Fig. 2
From: The evolutionary dynamics of tRNA-gene copy number and codon-use in E. coli.
The codons enriched in Shigella SGE’s correspond to high copy number tRNA genes. a. The numbers of each tRNA gene, relative to E. coli MG1655. One representative strain of the O157:H7 strains (Sakai, blue) and Shigella strains (S. flexneri 2A 2457T, red) are shown for clarity, see Additional file 2: Figure S1 for the results using other Shigella and O157:H7 strains. Significant (greater than two fold enrichment, Mann-Whitney’s U) tRNA genes are labeled. b. The relative use of codons in the set of SGE elements that have multiple copies in Shigella strains. Each point shows the average enrichment of that given codon among the five Shigella strains used in this study, error bars are 99 % confidence intervals. Significance was calculated using Mann-Whitney’s U (colored circles)