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Propionate oxidation by Geobacter sulfurreducens is electron acceptor dependent
David Hernández-Villamor1,2, Jean-Romain Bautista Angeli1,2,3, Aya Jeaidi1,2
1Center for Microbial Ecology and Technology (CMET), Ghent University, Ghent, Belgium.
Applied and Environmental Microbiology
|May 21, 2026
Summary
Geobacter sulfurreducens can oxidize propionate, a challenging compound in industrial processes. This bacterium utilizes propionate as an electron donor, expanding its known metabolic capabilities for improved anaerobic digestion.
Area of Science:
- Microbiology and Microbial Metabolism
- Bioelectrochemical Systems
- Environmental Biotechnology
Background:
- Propionate accumulation is a significant challenge in fermentative industrial processes due to its energetic limitations for degradation.
- Few microbial species can effectively degrade propionate, which can inhibit crucial processes like methanogenesis.
- Geobacter sulfurreducens is a model electroactive bacterium known for its role in syntrophic metabolism and bioelectrochemical systems.
Purpose of the Study:
- To investigate the ability of Geobacter sulfurreducens to oxidize propionate as an electron donor and carbon source.
- To determine the influence of different electron acceptors on propionate metabolism by G. sulfurreducens.
- To elucidate the metabolic pathways and transcriptional responses associated with propionate degradation in G. sulfurreducens.
Main Methods:
- Cultivation of axenic Geobacter sulfurreducens cultures with propionate as the sole carbon and electron source, using fumarate as the electron acceptor.
- Comparative growth studies with propionate alone, propionate plus acetate, and varying electron acceptors (fumarate, soluble Fe(III) citrate, insoluble iron oxides, glassy carbon electrodes).
- Transcriptomic analysis of G. sulfurreducens grown on propionate versus acetate to identify gene expression shifts.
Main Results:
- Geobacter sulfurreducens demonstrated the ability to oxidize propionate as both an electron donor and carbon source when fumarate was the electron acceptor.
- Propionate metabolism was observed only in the presence of acetate with soluble Fe(III) citrate, but not with insoluble iron oxides or poised electrodes.
- Transcriptomic data strongly indicated the methylmalonyl-CoA pathway as the primary route for propionate degradation, with associated changes in amino acid and sulfur metabolism.
Conclusions:
- Geobacter sulfurreducens possesses the capability to oxidize propionate via extracellular electron transfer, expanding its known metabolic versatility.
- The efficiency of propionate oxidation is dependent on the nature of the terminal electron acceptor.
- These findings provide insights into propionate degradation pathways and suggest potential applications for G. sulfurreducens in mitigating propionate accumulation in anaerobic systems.
Keywords:
G. sulfurreducensRNA-seqacetateelectron acceptorelectron donorfumaratepropionatetranscriptomic analysisMore Related Videos
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