Figure 4.

Expected and observed amino acid compositions. We took four representative amino acids as examples: Asn (asparagine; A to C), Cys (cysteine; D to F), Ala (alanine; G to I), and Leu (leucine; J to L). The expected and observed amino acid compositions for the four amino acids were quantitated in Archaea (A, D, G and J), Bacteria (B, E, H and K), and Eukarya (C, F, I and L). Each point in all plots represents a sum of the composition from the species coding sequences and similar plots for all other amino acids were summarized in Additional file 4.