Figure 3. Quantitative analysis of cellular straightening dynamics.

a, In our experiments, filamentous E. coli cells were grown in confined, toroidal microchambers of diameter d = 8 μm. An elastic snapback was observed upon removal, after which the cells recovered their straight, rod-like morphologies over time. Images shown correspond to before (0 min and 90 min) and after (2 min, 10 min, 20 min, and 30 min) microchamber release. b, Histograms for the instantaneous growth rate λ = dL/(Ldt) and instantaneous straightening rate μ = −dC/(Cdt) for 60 E. coli cells. c, A plot of the log normalized curvature, defined as ln(C(t)/C(2 min)), as a function of time since release (in units of t_d/ ln(2)) for all 60 cells in Phase 2. A 50-point moving average filter along the temporal direction was applied to smooth out the data. The population-averaged straightening-to-growth ratio is 〈μ〉/〈λ〉 = 1.8, which cannot be explained by an infinite processivity of PG synthesis. The slower rate of decrease of the log normalized curvature for large times may be an artifact of substrate pinning for large cells. d, (Left) Extrapolating the population-averaged curvature to the time of microchamber release at t = 0 yields a mean elastic snapback ratio of κ = 0.78 ± 0.09. Shaded areas denote values within one standard deviation of the population mean. The gray dashed lines denote exponential fits to values which are one standard deviation away from the population average. (Right) The distributions of aggregated normalized curvatures C(t)/C(0) at times t = 2–16 min and t = 16–30 min.