The Canonical Network of Autotrophic Intermediary Metabolism: Minimal Metabolome of a Reductive Chemoautotroph

Chemoautorophs that fix carbon by the reductive tricarboxylic acid cycle represent one of the dominant bacterial life forms that make a major contribution to biomass production. From the viewpoint of biogenesis, construction of a canonical chart of intermediary metabolism for this class of organisms may help us to understand early cellular evolution and point us to the last universal common ancestor. Data-mining the KEGG Pathways database enabled us to integrate required biosynthetic pathways and derive a chart that represents the complete anabolic network of a reductive chemoautotroph. Compounds of this metabolic network together constitute a representative minimal metabolome that comprises 287 metabolites. These compounds have been classified into different groups including those compounds that form nodes in the network. It can be seen that a relatively sparse set of organic chemical reactions dominate the anabolic synthesis in the assembly of the minimal autotrophic metabolome. Empirical generalizations that result from analyzing this metabolic network may aid in elucidating selection rules that govern its emergence and further evolution and may also help in delineating attributes that impart the observed robustness to these metabolites.