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Sci Rep. 2017 Mar 21;7(1):268. doi: 10.1038/s41598-017-00170-3.

Robust Analysis of Fluxes in Genome-Scale Metabolic Pathways.

Scientific reports

Michael MacGillivray, Amy Ko, Emily Gruber, Miranda Sawyer, Eivind Almaas, Allen Holder

Affiliations

  1. Department of Mathematics, Rose-Hulman Institute of Technology, Terre Haute, IN, USA.
  2. Department of Biotechnology, NTNU - Norwegian University of Science and Technology, Trondheim, Norway. [email protected].
  3. K.G. Jebsen Center for Genetic Epidemiology, Department of Public Health and General Practice, NTNU - Norwegian University of Science and Technology, Trondheim, Norway. [email protected].
  4. Department of Mathematics, Rose-Hulman Institute of Technology, Terre Haute, IN, USA. [email protected].

PMID: 28325918 PMCID: PMC5427939 DOI: 10.1038/s41598-017-00170-3

Abstract

Constraint-based optimization, such as flux balance analysis (FBA), has become a standard systems-biology computational method to study cellular metabolisms that are assumed to be in a steady state of optimal growth. The methods are based on optimization while assuming (i) equilibrium of a linear system of ordinary differential equations, and (ii) deterministic data. However, the steady-state assumption is biologically imperfect, and several key stoichiometric coefficients are experimentally inferred from situations of inherent variation. We propose an approach that explicitly acknowledges heterogeneity and conducts a robust analysis of metabolic pathways (RAMP). The basic assumption of steady state is relaxed, and we model the innate heterogeneity of cells probabilistically. Our mathematical study of the stochastic problem shows that FBA is a limiting case of our RAMP method. Moreover, RAMP has the properties that: A) metabolic states are (Lipschitz) continuous with regards to the probabilistic modeling parameters, B) convergent metabolic states are solutions to the deterministic FBA paradigm as the stochastic elements dissipate, and C) RAMP can identify biologically tolerable diversity of a metabolic network in an optimized culture. We benchmark RAMP against traditional FBA on genome-scale metabolic reconstructed models of E. coli, calculating essential genes and comparing with experimental flux data.

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