Figure 4.

Intraspecies FCA. (a) E. coli; (b) Salmonella enterica; (c) S. pneumoniae; and (d) H. pylori. Both genes (top) and codons (bottom) are plotted on the two first axes of the FCA. Codons are labeled according to the nature of the base at the third position. The percentages of variability explained by the axes are shown between brackets.