Solving the Mystery of Metabolism in Clostridium acetobutylicum – an Important Biofuel Producer

Obligatory anaerobes encompass some of the most promising bioenergy organisms.

The Science

The bacterium Clostridium acetobutylicum produces butanol, ethanol, and hydrogen as end products of biomass fermentation and already has industrial uses. C. acetobutylicum also serves as a model for an important class of soil-based organisms mediating carbon degradation in terrestrial ecosystems. However, scientists have not been able to map this organism’s metabolic processes since the genes encoding several key enzymes necessary for basic cell physiology seem to be missing. DOE scientists at Princeton University have used an innovative approach to resolve this mystery. By following the incorporation of radiolabeled carbon into various intermediate compounds, they identified a unique series of reactions used in carbon conversion and developed the first ever quantitative model of metabolic flux for C. acetobutylicum. These results provide critical information on the pathway used by these organisms to perform important processes in the global carbon cycle and greatly enhance the prospects of being able to engineer Clostridia’s metabolism for biofuels synthesis.

The Impact

The investigation also yielded insights into the pathways utilized for glucose catabolism and amino acid biosynthesis and revealed that the organism’s one-carbon metabolism is distinct from that of model microbes, involving reversible pyruvate decarboxylation and the use of pyruvate as the one-carbon donor for biosynthetic reactions. This study represents the first in vivo characterization of the TCA cycle and central metabolism of C. acetobutylicum.

BER Program Manager

Dawn Adin

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]


Amador-Noguez, D., X.-J. Feng, J. Fan, N. Roquet, H. Rabitz and J. D. Rabinowitz. 2010 “Systems-Level Metabolic Flux Profiling Elucidates a Complete, Bifurcated TCA Cycle in Clostridium acetobutylicum”, Journal of Bacteriology. DOI:10.1128/JB.00490-10.