Metabolic Flux Analysis using 13C Isotopes: III. Significance for Systems Biology and Metabolic Engineering

At present, 13C-MFA is a primary method for quantitatively characterizing intracellular carbon fluxes in cells in vivo under steady-state conditions. The method has been successfully used to investigate both the fundamental characteristics of prokaryotic and eukaryotic cell metabolism and to improve producer strains for more than twenty years. This publication is the last in a set of reviews that describe various aspects of the method. Here, the authors highlight recent achievements that involved using 13C-MFA to elucidate bacterial metabolism. Analyses of well-characterized bacterial model strains revealed that central metabolism robustness is provided by a set of alternative metabolic pathways; these analyses also helped develop a better understanding of the physiological significance of these pathways and identified previously unknown functions of well-studied metabolic pathways. Several examples of 13C-MFA-based fundamental investigations of poorly characterized bacteria are also analyzed. In applied investigations, flux analysis of strains that produce amino acids, vitamins and antibiotics indicated targets for modifications, suggested unconventional metabolic engineering approaches, and, most importantly, confirmed their utility. In the last section of this article, 13C-MFA prospects, including the monitoring of the dynamics of metabolic flux distribution during culture growth, are discussed.