A thermophilic, high-ammonia syntrophic butyrate-oxidizing enrichment culture maintained in yeast-extract-free 0B medium after derivation from a propionate-fed biogas reactor community. The enrichment was inoculated from a laboratory bioreactor that originated from large-scale food- and slaughterhouse-waste digestate, then followed as a single long-running, butyrate-fed anaerobic culture at 51 C for 972 days. Amplicon and metagenomic analyses recovered MAG1, a putative novel ammonia-tolerant syntrophic butyrate oxidizer proposed as Candidatus Syntrophothermus ammoniitolerans, together with a putative syntrophic acetate-oxidizing MAG related to Candidatus Thermosyntrophaceticus schinkii and hydrogenotrophic Methanoculleus and Methanothermobacter MAGs that likely close the network by consuming formate or H2 and producing methane.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Candidatus Syntrophothermus ammoniitolerans MAG1 — ontology label: Syntrophothermus | NCBITaxon:129001 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
ELECTRON_DONOR
|
ABUNDANT |
|
|||
| Candidatus Thermosyntrophaceticus-like SAOB MAG2 — ontology label: Bacteria | NCBITaxon:2 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
SYNTROPHIC_PARTNER
ELECTRON_DONOR
|
COMMON |
|
|||
| Candidatus Methanoculleus thermohydrogenotrophicum MAG3 — ontology label: Candidatus Methanoculleus thermohydrogenotrophicum | NCBITaxon:1671625 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
ELECTRON_ACCEPTOR
CROSS_FEEDER
|
DOMINANT |
|
|||
| Methanothermobacter wolfeii and tenebrarum MAGs — ontology label: Methanothermobacter | NCBITaxon:145260 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
ELECTRON_ACCEPTOR
CROSS_FEEDER
|
DOMINANT |
|
|||
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.
Syntrophic Butyrate Oxidation by MAG1
SYNTROPHYPARTIAL - cultivation and metagenomics support MAG1 as a putative syntrophic butyrate oxidizer. The single long-term 0B culture converted butyrate to methane, while MAG1 beta-oxidation and energy-conservation genes support the proposed organism-level role. Acetate provision to the putative MAG2 acetate oxidizer and carrier consumption by methanogens form the authors' model, not measured MAG-specific flux or a selectively tested partner requirement. The source-to-target pair represents the proposed acetate branch, not transfer of every listed metabolite to MAG2.
Source Taxon: Candidatus Syntrophothermus ammoniitolerans MAG1
Target Taxon: Candidatus Thermosyntrophaceticus-like SAOB MAG2
Metabolites: butyrate (CHEBI:17968 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)
Biological Processes:
- fatty acid beta-oxidation (GO:0006635 · PathwayMech)
PARTIAL - proposed MAG1 butyrate oxidation supplies acetate that MAG2 could oxidize while Methanoculleus consumes released hydrogen or formate, supporting the modeled coupled conversion. Bulk conversion and genomic potential do not establish this exact partner-resolved flux or the hydrogen/formate split.
PARTIAL - proposed MAG1 butyrate oxidation supplies acetate that MAG2 could oxidize while Methanothermobacter consumes released hydrogen or formate, supporting the modeled coupled conversion. Bulk conversion and genomic potential do not establish this exact partner-resolved flux or the hydrogen/formate split.
Evidence
-
PMID:42527912 - PARTIAL (COMPUTATIONAL)"Acetate produced during butyrate oxidation was further oxidized by syntrophic acetate-oxidizing bacteria and ultimately converted to methane by hydrogenotrophic methanogens"
-
PMID:42527912 - SUPPORT (IN_VITRO)"Thereafter, the 0B culture subsequently converted butyrate to methane without substantial lag phases during the subsequent seven butyrate depletion cycles"
Syntrophic Acetate Oxidation by MAG2 to Methanoculleus
SYNTROPHYPARTIAL - the authors infer acetate oxidation by MAG2 coupled to hydrogen- or formate-consuming Methanoculleus MAG3. MAG2 is a moderate-quality genome without a completely annotated Wood-Ljungdahl pathway; the close-relative comparison supports a hypothesis, not observation of its missing genes or active acetate flux. Methanogen genomic potential supports the proposed partner role without resolving carrier partition or proving that each partner is necessary.
