Metabolic Flux Analysis Based on Stable Isotopes

Metabolic fluxes are at the heart of systems biology. Their quantification allows investigating the ultimate physiological response to environmental changes and/ or disease related disruptions.

While most metabolic flux analysis is based on labelled organic substrates, our approach is distinguished by the use of labelled bicarbonate. Bicarbonate as tracer has the advantage that it conserves the original organic carbon regime. Its heterotrophic fixation at specific metabolic nodes allows tracing the direction of metabolic fluxes from within the network. We aim to take advantage of this opportunity by investigating the organic substrate dependent bicarbonate fixation in heterotrophs to further use labelled bicarbonate as an in-situ biomarker for metabolic alterations in microbial communities and humans.


  • M. Spona-Friedl, A. Braun, C. Huber, W. Eisenreich, Ch. Griebler, A. Kappler, M. Elsner, Substrate-dependent CO2-fixation in heterotrophic bacteria revealed by stable isotope labelling, FEMS Microbiology Ecology 96 (2020), Volume 96, Issue 6, June 2020, fiaa080 DOI: 10.1093/femsec/fiaa080A.
  • Braun, M. Spona-Friedl, M. Avramov, M. Elsner, F. Baltar, Th. Reinthaler, G.J. Herndl, Ch. Griebler, Reviews and syntheses: Heterotrophic fixation of inorganic carbon –significant but invisible flux in environmental carbon cycling, Biogeosciences (2021), 3689–3700, https://doi.org/10.5194/bg-18-3689-2021