Fig. 1.

Illustration of culture methods for long-term evolution. Fifty WT and 50 mutL− (mismatch-repair deficient) E. coli K-12 MG1655 populations were established from a single isolated colony and grown in glass culture tubes containing 10 mL of LB broth. Cultures were propagated by alternating 37 °C incubation for 24 h with 25 °C incubation for 48 h. Further, five different evolution treatments were established by varying the volume of the transfer bottleneck. Populations were thoroughly vortexed before each transfer, and whole communities were subjected to whole-genome sequencing every 6 mo.