Evolution of E. coli on [U-13C]Glucose Reveals a Negligible Isotopic Influence on Metabolism and Physiology

PLoS One. 2016 Mar 10;11(3):e0151130. doi: 10.1371/journal.pone.0151130. eCollection 2016.

Abstract

13C-Metabolic flux analysis (13C-MFA) traditionally assumes that kinetic isotope effects from isotopically labeled compounds do not appreciably alter cellular growth or metabolism, despite indications that some biochemical reactions can be non-negligibly impacted. Here, populations of Escherichia coli were adaptively evolved for ~1000 generations on uniformly labeled 13C-glucose, a commonly used isotope for 13C-MFA. Phenotypic characterization of these evolved strains revealed ~40% increases in growth rate, with no significant difference in fitness when grown on either labeled (13C) or unlabeled (12C) glucose. The evolved strains displayed decreased biomass yields, increased glucose and oxygen uptake, and increased acetate production, mimicking what is observed after adaptive evolution on unlabeled glucose. Furthermore, full genome re-sequencing revealed that the key genetic changes underlying these phenotypic alterations were essentially the same as those acquired during adaptive evolution on unlabeled glucose. Additionally, glucose competition experiments demonstrated that the wild-type exhibits no isotopic preference for unlabeled glucose, and the evolved strains have no preference for labeled glucose. Overall, the results of this study indicate that there are no significant differences between 12C and 13C-glucose as a carbon source for E. coli growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Biological / genetics
  • Carbon Radioisotopes / toxicity*
  • DNA, Bacterial / chemistry
  • Escherichia coli / drug effects*
  • Escherichia coli / metabolism
  • Escherichia coli / physiology
  • Evolution, Molecular*
  • Genome, Bacterial
  • Glucose / metabolism*
  • Metabolic Flux Analysis
  • Sequence Analysis, DNA

Substances

  • Carbon Radioisotopes
  • DNA, Bacterial
  • Glucose

Grant support

This work was funded by the Novo Nordisk Foundation Center for Biosustainability (grant 2011-3780). TES is supported through the National Science Foundation Graduate Research Fellowship (grant DGE1144086). MRA and CPL are supported by NSF CAREER Award (CBET-1054120). CPL is also supported by the University of Delaware Graduate Fellows Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.