Figure 2. Both model prediction and data show increase in the noise in timing as newborn cell size increases.

(a) Model prediction for noise (coefficient of variation squared, CV²) in division time as computed numerically using equation (6). The model parameters used are: transcription rate k_m = 0.13 min⁻¹, threshold X = 65 molecules, growth rate α = 0.03 min⁻¹, and mean burst size b = 5 molecules. The distribution of protein burst size B_i is assumed to be geometric. For details on how these parameter values were estimated, see SI, section S6. (b) Experimental data from¹ for Escherichia coli MG1655 also shows increase in cell division time noise as newborn cell size increases. Single-cell data was categorized in one of the four bins (1–2.8 μm, 2.8–4.5 μm, 4.5–6.3 μm, and 6.3–8 μm) depending upon newborn cell sizes. CV² of division time with 95% confidence interval (using bootstrapping) for each bin is shown (more details in SI, section S6).