A synthetic, light-driven consortium pairing the cyanobacterium Synechococcus elongatus PCC 7942 (engineered to secrete sucrose via the cscB+ transporter) with Escherichia coli. The cyanobacterium fixes CO2 and exports up to 85% of fixed carbon as sucrose, which supports heterotrophic growth of E. coli. This modular platform enables stable, long-term photosynthetic co-culture for biofuel precursor production and demonstrates a synthetic cross-feeding interaction that persists over days to months.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Synechococcus elongatus PCC 7942 cscB+ — ontology label: Synechococcus elongatus | NCBITaxon:32046 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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N/A |
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| Escherichia coli W delta-cscR — ontology label: Escherichia coli | NCBITaxon:562 · TaxonMech · TraitMech |
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.
Photosynthetic carbon supply to E. coli
CROSS_FEEDINGCscB+ S. elongatus fixes carbon and exports sucrose, but E. coli W and W delta-cscR grew during early batch coculture independently of induced sucrose export. The source infers substantial use of other photosynthates at that stage; their identities, including the proposed extracellular polymers, were not resolved. The earlier 85% carbon-export capability is not a concentration or a measurement of this dyad.
Source Taxon: Synechococcus elongatus PCC 7942 cscB+
Target Taxon: Escherichia coli W delta-cscR
Metabolites: sucrose (CHEBI:17992 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- sucrose biosynthetic process (GO:0005986 · PathwayMech)
Cyanobacterial photosynthate supports E. coli growth. PARTIAL for sucrose-specific mediation: early growth was insensitive to export induction, so that phase cannot be attributed solely to sucrose; later productive cocultures show a sucrose contribution.
Evidence
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PMID:28127397 - SUPPORT (IN_VITRO)"We previously engineered a model cyanobacterium, Synechococcus elongatus PCC 7942, to secrete the bulk of the carbon it fixes as sucrose, a carbohydrate that can be utilized by many other microbes"
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PMID:28127397 - PARTIAL (IN_VITRO)"E. coli strains cannot utilize sucrose effectively and dominantly depend on other metabolites from S. elongatus"
E. coli growth on cyanobacterial photosynthate
E. coli W delta-cscR grew on cyanobacterial photosynthate and maintained viability in continuous coculture for more than two weeks. Early batch growth was not primarily attributable to sucrose export; improved sucrose utilization contributed to later PHB production in separately functionalized strains. No product-removal feedback mechanism establishing syntrophy is shown by carbon feeding alone.
Participating Taxa: Escherichia coli W delta-cscR
Metabolites: sucrose (CHEBI:17992 · MediaIngredientMech · CMMMech)
Biological Processes:
- sucrose catabolic process (GO:0005987 · PathwayMech)
HYPOTHESIZED/PARTIAL: photosynthate-supported heterotroph activity could contribute to the observed cyanobacterial growth benefit through metabolite return or byproduct absorption. The study does not isolate sucrose uptake as its cause or identify a necessary exchanged compound; positive and negative effects depend on culture context.
Evidence
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PMID:28127397 - SUPPORT (IN_VITRO)"we determined that co-cultures maintain stable ratios for more than two weeks"
E. coli Stimulation of Cyanobacterial Growth
MUTUALISMThe tested heterotrophic partner increased cyanobacterial abundance relative to axenic controls in low-density cocultures. Together with photosynthate-supported heterotroph growth, this supports conditional reciprocal benefit. It is not universal stability: dense illuminated cyanobacteria could inhibit heterotroph viability. The source proposes metabolite return or byproduct absorption as possible explanations for stimulation, without resolving the mediator; respiratory CO2 alone was considered questionable.
Source Taxon: Escherichia coli W delta-cscR
Target Taxon: Synechococcus elongatus PCC 7942 cscB+
Biological Processes:
- growth (GO:0040007 · PathwayMech)
Evidence
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PMID:28127397 - SUPPORT (IN_VITRO)"inoculation of each heterotrophic species enhanced cyanobacterial growth"
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PMID:28127397 - SUPPORT (IN_VITRO)"all three evolutionarily unrelated heterotrophs can significantly increase cyanobacterial growth under a range of growth conditions "
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which strain- and condition-specific interactions explain growth and persistence in this dyad?
The source combines batch, continuous, density-dependent and production assays. Keep their positive results without treating every partner or strain as persistent for weeks to months. Cyanobacterial growth stimulation is observed, but metabolite return and byproduct absorption remain hypotheses. Light-associated inhibition is supported without identifying oxygen as the exclusive cause. For Bacillus, the canonical168 production assay is distinct from 3610 perturbation experiments. For E. coli, the early non-sucrose inference differs from later sucrose-sensitive production; for yeast, W303Clump is not parental W303. No new causal node, direction, cultivation protocol or strain optimization is added.
Attaches to: ecological_interactions#Photosynthetic carbon supply to E. coli, ecological_interactions#E. coli growth on cyanobacterial photosynthate, ecological_interactions#E. coli Stimulation of Cyanobacterial Growth
1 evidence item(s)
we hypothesize that these benefits arise from emergent cross-feeding of metabolite(s) and/or absorption of byproducts
Source-explicit proposed mediator of cyanobacterial stimulation, not a measured transfer mechanism.
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Light | Continuous illumination | N/A |
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| NaCl (Osmotic Pressure) | Required for sucrose secretion | mM (concentration not specified in abstract) |
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| IPTG (Isopropyl β-D-1-thiogalactopyranoside) | Inducer concentration not specified | N/A |
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Growth Media
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