Figure 2.

Rapid sibling individualization is also apparent during subsequent outgrowth. (A) Representative phase contrast images of a TLFM microscopy image sequence of growing E. coli MG1655 cells at indicated times before and after heat treatment (52 °C, 6 min). The scale bar corresponds to 5 µm. (B) Fraction of cells surviving the heat treatment (52 °C, 6 min) binned by their predicted relative cell cycle position (n = 848). None of the individual bins were found to differ significantly from the average of all cells (orange line, 55.8%, 95% CI = [52.47%, 59.1%]; Fisher’s exact test, α = 0.01; asterisks indicate significant differences). Indicated in white is the total number of cells that was observed for each bin. (C) Fraction of sister cells with coupled cell fate (i.e. both cells either survive or die) is binned by the average predicted relative cell cycle position of the siblings (n = 424 sibling pairs). Indicated in white is the total number of sibling pairs that was observed for each bin. Orange line indicates the amount of coupling that would be expected by chance (50.7%, given the overall level of survival), asterisks indicate significant differences (Fisher’s exact test, α = 0.01). Note that the overall empirical fraction of siblings with shared cell fate (54.5%) is not significantly different from what would be expected by chance (p-value = 0.11). (D) Resuscitation time distribution of cells surviving the heat treatment (52 °C, 6 min; n = 473). The time individual surviving cells needed to resume growth was determined and binned to create the resuscitation time distribution. (E) Correlation between resuscitation times of surviving sister cell pairs (n = 140 sibling pairs, Pearson’s r = 0.4975, p-value = 1.04 × 10⁻⁹). (F) Evolution of the correlation between surviving siblings’ resuscitation times as these cells progress through their cell cycle. Shown is a schematic of two sibling cells progressing through their corresponding cell cycles. Depending on the timing of the heat treatment (orange arrow), with respect to the relative cell cycle progression of these cells, the correlation of their corresponding resuscitation times (in the case both siblings were able to survive) diminishes as cells advance. Correlations are shown for different cell cycle progression intervals (0–0.05, 0.05–0.2, 0.2–0.4 and 0.4–1, respectively) based on the average predicted relative cell cycle position of surviving siblings (n = 25, 38, 48 and 28 sibling pairs, respectively). Both the strength (respective Pearson’s r-values: 0.6154, 0.5697, 0.4117 and 0.3597, respective bootstrapped 95% CI: [0.3692, 0.8222], [0.3813, 0.7232], [0.1495, 0.6377] and [−0.0364, 0.6947]) and the significance (respective p-values: 4.78 × 10⁻⁴, 1.9 × 10⁻⁴, 5.49 × 10⁻³ and 5.83 × 10⁻²) of these correlations decline gradually as surviving siblings progress through their cell cycle before the heat treatment (52 °C, 6 min).