General Rules for Optimal Codon Choice
The most GC-rich codons in each codon family received a score of 1, the most AT rich codons in each codon family received a score of −1. For Arginine and Leucine codons of intermediate GC content received a score of 0. For each genome the GC scores of the optimal codons were summed and divided by the number of codon-families for which an optimal codon was identified. Thus an organism that has only GC-rich optimal codons received a score of 1, while an organism that uses only AT-rich optimal codons received a −1. These scores are plotted against the intergenic GC content. (A) All bacteria are included, and (B) one bacteria selected at random from each genus.