A defined host-associated gnotobiotic mouse community used to test archaeal-bacterial mutualism in the gut. Germ-free mice were colonized with Bacteroides thetaiotaomicron with or without Methanobrevibacter smithii or Desulfovibrio piger, revealing a specific interaction in which M. smithii redirects B. thetaiotaomicron toward dietary fructan fermentation to acetate while using B. thetaiotaomicron formate for methanogenesis.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Bacteroides thetaiotaomicron | NCBITaxon:818 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
CROSS_FEEDER
|
N/A |
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| Methanobrevibacter smithii | NCBITaxon:2173 · 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.
Inferred Formate Transfer To Methanogenesis
SYNTROPHYPARTIAL - the source infers that B. thetaiotaomicron-derived formate supports M. smithii methanogenesis from in-vitro formate consumption and in-vivo bacterial/archaeal transcription. Cecal formate concentration did not differ significantly. SYNTROPHY represents the proposed product-removal mechanism, not a directly resolved donor-specific flux or proof of obligacy.
Source Taxon: Bacteroides thetaiotaomicron
Target Taxon: Methanobrevibacter smithii
Metabolites: formate (CHEBI:15740 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanogenesis (GO:0015948 · PathwayMech)
PARTIAL - methanogen consumption of bacterial formate could relieve a fermentation-product constraint and contribute to higher colonization of both partners. Formate-specific necessity and its contribution relative to hydrogen were not resolved by the inspected main-paper measurements.
Evidence
-
PMID:16782812 - PARTIAL (IN_VIVO)"B. thetaiotaomicron-derived formate is used by M. smithii for methanogenesis"
Methanogen-Directed Fructan Fermentation
SYNTROPHYM. smithii biassociation increased dietary-fructan utilization and acetate concentration, with bacterial transcriptional and redox changes unlike the D. piger comparator. PARTIAL - product removal provides the source's syntrophic explanation; the specific necessary sink was not isolated.
Participating Taxa: Methanobrevibacter smithii, Bacteroides thetaiotaomicron
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
PARTIAL - enhanced dietary-fructan fermentation could supply energy supporting bacterial expansion within the mutually beneficial biassociation. The metabolic shifts and higher colonization are measured, but selective pathway mediation was not established by their co-occurrence.
Evidence
-
PMID:16782812 - SUPPORT (IN_VIVO)"M. smithii directs B. thetaiotaomicron to focus on fermentation of dietary fructans to acetate"
Biassociation Enhances Colonization Density
MUTUALISMCocolonization with M. smithii and B. thetaiotaomicron increased representation of both species in the distal intestines of gnotobiotic mice relative to monoassociated controls.
Participating Taxa: Methanobrevibacter smithii, Bacteroides thetaiotaomicron
Biological Processes:
- biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
-
PMID:16782812 - SUPPORT (IN_VIVO)"enhances the representation of both species in the distal intestines of gnotobiotic mice"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Methanobrevibacter smithii gene sequences
M. smithii gene sequence accession reported with the gnotobiotic mutualism study. |
GENOMICS | OTHER | DQ419923 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How much do formate and hydrogen removal contribute to each partner's colonization benefit?
Paired abundance increases support mutualism. Main-paper formate consumption/transcripts, fructan depletion and fermentation pools support a mechanistic model, not donor-specific in-vivo transfer or necessary/sufficient mediation. Labeled analytical internal standards are not tracer-fed flux experiments. Supplementary methods, tables, figures and underlying data remain unread.
Attaches to: ecological_interactions#Inferred Formate Transfer To Methanogenesis, ecological_interactions#Methanogen-Directed Fructan Fermentation, ecological_interactions#Biassociation Enhances Colonization Density
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| germ-free mouse host | Germ-free mice were colonized with defined gut organisms. | N/A |
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| dietary polysaccharides and fructans | B. thetaiotaomicron consumed dietary polysaccharides, with M. smithii directing fructan fermentation. | N/A |
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Growth Media
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