Figure 8

Comparison of the distribution of amino acid biosynthetic costs among the three domains. The amino acid biosynthetic cost was as reported by Seligmann [47]. Briefly, the molecular weight was used as a proxy for biosynthetic cost, which has the advantage in comparisons across species of being independent of the pathways for amino acid synthesis [46, 47]. The cost in each species was taken as the accumulation of the costs of the 20 amino acid costs (amino acid percentage multiplied its molecular weight).