Fig. 2

Heat map of the relative codon frequencies for E. coli grouped by amino acid. a Values from Sharp and Li (1986). The authors binned their datasets (see Table 1) into four groups as shown in the figure. An “X” represents no available data for the codon. b Codon distributions for various codon usage databases or datasets described in Table 1. Data for Dong et al. are from the growth rate at 2.5 h⁻¹