A defined thermophilic anaerobic two-member syntrophic coculture in which Thermacetogenium phaeum strain PB oxidizes acetate using the reversible Wood-Ljungdahl/CO dehydrogenase-acetyl-CoA pathway, while Methanothermobacter thermautotrophicus strain TM consumes reduced products through hydrogenotrophic methanogenesis. This model system is relevant to anaerobic digestion and methane cycling because acetate oxidation is coupled to methane formation under low hydrogen partial pressure.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Thermacetogenium phaeum PB — ontology label: Thermacetogenium phaeum DSM 12270 | NCBITaxon:1089553 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
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N/A |
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| Methanothermobacter thermautotrophicus TM — ontology label: Methanothermobacter thermautotrophicus | NCBITaxon:145262 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
CROSS_FEEDER
|
N/A |
|
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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.
Syntrophic Acetate Oxidation by Thermacetogenium
SYNTROPHYT. phaeum PB oxidizes acetate in the studied syntrophic coculture with M. thermautotrophicus TM. Enzyme activities and substrate-switch experiments support reversible use of the CO dehydrogenase/acetyl-CoA (Wood-Ljungdahl) pathway. Removal of reduced products supports acetate oxidation; this does not assert obligate partnership on other substrates, since T. phaeum also grows acetogenically in pure culture. Hydrogen and formate are extracellular electron-carrier candidates, not a claim that intracellular cofactors are passed between cells. The detailed formate-linked energy-conservation mechanism remains a model.
Source Taxon: Thermacetogenium phaeum PB
Target Taxon: Methanothermobacter thermautotrophicus TM
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)
Biological Processes:
- acetate catabolic process (GO:0045733 · PathwayMech)
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Acetate oxidation by T. phaeum supplies reduced products for the methanogenic partner, coupling acetate conversion to methane formation. Hydrogen consumption is supported by the TM/PB coculture experiments; PARTIAL for the partition of electron flow between hydrogen and formate and the specific formate-producing energy-conservation model. This is not direct acetate utilization by the methanogen.
Evidence
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PMID:15866934 - SUPPORT (IN_VITRO)"oxidized acetate rapidly"
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PMID:15866934 - SUPPORT (IN_VITRO)"CO dehydrogenase/acetyl-CoA pathway reversibly"
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PMID:31849917 - PARTIAL (IN_VITRO)"yielding formate as reduced product"
Hydrogenotrophic Methanogenesis by Methanothermobacter
SYNTROPHYM. thermautotrophicus TM consumes hydrogen during acetate-fed coculture with T. phaeum PB, supporting product removal and methane formation. The 2002 TM/PB experiment maintained 20 to 80 Pa hydrogen and detected mcr/MRI rather than mrt/MRII expression in coculture; other assayed methanogenesis genes were expressed in both culture modes. This is not a universal activation of all methanogenesis genes or evidence of obligate dependence on PB. TM can also use formate; the hydrogenotrophic designation does not exclude formate-supported electron transfer. The separate DeltaH/butyrate coculture is not the PB/TM system.
Source Taxon: Methanothermobacter thermautotrophicus TM
Target Taxon: Thermacetogenium phaeum PB
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
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PMID:11872465 - SUPPORT (IN_VITRO)"thermophilic hydrogen-utilizing methanogen"
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PMID:11872465 - SUPPORT (IN_VITRO)"hydrogen partial pressure was constantly kept very low"
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PMID:11872465 - SUPPORT (IN_VITRO)"only the mcr gene"
Formate-Linked Syntrophic Electron Transfer
CROSS_FEEDINGPARTIAL: formate involvement in T. phaeum PB to M. thermautotrophicus TM electron transfer is supported by the partner-comparison literature discussed in the 2019 study, not dismissed as a genomic conjecture. The 2019 proteome and enzyme assays support a quinone-linked formate dehydrogenase and methyl-THF oxidation machinery. HYPOTHESIZED: their coupling through reverse electron transport, an ATP-supported proton gradient and ATP-independent acetate activation. Proton-gradient coupling and physiological acetate reduction were not demonstrated there. Neither the exact in vivo formate flux nor its fraction of total transferred electrons is established by these enzyme assays.
Source Taxon: Thermacetogenium phaeum PB
Target Taxon: Methanothermobacter thermautotrophicus TM
Metabolites: formate (CHEBI:15740 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
PARTIAL: formate produced by T. phaeum can supply reducing equivalents to the formate-utilizing TM partner for methanogenesis, while removal helps maintain favorable acetate oxidation. HYPOTHESIZED for the specific proton-coupled production mechanism; this arrow does not establish its in vivo flux or convert formate utilization into hydrogen-only metabolism.
Evidence
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PMID:31849917 - PARTIAL (IN_VITRO)"transferred to the methanogenic partner"
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PMID:31849917 - SUPPORT (IN_VITRO)"quinone-dependent formate dehydrogenase"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Thermacetogenium phaeum DSM 12270 genome BioProject
Genome sequencing project for T. phaeum DSM 12270 strain PB, the bacterial member of this syntrophic coculture. |
GENOMICS | NCBI_BIOPROJECT | PRJNA168373 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How much electron transfer uses formate, and which proton-coupled steps operate during PB/TM acetate oxidation?
The formate-transfer interpretation is supported, but enzyme/proteome results do not establish the complete energy budget or in vivo electron partition. The 2019 study explicitly leaves proton coupling and physiological acetate reduction unresolved. Preserve these distinctions when interpreting the two incoming methanogenesis arrows. Non-graph assay-condition followup remains issue #1890.
Attaches to: ecological_interactions#Syntrophic Acetate Oxidation by Thermacetogenium, ecological_interactions#Hydrogenotrophic Methanogenesis by Methanothermobacter, ecological_interactions#Formate-Linked Syntrophic Electron Transfer
1 evidence item(s)
transferred to the methanogenic partner
Authors interpret formate as a transferred product; the quoted conclusion does not itself measure interspecies flux or validate all proposed coupling steps.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Exact-system pathway publication - T. phaeum and M. thermautotrophicus
Primary publication describing acetate oxidation and acetate formation by the T. phaeum and M. thermautotrophicus syntrophic coculture. |
OTHER | PMID:15866934 |
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Exact-system methanogenesis expression publication
Publication reporting methanogenesis gene expression in M. thermoautotrophicus strain TM cocultured with T. phaeum strain PB. |
OTHER | PMID:11872465 |
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Exact-system energy-conservation publication
Follow-up publication on energy-conserving enzyme systems in T. phaeum during syntrophic acetate oxidation with methanogens. |
OTHER | PMID:31849917 |
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Thermacetogenium phaeum type strain publication
Taxonomic publication for T. phaeum PB/DSM 12270 and its syntrophic acetate-oxidizing phenotype. |
OTHER | PMID:10939667 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Thermophilic temperature | 55 to 58 | degrees Celsius |
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| Anaerobic methanogenic condition | anaerobic methanogenic coculture | N/A |
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| Low hydrogen partial pressure | 20 to 80 | Pa |
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| Acetate substrate | acetate | N/A |
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Growth Media
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