A defined anaerobic cellulose-to-methane coculture combining the cellulolytic fermenter Clostridium cellulovorans 743B with the metabolically versatile methanogen Methanosarcina barkeri Fusaro. C. cellulovorans degrades cellulose and produces methanogenesis precursors including hydrogen, formate, and acetate, while M. barkeri consumes those products for methanogenesis. The system is relevant to DOE bioenergy because it is an experimentally tractable model for renewable methane production from cellulosic biomass and for engineering anaerobic biomethanation consortia.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Clostridium cellulovorans 743B | NCBITaxon:573061 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
CROSS_FEEDER
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ABUNDANT |
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| Methanosarcina barkeri Fusaro — ontology label: Methanosarcina barkeri str. Fusaro | NCBITaxon:269797 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
CROSS_FEEDER
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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.
Cellulose Fermentation to Methanogenesis Precursors
CROSS_FEEDINGC. cellulovorans 743B ferments cellulose to hydrogen, formate and acetate that support M. barkeri Fusaro methanogenesis in the tested coculture. Methane production, undetectable hydrogen and transient formate/acetate accumulation followed by depletion support the supply model. Other fermentation products, including butyrate and lactate, are not thereby established as substrates consumed by M. barkeri. Product pools reflect simultaneous production and consumption, not directly resolved partner-specific fluxes.
Source Taxon: Clostridium cellulovorans 743B
Target Taxon: Methanosarcina barkeri Fusaro
Metabolites: cellulose (CHEBI:18246 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
- fermentation (GO:0006113 · PathwayMech)
Cellulose fermentation supplies hydrogen, formate and acetate for coculture-associated methanogenesis by M. barkeri. Exact-pair gas/product profiles and controls support this relationship, but do not resolve each precursor contribution; formate use is condition-dependent rather than evidence that formate alone supports the methanogen.
Evidence
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PMID:28191038 - SUPPORT (IN_VITRO)"produced by C. cellulovorans during cellulose degradation"
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PMID:28191038 - SUPPORT (IN_VITRO)"no H2 was detected in the cocultures throughout the cultivation period"
Coculture-Associated Multi-Substrate Methanogenesis by M. barkeri
SYNTROPHYPARTIAL - coculture methane production and hydrogen, formate and acetate depletion, together with RT-qPCR, support the authors' acetoclastic and CO2-reduction model. M. barkeri did not grow with formate alone after nine months. A mixed-substrate monoculture consumed only about 1.5 mM of 10 mM supplied formate and little acetate, unlike the coculture. The specific formate-linked pathway and each electron contribution remain inferred rather than directly traced. The M. barkeri-to-C. cellulovorans direction represents proposed product-removal feedback to the fermenter, not donation of methanogenesis substrates in that direction.
Source Taxon: Methanosarcina barkeri Fusaro
Target Taxon: Clostridium cellulovorans 743B
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanogenesis (GO:0015948 · PathwayMech)
HYPOTHESIZED - M. barkeri consumption of formate and acetate, together with hydrogen removal and a changed C. cellulovorans fermentation pattern, reduces accumulated acid products and could help stabilize pH and sustain cellulose degradation. The measured coculture outcomes support this model, but do not isolate product removal or pH as the unique mediator. Lower butyrate/lactate pools are not evidence that the methanogen consumed those acids.
Evidence
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PMID:28191038 - PARTIAL (IN_VITRO)"simultaneous utilization of hydrogen, formate, and acetate for methanogenesis"
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PMID:28191038 - PARTIAL (IN_VITRO)"methanogens in both cocultures were able to efficiently utilize"
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PMID:28191038 - SUPPORT (IN_VITRO)"monocultures of M. barkeri were unable to grow with formate alone"
Coculture-Associated Cellulose Degradation and pH Stabilization
Coculturing with M. barkeri increased the extent of cellulose degradation by 13.8% relative to C. cellulovorans monoculture, with a final pH around 6.7 rather than 6.1. These are measured outcomes. HYPOTHESIZED - formate/acetate consumption and altered fermenter production jointly contribute to the smaller pH decline and improved degradation. Butyrate and lactate accumulated to lower levels without net depletion, and C. cellulovorans cell growth was not significantly improved; the reported growth yields were similar. This is not demonstrated reciprocal fitness mutualism or uniquely established pH mediation.
Source Taxon: Methanosarcina barkeri Fusaro
Target Taxon: Clostridium cellulovorans 743B
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellulose catabolic process (GO:0030245 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
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PMID:28191038 - SUPPORT (IN_VITRO)"the presence of methanogens did not result in significant differences in cell growth"
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PMID:28191038 - SUPPORT (IN_VITRO)"degradation was observed in both cocultures"
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PMID:28191038 - PARTIAL (IN_VITRO)"stabilized pH for C. cellulovorans"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which pathways and partner changes mediate coculture-specific formate use and improved cellulose degradation?
PMID:28191038 supports reproducible gas and VFA profiles, formate-only failure, limited mixed-substrate monoculture formate use and altered gene expression. Its conceptual pathways do not directly measure partner flux. Product removal and changed fermenter production can both affect pools and pH. Matched-pH interventions, partner-resolved flux and selective formate-pathway perturbations would separate mediation from association. Increased cellulose degradation did not significantly increase C. cellulovorans cell growth. The distinct M. mazei comparison is not added as a member of this record.
Attaches to: ecological_interactions#Cellulose Fermentation to Methanogenesis Precursors, ecological_interactions#Coculture-Associated Multi-Substrate Methanogenesis by M. barkeri, ecological_interactions#Coculture-Associated Cellulose Degradation and pH Stabilization
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Exact-system primary publication - C. cellulovorans and M. barkeri cellulose-to-methane coculture
Primary open-access publication establishing the C. cellulovorans 743B and M. barkeri Fusaro coculture for direct conversion of cellulose to methane. |
OTHER | PMID:28191038 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Cellulose substrate | cellulose | N/A |
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| Methanogen product utilization | fermentation products consumed by M. barkeri | N/A |
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| pH stabilization | stabilized pH relative to C. cellulovorans monoculture | N/A |
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Growth Media
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