A defined aerobic methane-fed laboratory coculture pairing the marine methanotroph Methylocaldum marinum S8 with the facultative methylotroph Methyloceanibacter caenitepidi Gela4. M. marinum S8 oxidizes methane and supports syntrophic growth of M. caenitepidi Gela4 on methane-derived carbon. Transcriptome and chemical analyses indicate that acetate, rather than methanol alone, is likely a major cross-fed carbon source in this model methanotroph-methylotroph community.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Methylocaldum marinum S8 — ontology label: Methylocaldum marinum | NCBITaxon:1432792 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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N/A |
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| Methyloceanibacter caenitepidi Gela4 — ontology label: Methyloceanibacter caenitepidi | NCBITaxon:1384459 · TaxonMech · TraitMech |
CROSS_FEEDER
SECONDARY_FERMENTER
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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.
Methane-Derived Carbon Cross-Feeding
CROSS_FEEDINGM. marinum S8 supports growth of M. caenitepidi Gela4 with methane supplied as the sole added carbon source after washed inocula. Acetate is a source-supported candidate cross-fed compound: concentrations, transcript profiles and acetate-grown reference qRT-PCR are consistent with it. These results do not quantify donor-to-recipient acetate flux or exclude methanol turnover.
Source Taxon: Methylocaldum marinum S8
Target Taxon: Methyloceanibacter caenitepidi Gela4
Metabolites: methane (CHEBI:16183 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- methane metabolic process (GO:0015947 · PathwayMech)
- acetate metabolic process (GO:0006083 · PathwayMech)
HYPOTHESIZED - a change in available methanotroph-derived carbon could drive the observed Gela4 transcript response. The main RNA-seq comparison changes both partner presence and supplied carbon source; acetate reference qRT-PCR supports the interpretation without selectively identifying the cross-fed inducer.
PARTIAL - S8-derived carbon supports the observed Gela4 growth in methane-fed coculture. Acetate is a plausible mediator, but its share versus methanol or other metabolites is unresolved; this is not evidence of obligatory mutual dependence.
Evidence
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PMID:30870453 - SUPPORT (IN_VITRO)"cross-feeding on methane-derived carbon"
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PMID:30870453 - PARTIAL (IN_VITRO)"organic compound other than methanol, possibly acetate"
Methylotroph Growth in Methane-Fed Coculture
Gela4 grew in methane-fed S8 coculture, with a reported specific growth rate of 0.02/h versus 0.03/h in methanol-grown pure culture. Positive growth is preserved; the different substrates make that comparison unsuitable for claiming growth enhancement. Methanol below 310 nM does not rule out low-concentration, high-turnover cross-feeding, explicitly acknowledged by the authors. Acetate remains a candidate major substrate.
Source Taxon: Methylocaldum marinum S8
Target Taxon: Methyloceanibacter caenitepidi Gela4
Metabolites: methane (CHEBI:16183 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Evidence
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PMID:30870453 - SUPPORT (IN_VITRO)"Methyloceanibacter caenitepidi Gela4, which grows syntrophically with the methanotroph, Methylocaldum marinum S8"
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PMID:30870453 - PARTIAL (IN_VITRO)"organic compound other than methanol, possibly acetate, might be the major carbon source for M. caenitepidi Gela4 cross-fed by M. marinum S8"
Gela4 Carbon-Metabolism Response in Coculture
Relative to methanol-grown Gela4 monoculture, methane-fed S8 coculture showed serine-pathway downregulation and TCA/acetyl-CoA-associated upregulation, including acsA log2FC 3.57. Acetate reached <15.6 micromol/L in S8 culture and <12.4 micromol/L in coculture; methanol was below 310 nM. Acetate-grown reference qRT-PCR supported the interpretation, with late-phase coculture acsA/hpr significantly higher than the methanol control, whereas the early-phase difference was not significant. These are measured concentration and expression results, not direct acetate transfer or proof of methanol independence.
Source Taxon: Methylocaldum marinum S8
Target Taxon: Methyloceanibacter caenitepidi Gela4
Metabolites: methanol (CHEBI:17790 · MediaIngredientMech · CMMMech), acetate (CHEBI:30089 · MediaIngredientMech · CMMMech)
Biological Processes:
- methanol metabolic process (GO:0015945 · PathwayMech)
- acetate metabolic process (GO:0006083 · PathwayMech)
Evidence
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PMID:30870453 - SUPPORT (IN_VITRO)"methanol was below the detection limit"
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PMID:30870453 - SUPPORT (IN_VITRO)"acetyl-CoA synthetase, were upregulated"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
M. caenitepidi Gela4 complete genome
BioProject for the complete genome of the Gela4 methylotrophic partner used in the coculture. |
GENOMICS | NCBI_BIOPROJECT | PRJDB3104 |
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M. caenitepidi Gela4 and M. marinum S8 RNA-seq dataset
DDBJ Sequence Read Archive RNA-seq dataset comparing Gela4 pure culture and methane-fed Gela4/S8 coculture conditions. |
METATRANSCRIPTOMICS | OTHER | DRA006072 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN What fractions of recipient carbon come from acetate, methanol and other S8 products?
Retain positive growth and the authors' acetate interpretation with two qualified existing arrows. Main RNA-seq contrasts methanol monoculture with methane coculture; partner and substrate change together. Acetate-reference qRT-PCR adds support but does not identify transferred carbon by itself. The paper expressly allows low-concentration high-turnover methanol. Main text, captions and Tables 1-2 were read; raw RNA-seq, supplements and figure pixels were not audited. #1604 repairs the graph; methanol ingredient wording and other non-graph fields remain #1606.
Attaches to: ecological_interactions#Methane-Derived Carbon Cross-Feeding, ecological_interactions#Methylotroph Growth in Methane-Fed Coculture, ecological_interactions#Gela4 Carbon-Metabolism Response in Coculture
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
Exact-system publication - Methylocaldum/Methyloceanibacter cross-feeding
Primary publication reporting the exact M. marinum S8 and M. caenitepidi Gela4 methane-fed coculture, RNA-seq response, and likely acetate-mediated cross-feeding. |
OTHER | PMID:30870453 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Methane and oxygen availability | methane/air headspace, 20:80 v/v | N/A |
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Growth Media
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