Defined synthetic microbial electrosynthesis (MES) consortia constructed by pairing the model bidirectional electroactive bacterium Shewanella oneidensis MR-1 with either the electroactive acetogen Clostridium aceticum or the nonelectroactive acetogen Acetobacterium woodii, mimicking functional guilds of natural MES communities. Co-cultivation boosts CO2-to-acetate production by up to 88%. The two pairings use distinct interspecies electron transfer (IET) modes, namely direct interspecies electron transfer (DIET) via cytochrome c and riboflavin at the biofilm-electrode interface in the S. oneidensis-C. aceticum consortium, versus H2/formate-mediated IET in the planktonic phase for the S. oneidensis-A. woodii consortium. This metabolic stratification lets S. oneidensis act as an "ecosystem engineer" orchestrating electron flow across biofilm and suspension niches.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Shewanella oneidensis MR-1 — ontology label: Shewanella oneidensis | NCBITaxon:70863 · TaxonMech · TraitMech |
ELECTROGEN
ELECTRON_DONOR
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| Clostridium aceticum (electroactive acetogen) — ontology label: Andreesenella acetica | NCBITaxon:84022 · TaxonMech · TraitMech |
ELECTROTROPH
ELECTRON_ACCEPTOR
SYNTROPHIC_PARTNER
|
N/A |
|
|||
| Acetobacterium woodii (nonelectroactive acetogen) — ontology label: Acetobacterium woodii | NCBITaxon:33952 · TaxonMech · TraitMech |
ELECTRON_ACCEPTOR
SYNTROPHIC_PARTNER
|
N/A |
|
|||
Ecological Interactions
The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.
Proposed Biofilm-Associated IET in the S. oneidensis-C. aceticum Pair
PARTIAL: In the C. aceticum-S. oneidensis pair, biofilm-associated electron transfer is supported by compartment-removal responses, electrochemical and spectroscopic readouts, and riboflavin add-back. The authors call this DIET, but these assays do not uniquely establish contact-only transfer or selective cytochrome necessity; riboflavin is also a diffusible mediator. The canonical target label Andreesenella acetica preserves the source organism called C. aceticum. Product enhancement does not demonstrate obligatory syntrophy.
Source Taxon: Shewanella oneidensis MR-1
Target Taxon: Clostridium aceticum (electroactive acetogen)
Metabolites: riboflavin (CHEBI:17015 · MediaIngredientMech · CMMMech)
PARTIAL: Biofilm-associated electron supply and riboflavin-responsive transfer can support the C. aceticum pair's acetate increase. Compartment removal and add-back support this contribution, but do not isolate the necessity of contact-only DIET or a specific cytochrome. This arrow concerns the CS pair, not a simultaneous three-member culture.
Evidence
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PMID:41236292 - PARTIAL (IN_VITRO)"DIET via cytochrome c and riboflavin dominates at the biofilm-electrode interface in S. oneidensis-C. aceticum consortia"
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PMID:41236292 - SUPPORT (IN_VITRO)"metabolite profiling (H2, formate, riboflavin), biomass distribution and fhs gene copy numbers, and functional prediction"
Proposed Planktonic H2/Formate IET in the S. oneidensis-A. woodii Pair
PARTIAL: The A. woodii-S. oneidensis pair favors suspension-associated acetate synthesis, consistent with a diffusible hydrogen/formate electron-transfer model. These culture-level profiles and compartment interventions do not trace donor-resolved transfer or establish an exclusive route; hydrogen was detected in both alternative pairs. Daily apparent biofilm/suspension contributions are instantaneous responses to cell removal, not cumulative mass-balanced flux fractions, and may exceed 100% through compensatory responses.
Source Taxon: Shewanella oneidensis MR-1
Target Taxon: Acetobacterium woodii (nonelectroactive acetogen)
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech)
PARTIAL: Diffusible reducing equivalents are a supported explanation for suspension-associated acetate synthesis in the AS pair, including acetate production where A. woodii alone failed at the tested lower cell voltage. This does not establish exclusive hydrogen/formate mediation or identify the molecular donor flux.
Evidence
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PMID:41236292 - PARTIAL (IN_VITRO)"whereas S. oneidensis-A. woodii consortia prefer H2/formate-mediated IET in the planktonic phase"
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PMID:41236292 - SUPPORT (IN_VITRO)"failed to produce acetate"
Enhanced CO2-to-Acetate Conversion
Two alternative two-member consortia, not one three-member community, increased acetate accumulation relative to their corresponding acetogen monocultures. At 0.88-V applied cell voltage, AS reached 1.16 g/L versus 0.62 g/L for A. woodii alone, and CS reached 1.05 g/L versus 0.56 g/L for C. aceticum alone. The participating taxa are the combined comparison roster; the acetogens were alternatives. Open-circuit cultures used H2/CO2 whereas driven cultures used N2/CO2, so that contrast is not voltage-only. Aggregate production does not prove reciprocal fitness or obligate syntrophy.
Participating Taxa: Shewanella oneidensis MR-1, Clostridium aceticum (electroactive acetogen), Acetobacterium woodii (nonelectroactive acetogen)
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- carbon fixation (GO:0015977 · PathwayMech)
Evidence
-
PMID:41236292 - SUPPORT (IN_VITRO)"Co-cultivation markedly boosts acetate production by up to 88%"
-
PMID:41236292 - PARTIAL (IN_VITRO)"orchestrating electron flow to optimize CO2-to-acetate conversion"
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PMID:41236292 - SUPPORT (IN_VITRO)"representing a 1.87‐fold of A. woodii alone"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which electron-transfer routes are necessary within each alternative pair?
Keep the two measured alternative pairs separate. Spectroscopy, electrochemistry, metabolite profiles, riboflavin add-back and daily planktonic-cell removal support compartment-associated models but do not isolate contact-only DIET or donor-resolved hydrogen/formate flux. Riboflavin is a diffusible mediator; hydrogen appears in both systems. Instantaneous apparent compartment contributions can exceed 100% and are not cumulative flux partitions. Main Methods describe DNA/16S, fhs copies and normalized gene abundance; do not call these transcript measurements without reviewing the unread supplement. The proposed acetate-formate recycling and future three-member consortium are hypotheses, not new measured causal nodes. Preserve canonical taxonomy and leave non-graph role, voltage and control wording to #1455.
Attaches to: ecological_interactions#Proposed Biofilm-Associated IET in the S. oneidensis-C. aceticum Pair, ecological_interactions#Proposed Planktonic H2/Formate IET in the S. oneidensis-A. woodii Pair, ecological_interactions#Enhanced CO2-to-Acetate Conversion
Growth Media
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