A defined anaerobic syntrophic coculture in which Syntrophus gentianae degrades benzoate in association with the methanogen Methanospirillum hungatei. The system is relevant to DOE anaerobic carbon cycling, wastewater digestion, and aromatic-compound bioconversion because it links methanogenic benzoate degradation, thermodynamic thresholds, acetate inhibition, and methane formation in a tractable two-member community.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Syntrophus gentianae | NCBITaxon:43775 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
|
N/A |
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| Methanospirillum hungatei | NCBITaxon:2203 · 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.
Methanogenic Benzoate Degradation
SYNTROPHYSyntrophus gentianae degrades benzoate in coculture with Methanospirillum hungatei, yielding acetate and methane under methanogenic conditions.
Source Taxon: Syntrophus gentianae
Target Taxon: Methanospirillum hungatei
Metabolites: benzoate (CHEBI:16150 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- benzoate metabolic process (GO:0018874 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
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PMID:33657722 - SUPPORT (IN_VITRO)"Growing cocultures of Syntrophus gentianae with Methanospirillum hungatei degraded benzoate"
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PMID:33657722 - SUPPORT (IN_VITRO)"degraded benzoate to CH4 and acetate"
Minimum Energy Threshold for Syntrophic Growth
During growth of the methanogenic coculture, calculated free energy available to S. gentianae was -50 to -55 kJ per mol benzoate. The authors inferred an approximate -45 kJ/mol requirement for growth and energy conservation. This is a condition-dependent energetic constraint of the fermenter, not a second partner-directed syntrophy event or an invariant value for every suspension or perturbation.
Source Taxon: Syntrophus gentianae
Metabolites: benzoate (CHEBI:16150 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
- benzoate metabolic process (GO:0018874 · PathwayMech)
DIRECTLY IMPLIED: the fermenter must conserve sufficient energy to sustain growth-associated benzoate conversion. The observed endpoint correlates with residual substrate and calculated free energy; the inferred approximate growth threshold is not an independently manipulated universal constant.
Evidence
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PMID:33657722 - SUPPORT (IN_VITRO)"change of free energy available for Syntrophus gentianae ranged between -50 and -55 kJ mol-1"
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PMID:33657722 - SUPPORT (IN_VITRO)"minimum energy required for growth and energy conservation of the benzoate-fermenting bacterium S. gentianae is approximately -45 kJ (mol benzoate)-1"
Product Inhibition of Benzoate Degradation
Accumulated hydrogen and acetate constrain methanogenic benzoate degradation thermodynamically. Acetate and separately added propionate also lower degradation rate; propionate is not identified as a benzoate product here. These are metabolite and energetic constraints on the coculture, not competition between S. gentianae and M. hungatei. Rescue with added sulfate reducers or Methanosaeta changes community composition and is not an unmodified two-member outcome.
Participating Taxa: Syntrophus gentianae, Methanospirillum hungatei
Metabolites: acetate (CHEBI:30089 · MediaIngredientMech · CMMMech), dihydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)
Biological Processes:
- benzoate metabolic process (GO:0018874 · PathwayMech)
Product accumulation changes the free energy available to the fermenter, bringing growth-associated benzoate conversion toward its energetic limit. Acetate also partly uncouples substrate degradation from energy conservation, so this does not assert that product addition changes a fixed intrinsic threshold.
Evidence
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PMID:33657722 - SUPPORT (IN_VITRO)"Accumulated acetate proved to be thermodynamically inhibitory"
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PMID:33657722 - SUPPORT (IN_VITRO)"Addition of acetate or propionate to benzoate-degrading cocultures also lowered the rate"
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PMID:33657722 - SUPPORT (IN_VITRO)"Both hydrogen and acetate inhibit benzoate degradation thermodynamically"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Syntrophus gentianae DSM 8423 genome assembly
Genome assembly for S. gentianae DSM 8423/HQG1, the benzoate-degrading bacterial species. |
GENOMICS | OTHER | GCA_900109885.1 |
|
Syntrophus gentianae DSM 8423 IMG genome
JGI IMG genome resource for S. gentianae DSM 8423. |
GENOMICS | JGI_IMG | 2634166346 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How do energetic limits vary with growth, dense suspensions and added partners?
The primary abstract distinguishes growing cocultures from cell suspensions and inhibitor or added-partner treatments. Its approximate -45 kJ/mol growth requirement is not a universal endpoint. The graph preserves product-inhibition constraints without encoding interspecies competition or treating expanded-community rescue as the original pair.
Attaches to: ecological_interactions#Minimum Energy Threshold for Syntrophic Growth, ecological_interactions#Product Inhibition of Benzoate Degradation
1 evidence item(s)
acetate also partly uncouples substrate degradation from energy conservation
This is an energetic constraint rather than a competition phenotype.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Exact-system primary publication - S. gentianae and M. hungatei benzoate coculture
Primary publication reporting energetics of methanogenic benzoate degradation by the S. gentianae and M. hungatei coculture. |
OTHER | PMID:33657722 |
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NCBI Taxonomy - Syntrophus gentianae
NCBI Taxonomy record for Syntrophus gentianae. |
OTHER | NCBITaxon:43775 |
|
NCBI Taxonomy - Methanospirillum hungatei
NCBI Taxonomy record for Methanospirillum hungatei. |
OTHER | NCBITaxon:2203 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Methanogenic anaerobic condition | methanogenic coculture | N/A |
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| Residual benzoate threshold | 0.2 | mM |
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| Acetate and hydrogen inhibition | thermodynamic inhibition | N/A |
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| Hydrogen-scavenging sulfate reducer perturbation | BES-inhibited methanogenic coculture plus H2-oxidizing sulfate reducer | N/A |
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Growth Media
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