Source Taxon: Candidatus Thermosyntrophaceticus-like SAOB MAG2
Target Taxon: Candidatus Methanoculleus thermohydrogenotrophicum MAG3
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- acetate catabolic process (GO:0045733 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
-
PMID:42527912 - PARTIAL (COMPUTATIONAL)"suggesting that MAG2 also possesses the genomic potential for SAO"
-
PMID:42527912 - PARTIAL (COMPUTATIONAL)"members of the genera Methanoculleus and Methanothermobacter likely served as hydrogenotrophic methanogenic partners"
Syntrophic Acetate Oxidation by MAG2 to Methanothermobacter
SYNTROPHYPARTIAL - the authors infer acetate oxidation by MAG2 coupled to hydrogen- or formate-consuming Methanothermobacter MAG4/MAG5. MAG2 is a moderate-quality genome without a completely annotated Wood-Ljungdahl pathway; the close-relative comparison supports a hypothesis, not observation of its missing genes or active acetate flux. Methanogen genomic potential supports the proposed partner role without resolving carrier partition or proving that each partner is necessary. Late relative enrichment of Methanothermobacter does not establish an improved butyrate-conversion rate. Proposed acetate assimilation by MAG5 is distinct from acetoclastic methane production.
Source Taxon: Candidatus Thermosyntrophaceticus-like SAOB MAG2
Target Taxon: Methanothermobacter wolfeii and tenebrarum MAGs
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- acetate catabolic process (GO:0045733 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
-
PMID:42527912 - PARTIAL (COMPUTATIONAL)"suggesting that MAG2 also possesses the genomic potential for SAO"
-
PMID:42527912 - PARTIAL (COMPUTATIONAL)"members of the genera Methanoculleus and Methanothermobacter likely served as hydrogenotrophic methanogenic partners"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
High-ammonia syntrophic butyrate-oxidizing enrichment MAGs
NCBI BioProject containing the sequencing data and MAG assemblies generated from the 0B butyrate enrichment, YB cultures, and acetate control. |
METAGENOMICS | NCBI_BIOPROJECT | PRJNA1419612 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Does the moderate-quality Candidatus Thermosyntrophaceticus-like MAG2 actively perform syntrophic acetate oxidation in the 0B enrichment, and what is the division of hydrogen versus formate transfer among the MAG1, MAG2, Methanoculleus, and Methanothermobacter MAGs?
The 0B enrichment couples butyrate loss to methane formation, but MAG2 was reconstructed at moderate quality and a complete Wood-Ljungdahl pathway was inferred from a close relative rather than completely annotated in MAG2 itself. All three pairwise assignments and both acetate-branch arrows remain PARTIAL. The single 0B long-term culture is distinct from replicated yeast-extract YB cultures; yeast-extract-free medium is not proof that butyrate was the only available organic carbon. Direct MAG1-to-methanogen carrier provision is another proposed route, not a new demonstrated branch here. MAG9 alternative roles, hydrogen/formate partition, MAG2 activity and partner necessity remain unresolved; isotope tracing, expression and partner perturbations would discriminate them. Below-detection relative abundance is not extinction, calculated free ammonia is not a direct measurement, and archaeal succession is not a demonstrated rate advantage. No complete mechanism expansion is claimed. Non-graph metadata is preserved, not recertified.
Attaches to: ecological_interactions#Syntrophic Butyrate Oxidation by MAG1, ecological_interactions#Syntrophic Acetate Oxidation by MAG2 to Methanoculleus, ecological_interactions#Syntrophic Acetate Oxidation by MAG2 to Methanothermobacter
1 evidence item(s)
Owing to the relatively low completeness of MAG2, a complete Wood-Ljungdahl pathway could not be annotated
Documents the main uncertainty around MAG2's acetate-oxidizing role.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Primary publication - high-ammonia thermophilic 0B enrichment
Open-access BMC Microbiology study combining cultivation, 16S rRNA amplicon sequencing, and metagenomics to resolve syntrophic butyrate oxidation under thermophilic high-ammonia conditions. |
OTHER | PMID:42527912 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| High-ammonia biogas origin | elevated ammonia digestate | N/A |
|
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| Long-term 0B butyrate enrichment | 972 days and 8 degradation cycles | N/A |
|
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| Thermophilic static dark incubation | 51 +/- 1 C | degrees Celsius |
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Growth Media
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