoichiometry within each cell and at each replisome. (a) Representative fluorescence image of wt B. subtilis cells (upper) and cells with PolC-mCherry (lower). PolC-mCherry foci are highlighted by yellow arrows. (b) Distribution of initial total cellular fluorescence intensity for wt cells (median = 1.43 × 10⁶) and cells labeled with PolC-mCherry (median = 2.77 × 10⁶). The difference in fluorescence indicates the total intensity of mCherry in labeled cells. (c) Representative background-subtracted intensity time traces (gray lines) of two different PolC-mCherry foci undergoing photobleaching, where different intensity states (black lines) are identified by maximum likelihood estimation. The left panel shows typical, fairly uniform steps, whereas the right panel shows a scenario where multiple photobleaching events occurred within a single frame. (d) Distribution of PolC copy numbers at each PolC-mCherry focus. The black line is a guide to the eye. To see this figure in color, go online.