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. Author manuscript; available in PMC: 2022 Dec 15.
Published in final edited form as: Cell Syst. 2021 Sep 17;12(12):1187–1200.e4. doi: 10.1016/j.cels.2021.08.011

Figure 1. Replaying the first selective sweep of a long-term evolution experiment.

Figure 1.

Nine E. coli populations were initiated from equal mixtures of two variants of the ancestral strain that differ in a neutral genetic marker for arabinose utilization (Ara). We observed the evolutionary dynamics of these populations over 500 generations of regrowth from 75 daily 1:100 serial transfers by periodically plating dilutions of each population on indicator agar. Each ancestral strain subpopulation was derived from a single colony isolate that experienced 30 generations of growth before it was combined with the opposite type to initiate the serial transfers. The ratio of Ara+ cells (pink colonies) to Ara− cells (red colonies) diverges from 1:1 when descendants of one ancestor type accumulate enough of a fitness advantage due to de novo beneficial mutations that they take over. We focused further analysis on six of the nine populations (thick lines).