Figure 4

Cartographic representation for the metabolic networks of a. E. coli and b. Buchnera aphidicola. Each circle corresponds to a structural module. Colors represent KEGG pathway classification, where the fraction of each class is proportional to the significance level of that category in the module nodes obtained from a hypergeometric test. Circle size is proportional to module's size and the thickness of edges proportional to the number of interactions between two modules. In E. coli most of the modules are functionally pure, and each metabolic class can be assigned to a specific structural module. In Buchnera network, modules are less pure and show more mixture of different functions. In three models, however, pureness of amino acid metabolism can be detected (e.g. the basis for the symbiosis with aphids)