In a cell or microorganism, the processes that generate mass, energy, infor
mation transfer and cell-fate specification are seamlessly integrated throu
gh a complex network of cellular constituents and reactions(1). However, de
spite the key role of these networks in sustaining cellular functions, thei
r large-scale structure is essentially unknown. Here we present a systemati
c comparative mathematical analysis of the metabolic networks of 43 organis
ms representing all three domains of life. We show that, despite significan
t variation in their individual constituents and pathways, these metabolic
networks have the same topological scaling properties and show striking sim
ilarities to the inherent organization of complex non-biological systems(2)
. This may indicate that metabolic organization is not only identical for a
ll living organisms, but also complies with the design principles of robust
and error-tolerant scale-free networks(2-5), and may represent a common bl
ueprint for the large-scale organization of interactions among all cellular
constituents.