A defined hyperthermophilic bacterial-archaeal coculture in which Thermotoga maritima MSB8 ferments organic substrates and transfers hydrogen to the hydrogenotrophic methanogen historically reported as Methanococcus jannaschii, now represented by NCBI as Methanocaldococcus jannaschii DSM 2661. The coculture is relevant to DOE bioenergy and subsurface biogeochemistry because it links high-temperature fermentation, interspecies hydrogen transfer, cell aggregation, and methane formation in an experimentally tractable system.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Thermotoga maritima MSB8 | NCBITaxon:243274 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
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N/A |
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| Methanocaldococcus jannaschii DSM 2661 | NCBITaxon:243232 · TaxonMech · TraitMech |
SYNTROPHIC_PARTNER
CROSS_FEEDER
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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.
Interspecies Hydrogen Transfer
SYNTROPHYT. maritima produces hydrogen during fermentation, and hydrogen consumption by M. jannaschii supports methanogenesis while relieving bacterial product inhibition. The 1997 study reported a tenfold bacterial density increase at 85 C and methanogen growth without external H2/CO2. The separate 2006 study reported a three- to fivefold density increase under its own conditions. These are assay-specific effects, not a single universal fold change or obligate mutual dependence under all conditions; T. maritima also grew in monoculture.
Source Taxon: Thermotoga maritima MSB8
Target Taxon: Methanocaldococcus jannaschii DSM 2661
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
PARTIAL: hydrogen removal relieves growth inhibition and enables the higher-density coculture context in which aggregation and altered growth-phase transcription were observed. Hydrogen-removal comparisons support a contribution to physiology, but do not selectively demonstrate mediation of every EPS or transcript response by hydrogen transfer alone. Growth phase, population density and culture/gas-handling conditions remain part of this causal interpretation.
Evidence
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PMID:18636642 - SUPPORT (IN_VITRO)"Cell densities of T. maritima increased 10-fold when cocultured"
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PMID:18636642 - SUPPORT (IN_VITRO)"the methanogen was able to grow in the absence of externally supplied H(2) and CO(2)"
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PMID:16391122 - SUPPORT (IN_VITRO)"Interspecies H2 transfer resulted in three- to fivefold-higher T. maritima cell densities"
Spatially Proximate Methanogenic Coculture
PARTIAL: the 1997 coculture failed to establish when partners were separated by a dialysis membrane, and the methanogen occurred in larger cell sorts. These observations support the importance of spatial proximity in that assay. They do not demonstrate direct cell contact as obligatory, a specific molecular adhesion mechanism, or directional colonization facilitation by the archaeon. Hydrogen transport and metabolic-rate effects were also modeled, rather than all directly measured.
Participating Taxa: Thermotoga maritima MSB8, Methanocaldococcus jannaschii DSM 2661
Metabolites: dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
PARTIAL: proximity can reduce the transport distance for hydrogen from the fermenter to the methanogen, helping establish hydrogen-transfer syntrophy. Failure across a dialysis membrane and size-fraction association support this interpretation, but do not uniquely identify diffusion distance, direct contact or a specific attachment mechanism as the cause.
Evidence
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PMID:18636642 - SUPPORT (IN_VITRO)"could not be established if the two organisms were physically separated"
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PMID:18636642 - PARTIAL (IN_VITRO)"suggesting the importance of spatial proximity"
Coculture-Associated Aggregation and Transcriptome Shift
T. maritima aggregation and transcription changed with growth phase in methanogenic coculture. In the 2006 study, 292 genes changed at least twofold from mid-log to early stationary phase within coculture, versus 24 for that transition within monoculture; these are not 292 genes in a direct coculture-versus-monoculture contrast. EPS-based aggregates were prominent during mid-log growth and diminished during stationary phase. Proposed sigma-factor, ppGpp and EPS-remodeling mechanisms are interpretations, not demonstrated regulatory necessity. The phenotype is not an additional measured metabolite-transfer event from bacterium to archaeon.
Participating Taxa: Thermotoga maritima MSB8, Methanocaldococcus jannaschii DSM 2661
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:16391122 - SUPPORT (IN_VITRO)"292 genes differentially expressed in T. maritima"
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PMID:16391122 - SUPPORT (IN_VITRO)"concomitant formation of exopolysaccharide (EPS)-based cell aggregates"
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PMID:16391122 - SUPPORT (IN_VITRO)"syntrophic interactions can impact the transcriptome of heterotrophs"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
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Thermotoga maritima MSB8 genome BioProject
Genome project for T. maritima MSB8, the fermentative bacterial member. |
GENOMICS | NCBI_BIOPROJECT | PRJNA57723 |
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Methanocaldococcus jannaschii DSM 2661 genome BioProject
Genome project for M. jannaschii DSM 2661, the methanogenic archaeal member. |
GENOMICS | NCBI_BIOPROJECT | PRJNA102 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which proximity and hydrogen-removal effects specifically mediate aggregation and the bacterial transcript response?
Dialysis separation, hydrogen-removal comparisons and growth-phase observations support the existing qualified links, but do not isolate every step. Density-matched and gas-handling-matched comparisons would help distinguish hydrogen transfer from other coculture effects. The 1997 and 2006 assay conditions must remain separate; non-graph metadata followup remains issue #1891.
Attaches to: ecological_interactions#Interspecies Hydrogen Transfer, ecological_interactions#Spatially Proximate Methanogenic Coculture, ecological_interactions#Coculture-Associated Aggregation and Transcriptome Shift
1 evidence item(s)
concomitant formation of exopolysaccharide (EPS)-based cell aggregates
Supports observed EPS-based aggregates accompanying the high-density coculture; specific mediation is not isolated by this quote.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Exact-system hydrogen-transfer publication
Primary publication reporting hydrogen transfer in T. maritima and M. jannaschii hyperthermophilic coculture. |
OTHER | PMID:18636642 |
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Exact-system transcriptome and phenotype publication
Follow-up exact-system publication showing coculture impacts on T. maritima transcriptome and aggregation. |
OTHER | PMID:16391122 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Hyperthermophilic temperature | 85 | degrees C |
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| Anaerobic methanogenic condition | anaerobic | N/A |
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Growth Media
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