A defined synthetic methanotroph-cyanobacterium coculture developed at Pacific Northwest National Laboratory for simultaneous use of methane and carbon dioxide gas feedstocks. The methanotrophic bacterium Methylomicrobium alcaliphilum 20z, currently represented by NCBI as Methylotuvimicrobium alcaliphilum 20Z, is coupled to the cyanobacterium Synechococcus PCC 7002, currently represented by NCBI as Picosynechococcus sp. PCC 7002. The coculture converts CH4 and CO2 into microbial biomass through oxygenic photosynthesis-driven O2 supply to the methanotroph and respiratory CO2 supply to the photoautotroph, with follow-up work using the same species pair for quantitative coculture characterization.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Methylomicrobium alcaliphilum 20z — ontology label: Methylotuvimicrobium alcaliphilum 20Z | NCBITaxon:1091494 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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ABUNDANT |
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| Synechococcus PCC 7002 — ontology label: Picosynechococcus sp. PCC 7002 | NCBITaxon:32049 · 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.
Photosynthetic O2 Support for Methane Oxidation
Synechococcus PCC 7002 supplies photosynthetic O2 supporting aerobic methane oxidation by M. alcaliphilum 20z. The 2017 continuous synthetic-natural-gas process reached steady state under coupled light and O2 limitations, with an O2-depleted reactor and no fed CH4/O2 mixture. Oxygen depletion does not imply anaerobic methane oxidation; directed support alone does not establish reciprocal fitness benefit.
Source Taxon: Synechococcus PCC 7002
Target Taxon: Methylomicrobium alcaliphilum 20z
Metabolites: oxygen (CHEBI:15379 · MediaIngredientMech · CMMMech), methane (CHEBI:16183 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- methane metabolic process (GO:0015947 · PathwayMech)
Photosynthetic oxygen production supports aerobic methane oxidation and thereby positive whole-coculture conversion of gas carbon into biomass. This physiological coupling is retained without requiring an independently measured respiratory-CO2 transfer rate or reciprocal growth enhancement.
Evidence
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PMID:28092828 - SUPPORT (IN_VITRO)"via oxygenic photosynthesis"
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PMID:28092828 - SUPPORT (IN_VITRO)"does not require CH4/O2 mixtures to be fed"
CO2 Utilization by Cyanobacterial Partner
CROSS_FEEDINGPARTIAL - the cyanobacterium uses inorganic carbon from the supplied gas/medium and can use CO2 released by methanotroph respiration. The 20ZR/PCC7002 follow-up supports this exchange interpretation using an experimental-computational mass balance, not independently measured partner-specific CO2 flux. The respiratory contribution is inferred from methane uptake and growth stoichiometry; it is not separately isotope-resolved from supplied inorganic carbon.
Source Taxon: Methylomicrobium alcaliphilum 20z
Target Taxon: Synechococcus PCC 7002
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech)
Biological Processes:
- carbon fixation (GO:0015977 · PathwayMech)
- photosynthesis (GO:0015979 · PathwayMech)
PARTIAL - cyanobacterial carbon assimilation contributes to coculture biomass, with respiratory CO2 recycling supported by the follow-up mass-balance interpretation. The individual rates are stoichiometric estimates, so this arrow does not establish the exact recycled fraction or mutually enhanced growth.
Evidence
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PMID:28092828 - PARTIAL (IN_VITRO)"robust growth on diverse gas mixtures"
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PMID:33064298 - PARTIAL (IN_VITRO)"individual consumption and production rates of O2 and CO2"
Methane and Carbon Dioxide Conversion to Biomass
The 20z/PCC7002 coculture converts methane and carbon dioxide from tested gas feedstocks into microbial biomass. This positive system endpoint is distinct from a demonstrated increase in each partner's fitness. The quantitative follow-up uses the 20ZR derivative with PCC7002; its mass-balance estimates should not be treated as direct exchange measurements in the original continuous reactor.
Participating Taxa: Methylomicrobium alcaliphilum 20z, Synechococcus PCC 7002
Metabolites: methane (CHEBI:16183 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), oxygen (CHEBI:15379 · MediaIngredientMech · CMMMech)
Biological Processes:
- methane metabolic process (GO:0015947 · PathwayMech)
- photosynthesis (GO:0015979 · PathwayMech)
Evidence
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PMID:28092828 - SUPPORT (IN_VITRO)"converts greenhouse gasses, CH4 and CO2, into microbial biomass"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How much cyanobacterial carbon derives from methanotroph respiration under each gas regime?
Keep positive photosynthetic O2 support and gas-to-biomass conversion. The 2017 exact-pair abstract was read; PNNL PDF download returned 403, so its full controls are not certified. Public PMID:33064298 accepted manuscript and included supplement text were read; equation pages 10-11 visually checked. Organism-specific O2/CO2 rates derive from total gas changes, TIC and growth coefficients, with dissolved O2 neglected. Flow cytometry/OD checks support biomass estimation, not independent gas-flux validation. Its saltwater 20ZR/PCC7002 pair differs from the separate M. capsulatus/C. sorokiniana pair; the latter's oxygen-limited inoculum response must not be imported here. #1609 repairs graph wording; #1612 keeps non-graph measurement/protocol claims open.
Attaches to: ecological_interactions#Photosynthetic O2 Support for Methane Oxidation, ecological_interactions#CO2 Utilization by Cyanobacterial Partner, ecological_interactions#Methane and Carbon Dioxide Conversion to Biomass
External Resources
| Name | Repository | Resource ID |
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Exact-system primary publication - gas feedstock coculture
Primary publication reporting the M. alcaliphilum 20z and Synechococcus PCC 7002 coculture for simultaneous methane and carbon dioxide utilization. |
OTHER | PMID:28092828 |
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Exact species-pair follow-up publication - quantitative characterization
Follow-up publication using the same Methylomicrobium alcaliphilum and Synechococcus PCC 7002 species composition, with a 20ZR methanotroph derivative, for quantitative measurement of individual biomass and O2/CO2 rates. |
OTHER | PMID:33064298 |
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Environmental Factors
| Factor | Value | Unit |
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| Gas feedstock composition | diverse gas mixtures ranging from biogas to natural-gas feedstock analogs | N/A |
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| Light and O2 limitation | coupled light and O2 limitations | N/A |
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Growth Media
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