Fig 2. Example of two maximally different metabolisms.

Each arrow in each panel corresponds to one of the 51 internal reactions we consider. Black arrows and gray arrows correspond to reactions that are present or absent, respectively, in the metabolism shown. Metabolites are indicated by their acronyms (see S9 Table). Boxed metabolites correspond to 13 essential biomass precursors. Note that 4 metabolites (accoa, g3p, f6p and e4p) are shown more than once for visual clarity. a) A metabolism with 33 reactions that is viable on fructose and that differs from another metabolism of size 33 viable on fructose shown in b) by 16 reactions. The two metabolisms share 17 reactions.