EAA production by Buchnera aphidicola APS. (A) export under different substrate inputs. Equal export under the two models is shown by the dashed line. Standard single letter abbreviations are used for EAAs. (B) Metabolic coupling between the purine and histidine biosynthetic pathways. The reactions present in E. coli are represented with white arrows representing reactions absent from B. aphidicola and grey arrows indicating the recycling of ATP between the purine and histidine biosynthetic pathways. Full metabolite names can be found in Supplementary File 1.