Evolution Experiments

Continuous cultures were established using media and conditions previously described (Gresham et al. 2008; Sanchez et al. 2017). Detailed protocols and media recipes are available at http://dunham.gs.washington.edu/protocols.shtml (last accessed March 6, 2017). Samples were taken daily and measured for optical density at 600 nm and cell count; microscopy was performed to check for contamination; and archival glycerol stocks were made daily. An experiment was terminated when contamination, growth in tubing, or clumping appeared (number of generations at the end point for each population are presented in tables 1 and ​and2).2). Samples from each end point population were colony purified to yield two clones for further study.