Amberless E. coli evolution to compensate for growth defect. synthetic Escherichia coli C321.deltaA

We evolved the recoded "amberless" E. coli that is used for incorporating nonstandard amino acids at the TAG codon in the laboratory. We observed parallel mutations in folA (dihydrofolate reductase) that significantly improved its growth rate in minimal and rich media, suggesting that a defect in tetrahydrofolate metabolism limits growth of this engineered strain.