A defined thermoacidophilic methanotroph-microalga coculture pairing Methylacidiphilum sp. RTK17.1 with Galdieria sp. RTK37.1 for methane and carbon dioxide valorisation. In methane-fed photobioreactor studies, the methanotroph benefits from oxygen supplied by the extremophilic microalga under low-oxygen conditions, enhancing growth and methane oxidation. Follow-up work showed that this interaction is density-dependent: low initial Methylacidiphilum:Galdieria ratios improve net carbon fixation, whereas elevated methanotroph abundance can impose oxygen competition, causing chlorosis and reduced carbon assimilation.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Methylacidiphilum sp. RTK17.1 — ontology label: Candidatus Methylacidiphilum infernorum | NCBITaxon:511746 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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ABUNDANT |
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| Galdieria sp. RTK37.1 — ontology label: Galdieria sp. | NCBITaxon:2530459 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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ABUNDANT |
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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.
Low-Oxygen Algal O2 Support for Methane Oxidation
Under low initial oxygen, photosynthetic Galdieria sp. RTK37.1 supplies oxygen supporting Methylacidiphilum sp. RTK17.1 growth and methane oxidation. The positive support depends on inoculum proportions and gas supply. This directed benefit does not by itself establish reciprocal carbon donation to the alga or obligatory mutualism.
Source Taxon: Galdieria sp. RTK37.1
Target Taxon: Methylacidiphilum sp. RTK17.1
Metabolites: oxygen (CHEBI:15379 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- methane metabolic process (GO:0015947 · PathwayMech)
Algal oxygen production supports aerobic methane oxidation and contributes to greater whole-coculture net carbon fixation at low methanotroph-to-alga ratios. This is a condition-dependent system benefit, not quantified methanotroph-to-alga carbon transfer.
Evidence
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PMID:41888821 - SUPPORT (IN_VITRO)"oxygen supplied by the extremophilic microalga Galdieria sp. RTK37.1"
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PMID:41888821 - SUPPORT (IN_VITRO)"enhancing growth and methane oxidation"
Biomass-Ratio-Dependent Oxygen Competition
COMPETITIONAt initial Methylacidiphilum:Galdieria biomass ratios >=0.23:1 in low-oxygen methane-fed batches, growth fell 66-100% and net carbon fixation fell 44-62% relative to methane-free controls. Pigment loss, chlorosis and LC-MS-confirmed extracellular coproporphyrin III accompanied oxygen competition. Daily CH4/CO2/O2 replenishment prevented chlorosis. In a separate recovery experiment, methane was removed on day 4 and oxygen was allowed to accumulate without oxygen addition; pigments recovered before growth resumed. Oxygen-dependent HemF inhibition and porphyrin reuptake are proposed molecular explanations, not directly measured enzyme inhibition or transport.
Source Taxon: Methylacidiphilum sp. RTK17.1
Target Taxon: Galdieria sp. RTK37.1
Metabolites: oxygen (CHEBI:15379 · MediaIngredientMech · CMMMech), coproporphyrin III (CHEBI:27609 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
Oxygen competition at high methanotroph abundance suppresses algal activity and decreases whole-coculture carbon fixation, opposing the low-ratio benefit. Ratio and gas interventions support this physiological mechanism; they do not individually establish HemF inhibition, porphyrin reuptake or a universal ratio threshold.
Evidence
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PMID:41888821 - SUPPORT (IN_VITRO)"inhibitory due to oxygen competition"
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PMID:41888821 - SUPPORT (IN_VITRO)"chlorosis and excreted coproporphyrin III"
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PMID:41888821 - SUPPORT (IN_VITRO)"No O2 was added at any point."
Methane-Linked Carbon Valorisation
Methane-fed cocultures at low initial Methylacidiphilum:Galdieria ratios (<0.18:1) showed 17-28% greater net carbon fixation than methane-free controls. This endpoint was calculated from initial/final gas concentrations, pressure and temperature across six days; it is a whole-system carbon balance, not partner-resolved assimilation or proof of CO2 transfer from methanotroph to alga. The maximum measured methane-consumption rate was 0.124 +/- 0.001 mmol/L/h at 0.15:1, where methane was depleted, so it is not an unconstrained rate optimum.
Participating Taxa: Methylacidiphilum sp. RTK17.1, Galdieria sp. RTK37.1
Metabolites: methane (CHEBI:16183 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech)
Biological Processes:
- methane metabolic process (GO:0015947 · PathwayMech)
- carbon fixation (GO:0015977 · PathwayMech)
Evidence
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PMID:41888821 - SUPPORT (IN_VITRO)"greater net carbon fixation"
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PMID:41888821 - SUPPORT (IN_VITRO)"methane-fed photobioreactors relevant to SCP production"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which molecular and partner-resolved processes explain the physiological oxygen trade-off?
Retain the positive oxygen-support and inhibitory competition arrows. Separate daily gas replenishment from day-4 methane removal without added O2. HemF inhibition, porphyrin reuptake and potential metal sequestration remain interpretations; no new molecular arrow is added. Gas-based net fixation is not taxon-resolved carbon donation, and the ratio threshold depends on culture conditions. PMID:41888821 main text and captions were read, not separate supplements or figure pixels. #1602 repairs graph scope; #1606 retains protocol discrepancies, pure-culture formate context and canonical-taxonomy follow-up.
Attaches to: ecological_interactions#Low-Oxygen Algal O2 Support for Methane Oxidation, ecological_interactions#Biomass-Ratio-Dependent Oxygen Competition, ecological_interactions#Methane-Linked Carbon Valorisation
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Exact-system publication - oxygen competition in methane-fed coculture
Publication reporting density-dependent oxygen exchange and oxygen competition in the exact Methylacidiphilum sp. RTK17.1 and Galdieria sp. RTK37.1 coculture. |
OTHER | PMID:41888821 |
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Exact-system publication - single-cell protein cocultivation
Earlier open-access Engineering Microbiology publication using the same Methylacidiphilum sp. RTK17.1 and Galdieria sp. RTK37.1 species-pair composition for single-cell protein production. |
OTHER | doi:10.1016/j.engmic.2025.100229 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Low oxygen availability | low-O2 coculture condition | N/A |
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| Initial partner biomass ratio | low ratios beneficial; elevated methanotroph abundance inhibitory | N/A |
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Growth Media
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