Robertson, W. E.; Rehm, F. B. H.; Spinck, M.; Schumann, R. L.; Tian, R.; Liu, W.; Gu, Y.; Kleefeldt, A. A.; Day, C. F.; Liu, K. C.; Christova, Y.; Zurcher, J. F.; Boege, F. L.; Birnbaum, J.; van Bijsterveldt, L.; Chin, J. W.

The near-universal genetic code of living organisms uses 64 codons to encode the 20 canonical amino acids in protein synthesis. Here we design and generate a variant of Escherichia coli with a 4 Mb synthetic genome in which we replace every known occurrence of six sense codons and a stop codon with synonymous codons. We thereby recode 105 codons to create an organism with a 57-codon genetic code; this organism - which we name Syn57 - uses 55 codons to encode the 20 canonical amino acids.