Comparison of mortality rates between the evolved E. coli and their ancestor under the prolonged freeze-only regime. The height of each bar shows the mean mortality rate per day for the evolved lines or their ancestor, measured over ten days at -80°C. For the evolved bacteria, the mean is calculated over all 12 lines, with three assays for each line. For the ancestor, the mean is calculated over two marked variants (Ara+ and Ara-), with three assays for each one. See the Materials and Methods section for the mortality rate calculation, which includes an adjustment for the mortality caused by thawing in the final day. Error bars are 95% confidence intervals based on the number of lines (evolved) or total assays (ancestor).