Hierarchical organization of modularity in metabolic networks

TL;DR

This paper demonstrates that metabolic networks across various organisms are hierarchically organized into modules, with a power-law distribution, and this structure correlates with known functions in E. coli, suggesting a universal cellular organization principle.

Contribution

It provides quantitative evidence for hierarchical modularity in metabolic networks across multiple species, linking network structure to cellular function.

Findings

Metabolic networks are organized into small, highly connected modules.

Modules combine hierarchically into larger units following a power-law distribution.

Hierarchical modularity in E. coli overlaps with known metabolic functions.

Abstract

Spatially or chemically isolated functional modules composed of several cellular components and carrying discrete functions are considered fundamental building blocks of cellular organization, but their presence in highly integrated biochemical networks lacks quantitative support. Here we show that the metabolic networks of 43 distinct organisms are organized into many small, highly connected topologic modules that combine in a hierarchical manner into larger, less cohesive units, their number and degree of clustering following a power law. Within Escherichia coli the uncovered hierarchical modularity closely overlaps with known metabolic functions. The identified network architecture may be generic to system-level cellular organization.