The solution space of metabolic networks: producibility, robustness and fluctuations

TL;DR

This paper reviews flux analysis methods for biochemical networks and characterizes E.coli's metabolic capabilities, revealing a stable production profile amid significant fluctuations in key metabolites like ATP.

Contribution

It provides a detailed characterization of E.coli's metabolic producibility and highlights the variability in metabolite levels despite a stable production profile.

Findings

Stable production profile including biomass and waste components

Significant fluctuations in ATP and other key metabolites

Multiple growth scenarios compatible with the constraints

Abstract

Flux analysis is a class of constraint-based approaches to the study of biochemical reaction networks: they are based on determining the reaction flux configurations compatible with given stoichiometric and thermodynamic constraints. One of its main areas of application is the study of cellular metabolic networks. We briefly and selectively review the main approaches to this problem and then, building on recent work, we provide a characterization of the productive capabilities of the metabolic network of the bacterium E.coli in a specified growth medium in terms of the producible biochemical species. While a robust and physiologically meaningful production profile clearly emerges (including biomass components, biomass products, waste etc.), the underlying constraints still allow for significant fluctuations even in key metabolites like ATP and, as a consequence, apparently lay the ground for very different growth scenarios.