Adaptive evolution of genomically recoded Escherichia coli
Significance The construction of an organism with an altered genetic code negatively impacted its fitness. We evolved this organism for ∼1,100 generations in the laboratory to recover fitness and learn what changes would accumulate during evolutionary trajectories toward faster growth rates. We observed several selective mutations that helped alleviate insufficient translation termination or that corrected for unintended mutations that accumulated when we originally altered the genetic code. Further observed mutations were generally adaptive in a nonrecoded background. This work bolsters our understanding of the pliability of the genetic code and will help guide future efforts seeking to recode genomes. Finally, it results in a useful strain for nonstandard amino acid incorporation in numerous contexts relevant for research and industry.