A coastal-sediment-derived, granular-activated-carbon-dependent enrichment consortium serially transferred for about a decade from Bothnian Bay sediments. In anaerobic, acetate-fed cultures amended with granular activated carbon (GAC), the consortium couples syntrophic acetate oxidation to methane formation by moving electrons from the dominant electrogenic syntroph Candidatus Geosyntrophus acetoxidans through the GAC matrix to a Methanosarcina-related electrotrophic methanogen. Long-read metagenomics recovered 24 MAGs from the GAC-propagated enrichment, including MAGs for the core acetate-oxidizing and methanogenic partners plus GAC-enriched Lentimicrobium, Sedimentibacter, and Desulforhopalus lineages.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Candidatus Geosyntrophus acetoxidans GAC.MBAT.93 — ontology label: Bacteria | NCBITaxon:2 · TaxonMech · TraitMech |
ELECTROGEN
ELECTRON_DONOR
SYNTROPHIC_PARTNER
|
DOMINANT |
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| Baltic Methanosarcina MAG GAC.MBAT.2 — ontology label: Methanosarcina | NCBITaxon:2207 · TaxonMech · TraitMech |
ELECTROTROPH
ELECTRON_ACCEPTOR
SYNTROPHIC_PARTNER
|
DOMINANT |
|
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| Lentimicrobium sp. GAC-specific MAG — ontology label: Lentimicrobium | NCBITaxon:1840214 · TaxonMech · TraitMech |
ELECTRON_DONOR
SYNTROPHIC_PARTNER
SECONDARY_FERMENTER
|
ABUNDANT |
|
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| Sedimentibacter MAG in GAC incubations — ontology label: Sedimentibacter | NCBITaxon:190972 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
|
ABUNDANT |
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| Desulforhopalus MAG in GAC incubations — ontology label: Desulforhopalus | NCBITaxon:40413 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
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ABUNDANT |
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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.
GAC-mediated syntrophic acetate oxidation to methane
SYNTROPHYThe GAC-dependent enrichment supports syntrophic acetate oxidation coupled to Methanosarcina methane production through a conductive scaffold. Serial GAC-free transfers were nearly inactive and key electrogenic/methanogenic populations became poorly detected, not demonstrably absent; residual Methanosarcina reached about 0.06%. Assignment of the core route to Candidatus Geosyntrophus acetoxidans GAC.MBAT.93 and Methanosarcina GAC.MBAT.2 combines enrichment evidence, genomes and prior physiology. Specific porin-cytochrome, MmcA and pilus steps remain proposed rather than molecularly isolated in these MAGs.
Source Taxon: Candidatus Geosyntrophus acetoxidans GAC.MBAT.93
Target Taxon: Baltic Methanosarcina MAG GAC.MBAT.2
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
-
PMID:41876513 - SUPPORT (IN_VITRO)"the Baltic Sea Geobacter continued to oxidize acetate and transfer electrons through the GAC matrix"
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PMID:41876513 - SUPPORT (IN_VITRO)"confirming that the electrically conductive scaffold provided by GAC remains indispensable for SAO after a decade of serial cultivation and enrichment"
Lentimicrobium alternative EET-linked acetate oxidation
SYNTROPHYA GAC-specific Lentimicrobium MAG encodes a large porin-multiheme-cytochrome cluster and a complete acetate uptake and utilization pathway, suggesting a secondary acetate-oxidizing route that could feed electrons to the Methanosarcina partner through extracellular electron transfer or allow persistence by fermentative recycling.
Source Taxon: Lentimicrobium sp. GAC-specific MAG
Target Taxon: Baltic Methanosarcina MAG GAC.MBAT.2
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
-
PMID:41876513 - PARTIAL (COMPUTATIONAL)"Lentimicrobium may sustain its activity via DIET with methanogens or by fermentatively recycling organic intermediates released within the consortium."
Auxiliary biomass turnover in the GAC enrichment
CROSS_FEEDINGSedimentibacter, Desulforhopalus, and possibly Lentimicrobium are inferred to occupy auxiliary recycling niches that consume biomass-derived organic matter released within the conductive-particle enrichment rather than driving the main GAC-to-methanogen electron flow.
Participating Taxa: Sedimentibacter MAG in GAC incubations, Desulforhopalus MAG in GAC incubations, Lentimicrobium sp. GAC-specific MAG
Evidence
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PMID:41876513 - PARTIAL (COMPUTATIONAL)"their primary ecological role may not be related to direct electron transfer, but rather to the recycling of organic matter resulting from biomass turnover within the community"
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PMID:41876513 - PARTIAL (COMPUTATIONAL)"Desulforhopalus is unlikely to be involved in SAO but may be involved in biomass turnover like Sedimentibacter."
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Bothnian Bay GAC consortium metagenome assemblies
NCBI BioProject containing raw metagenome reads and MAG assemblies for GAC-incubation and particle-free incubations, plus the Geobacter psychrophilus P39 genome sequenced for phylogenomic comparison. |
METAGENOMICS | NCBI_BIOPROJECT | PRJNA1140524 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which molecular routes and auxiliary partners mediate GAC-dependent syntrophic acetate oxidation?
Preserve experimentally supported GAC-dependent syntrophy, not just a genomic hypothesis. Particle-free inactivity is distinct from complete disappearance of every methanogen. Lentimicrobium and biomass-turnover roles remain PARTIAL computational alternatives. Prior isotope/inhibitor/NanoSIMS work was read as summarized by the current paper, not independently re-reviewed. Full main text/captions read, not images or supplements; transfer-count and vessel metadata follow-up is #1268.
Attaches to: ecological_interactions#GAC-mediated syntrophic acetate oxidation to methane, ecological_interactions#Lentimicrobium alternative EET-linked acetate oxidation, ecological_interactions#Auxiliary biomass turnover in the GAC enrichment
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Primary publication - GAC-dependent Bothnian Bay CIET-SAO consortium
Open-access Nature Communications study resolving the MAGs and inferred extracellular-electron-transfer machinery of the GAC-obligate acetate-to- methane consortium. |
OTHER | PMID:41876513 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Granular activated carbon dependence | required for long-term SAO activity | N/A |
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Growth Media
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