Fig. 1: Efficient unnatural amino acids incorporation and generalizable synthetic auxotroph construction with the evolved chimeric Phe system.

Schematic illustration of the engineering of orthogonal translation systems with wild-type like efficiency in the presence of UAA and low background activity in the absence of UAA. The orthogonal translation system is used to construct UAA-dependent synthetic auxotroph by inserting amber codons into the essential gene. EP refers to essential protein.