A defined anaerobic syntrophic coculture pairing the propionate-oxidizing bacterium Pelotomaculum thermopropionicum with the hydrogenotrophic methanogen Methanocella conradii. RNA-seq comparisons against monocultures showed coordinated transcriptional shifts in catabolism, methanogenesis, electron bifurcation/confurcation, formate handling, signal transduction, and amino acid exchange. The system is relevant to DOE interests in anaerobic carbon cycling, methane production, syntrophic propionate degradation, and transcriptome-guided bioreactor microbiology.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Pelotomaculum thermopropionicum | NCBITaxon:110500 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
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N/A |
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| Methanocella conradii | NCBITaxon:1175444 · 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.
Propionate Oxidation Coupled to Methanogenesis
SYNTROPHYP. thermopropionicum and M. conradii form a thermodynamically constrained syntrophic pair in which propionate oxidation is coordinated with hydrogenotrophic methanogenesis.
Source Taxon: Pelotomaculum thermopropionicum
Target Taxon: Methanocella conradii
Metabolites: propionate (CHEBI:17272 · MediaIngredientMech · CMMMech), formate (CHEBI:15740 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- propionate metabolic process (GO:0019541 · PathwayMech)
- propionate catabolic process (GO:0019543 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
PARTIAL - the propionate-fed coculture showed increased catabolic and methanogenesis transcripts relative to the monocultures. The source warns that substrate, hydrogen availability and growth rate differ, so this comparison does not isolate the effect of the partner interaction alone.
Evidence
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PMID:30038609 - SUPPORT (IN_VITRO)"thermodynamically-based cooperation between microbial partners"
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PMID:30038609 - SUPPORT (IN_VITRO)"constructed cocultures of propionate-oxidizing Pelotomaculum thermopropionicum and hydrogenotrophic Methanocella conradii"
Catabolism and Methanogenesis Upregulation in Coculture
SYNTROPHYCoculture growth upregulated catabolic genes in both organisms, including methylmalonyl-CoA pathway genes in P. thermopropionicum and methanogenesis genes in M. conradii.
Source Taxon: Pelotomaculum thermopropionicum
Target Taxon: Methanocella conradii
Biological Processes:
- propionate metabolic process (GO:0019541 · PathwayMech)
- methanogenesis (GO:0015948 · PathwayMech)
Evidence
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PMID:30038609 - SUPPORT (IN_VITRO)"both P. thermopropionicum and M. conradii significantly upregulated the expression of genes involved in catabolism"
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PMID:30038609 - SUPPORT (IN_VITRO)"methylmalonyl-CoA pathway in P. thermopropionicum and key genes for methanogenesis in M. conradii"
Formate and Electron Bifurcation Strategy
CROSS_FEEDINGPARTIAL - increased formate-dehydrogenase and putative electron-bifurcation/confurcation transcripts, together with formate and 2-BES perturbations, support the authors' inference that formate contributes to electron transfer and redox balance during syntrophy. These observations do not directly quantify interspecies formate flux or enzyme activity.
Source Taxon: Pelotomaculum thermopropionicum
Target Taxon: Methanocella conradii
Metabolites: formate (CHEBI:15740 · MediaIngredientMech · CMMMech)
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
PARTIAL - formate turnover is inferred to support syntrophic electron transfer. Its effect depends on conditions: adding 20 mM formate immediately halted propionate oxidation, which resumed after formate consumption; adding 5 mM 2-BES abolished propionate oxidation and methane production. The source did not find comparable inhibition after H2/CO2 addition, so this edge does not assert a measured low-H2 requirement in that experiment.
Evidence
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PMID:30038609 - SUPPORT (IN_VITRO)"flavin-based electron bifurcation/confurcation systems in both organisms were also upregulated"
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PMID:30038609 - PARTIAL (IN_VITRO)"formate was produced and utilized by P. thermopropionicum and M. conradii, respectively"
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PMID:30038609 - SUPPORT (IN_VITRO)"The addition of formate halted propionate oxidation and CH4 production immediately"
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PMID:30038609 - SUPPORT (IN_VITRO)"Methane production and propionate oxidation were completely inhibited after the addition of 2-BES"
Signal Transduction and Amino Acid Exchange
MUTUALISMHYPOTHESIZED - RNA-seq changes suggest flagellum-related signaling and amino-acid exchange during syntrophy. The source specifically hypothesizes amino-acid transfer from M. conradii to P. thermopropionicum; transcript changes do not directly demonstrate transfer or a single direction for both signaling and nutrient exchange.
Participating Taxa: Pelotomaculum thermopropionicum, Methanocella conradii
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:30038609 - PARTIAL (IN_VITRO)"flagellum-induced signal transduction and amino acids exchange was upregulated"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Pelotomaculum-Methanocella syntrophic coculture RNA-seq
GEO series for strand-specific RNA-seq comparing P. thermopropionicum and M. conradii monocultures with the syntrophic coculture. |
METATRANSCRIPTOMICS | OTHER | GSE103596 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which transcript changes and exchange routes are causal drivers of the syntrophic phenotype?
PMID:30038609 compares pyruvate-grown bacterial and H2/CO2-grown archaeal monocultures with a propionate-fed coculture at a different growth rate. The authors caution that these differences affect transcription. Parallel catabolic, formate-handling and signaling responses do not establish an ordered causal chain. Amino-acid transfer from M. conradii to P. thermopropionicum is explicitly hypothesized and requires direct transfer or perturbation evidence.
Attaches to: ecological_interactions#Propionate Oxidation Coupled to Methanogenesis, ecological_interactions#Catabolism and Methanogenesis Upregulation in Coculture, ecological_interactions#Formate and Electron Bifurcation Strategy, ecological_interactions#Signal Transduction and Amino Acid Exchange
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Exact-system primary publication - P. thermopropionicum and M. conradii RNA-seq coculture
Primary publication reporting transcriptome shifts in the exact two-member syntrophic coculture. |
OTHER | PMID:30038609 |
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DOI landing page - P. thermopropionicum and M. conradii coculture
DOI landing page for the exact-system RNA-seq publication. |
OTHER | doi:10.3389/fmicb.2018.01551 |
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GEO RNA-seq series GSE103596
Public GEO series for RNA-seq data from monoculture and syntrophic coculture conditions. |
OTHER | GSE103596 |
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NCBI Taxonomy - Pelotomaculum thermopropionicum
NCBI Taxonomy record for Pelotomaculum thermopropionicum. |
OTHER | NCBITaxon:110500 |
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NCBI Taxonomy - Methanocella conradii
NCBI Taxonomy record for Methanocella conradii. |
OTHER | NCBITaxon:1175444 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Anaerobic syntrophic energy limitation | small free-energy sharing | N/A |
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| Coculture versus monoculture comparison | cocultures compared to monocultures | N/A |
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| Formate and BES inhibition | formate and 2-bromoethanesulphonate inhibited syntrophic activity | N/A |
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