Figure 3. Population-level and single-cell level growth analysis.

(A) Birth length $l_{\text{b}}$ plotted against division length $l_{\text{d}}$ for all measured cells, together with a linear fit (blue line), which has a slope of 0.91±0.16. Gray solid line: best fit assuming a pure sizer (slope 0). Gray dashed line: best fit assuming a pure adder (slope 1). The 95% confidence intervals of the linear fit, obtained via bootstrapping, are indicated by the blue shaded region. (B) Generation time versus ${\displaystyle \mathrm{l}\mathrm{n}\left(\frac{l_{\text{d}}}{l_{\text{b}}}\right)}$ for all cells (blue dots) and the average per generation time (orange squares), with the standard error of the mean shown for all generation times for which at least three data points are available. The orange line represents a linear fit through the generation time averages that passes through the origin. For exponential growth, the averages would lie along this line, and the slope would be equal to the exponential growth rate. (C) Growth trajectory for a single cell (upper panel), together with its derivative for each measurement interval (lower panel). Fits to the derivative are shown for linear growth (black dash-dotted line) and exponential growth (red dashed line).