Figure 5

Correlation between codon usage in a transcript and fitness. The bar indicates the Pearson correlation value between codon frequency and OD. On the x-axis are listed all the codons in the format 'codon (amino acid)'. A correlation was determined to be significant if its P-value is below 0.05/61 (that is, alpha = 0.05 was corrected for the number of codons tested). Red bars represent codons for which there is a significantly positive correlation between their appearance and the OD. Blue bars represent codons that have a significant negative correlation. For codons with no significant correlation, grey squared bars are used. When no bar appears for a codon (for example AUG, UAA and so on) it means that the usage of that specific codon was constant for all genes, thus resulting in no correlation value. For usage of each amino acid in the GFP variant, see Table S3 in Additional file 1.