Fig. 2.

Example for disruption of growth coupling and for accessible metabolites. In the lower branch there are three different cuts (green, blue, blue) that establish coupling of biomass and product synthesis. All of them cut the same pathway and lead to the same solution space but they imply a different number of accessible metabolites. The green cut at the beginning of the pathway is preferred and has the lowest number of accessible metabolites. Choosing the green cut (or, less favored, one of the two red cuts), coupling is ensured and the product is synthesized if the cell grows, however, excretion of the metabolites E and G (but not F) would disrupt growth coupling (Color version of this figure is available at Bioinformatics online.)