Figure 2

Evolution experiment with UV exposure. (a) Schematics of the evolution experiment with UV radiation. The overnight cultures were transferred to fresh media in multiple-well microplates after a 100-fold dilution (5 wells for each independent lineage). Subsequently, the cells were exposed to UV irradiation through UV cut films so that each well was exposed to different UV doses. The cell cultures were incubated overnight at 37 °C. The wells which were exposed to the largest UV dose (indicated by an asterisk) were selected among the well-growing cultures (OD₅₉₅ > 0.1). This cycle was repeated for 28 days. We established six independent replications for each strain. (b) Schematic of the rounds of the evolution experiment without UV irradiation. The overnight cultures of the selected wells were transferred to fresh media with different dilution rates (10²-, 10³-, 10⁴-, 10⁵-, and 10⁶-fold). The wells which had the largest dilution rates (indicated by an asterisk) were selected among the well-growing cultures (OD₅₉₅ > 0.1). This cycle was repeated for 28 days. Six independent replications were established for each strain. (c) The time series of the UV doses. The mean values among the six lineages were plotted for each strain (Co, ΔS, and ΔHSB from left to right). The error bars represent standard deviations.