Structural fragility of the methylotrophic network. Prediction of reaction essentiality from Minimal Cut Set (MCS) analysis and comparison with experimental mutant phenotypes. The fragility coefficient (FC) calculated from MCS analysis is given for each reaction of M. extorquens central metabolism, and ranges from 0 (fully dispensable reaction) to 1 (essential reaction). Boxes next to reactions represent enzymes. Where available, the phenotype of the mutant lacking the gene encoding a particular enzyme is given by a color code (see legend). The occurrence of alternate reactions that are not displayed on the map is indicated by a star.