A designed two-member light-driven microbial mutualism pairing sucrose-exporting cscB Synechococcus elongatus PCC 7942 with the diazotroph Azotobacter vinelandii AV3. The engineered cyanobacterium fixes carbon under illumination and exports sucrose, while A. vinelandii fixes nitrogen and can produce industrially relevant biopolymers such as polyhydroxybutyrate and alginate. The coculture was engineered to grow without added fixed carbon or fixed nitrogen and is relevant to DOE interests in photosynthetic bioproduction, carbon utilization, and nitrogen self-sufficient synthetic consortia.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Synechococcus elongatus PCC 7942 cscB — ontology label: Synechococcus elongatus PCC 7942 = FACHB-805 | NCBITaxon:1140 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
CROSS_FEEDER
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DOMINANT |
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| Azotobacter vinelandii AV3 — ontology label: Azotobacter vinelandii | NCBITaxon:354 · TaxonMech · TraitMech |
CROSS_FEEDER
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COMMON |
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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 Sucrose Transfer To Azotobacter
CROSS_FEEDINGThe engineered cscB S. elongatus/AV3 A. vinelandii coculture required a sucrose-exporting cyanobacterium and grew without added fixed carbon or nitrogen. This supports the existing photosynthetic carbon-supply direction. The initial glutamate-supplemented experiments are a distinct context; the reviewed abstract does not resolve transfer rates or detailed transport.
Source Taxon: Synechococcus elongatus PCC 7942 cscB
Target Taxon: Azotobacter vinelandii AV3
Metabolites: carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech), sucrose (CHEBI:17992 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- sucrose biosynthetic process (GO:0005986 · PathwayMech)
HYPOTHESIZED/PARTIAL: cyanobacterial carbon supply supports the productive coculture and is proposed to provide carbon for PHB. The abstract establishes exporter-dependent growth and PHB production, not direct carbon tracing into PHB or isolated control of its yield.
Evidence
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PMID:27232890 - SUPPORT (IN_VITRO)"cannot grow in the absence of a sucrose-exporting S. elongatus"
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PMID:27232890 - SUPPORT (IN_VITRO)"We investigate the growth of a photosynthetic cyanobacterium"
Diazotrophic Nitrogen Support
MUTUALISMThe diazotrophic AV3 partner provides nitrogen-fixation capacity in the engineered mutualism that grows without added fixed carbon or nitrogen, whereas neither member grows alone under that omission. Preserve this growth-context mutualism without specifying an unreported exported nitrogen compound, transfer rate or nitrogen-dependent change in PHB yield.
Source Taxon: Azotobacter vinelandii AV3
Target Taxon: Synechococcus elongatus PCC 7942 cscB
Metabolites: nitrogen (CHEBI:17997 · MediaIngredientMech · CMMMech)
Biological Processes:
- nitrogen fixation (GO:0009399 · PathwayMech)
HYPOTHESIZED/PARTIAL: diazotrophic support could enable growth of the PHB-producing coculture under fixed-nitrogen omission. The abstract does not isolate nitrogen supply as the mediator of a PHB-production change or establish the exact PHB assay conditions.
Evidence
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PMID:27232890 - SUPPORT (IN_VITRO)"a diazotroph, Azotobacter vinelandii"
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PMID:27232890 - SUPPORT (IN_VITRO)"neither organism can grow alone without fixed carbon or nitrogen"
Light-Driven PHB Production
The designed coculture was demonstrated to produce PHB. This is a productive community endpoint, not independent evidence of reciprocal fitness or direct photosynthetic flux. The abstract names alginate as a potential product, not demonstrated production, and does not supply the PHB assay conditions or quantify carbon/nitrogen mediation.
Participating Taxa: Synechococcus elongatus PCC 7942 cscB, Azotobacter vinelandii AV3
Metabolites: poly(3-hydroxybutyrate) (CHEBI:53389 · MediaIngredientMech · CMMMech)
Evidence
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PMID:27232890 - SUPPORT (IN_VITRO)"We demonstrate the ability of the coculture to produce PHB in this work."
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How do carbon and nitrogen provision contribute to the demonstrated PHB outcome?
The independently retrieved primary abstract distinguishes initial glutamate studies from the engineered carbon/nitrogen-omission mutualism. It supports exporter-dependent growth, failure of either partner alone under omission and PHB production. It does not specify a transferred nitrogen species, fluxes or the precise PHB assay conditions. Full article and supplements were not retrieved in this bounded review; no absence claim is made. Alginate remains a proposed capability, not a measured product.
Attaches to: ecological_interactions#Photosynthetic Sucrose Transfer To Azotobacter, ecological_interactions#Diazotrophic Nitrogen Support, ecological_interactions#Light-Driven PHB Production
1 evidence item(s)
From initial studies of the coculture grown in media with glutamate, we proposed a model of cross-feeding between these organisms.
Initial supplemented-condition model must not be conflated with the later engineered omission experiment.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Exact-system primary publication - A. vinelandii/S. elongatus photoproduction coculture
Primary publication reporting the designed A. vinelandii AV3 and cscB S. elongatus mutualism for PHB photoproduction. |
OTHER | PMID:27232890 |
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Exact-system DOI landing page
DOI landing page for the same ACS Synthetic Biology exact-system publication. |
OTHER | doi:10.1021/acssynbio.6b00107 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Illumination | sunlight or laboratory illumination | N/A |
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| Absence of fixed carbon and nitrogen | no added fixed carbon or fixed nitrogen | N/A |
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| Trace metals | trace metals as inorganic input | N/A |
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Growth Media
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