A synthetic, light-driven consortium pairing the cyanobacterium Synechococcus elongatus PCC 7942 (engineered to secrete sucrose via the cscB+ transporter) with the budding yeast Saccharomyces cerevisiae W303Clump. The cyanobacterium fixes CO2 and exports sucrose, which supports heterotrophic growth of the yeast. Wild-type W303 did not grow in co-culture; W303Clump, an evolved derivative carrying mutations that enhance fitness in dilute sucrose, did, and maintained viability in continuous co-culture for more than two 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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DOMINANT |
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| Saccharomyces cerevisiae W303Clump — ontology label: Saccharomyces cerevisiae | NCBITaxon:4932 · TaxonMech · TraitMech |
CROSS_FEEDER
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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.
CO2 Fixation and Sucrose Production
CROSS_FEEDINGCscB+ S. elongatus fixes carbon and exports sucrose that supports the evolved S. cerevisiae W303Clump partner. The parental W303 did not grow in the tested cocultures; the positive carbon-supply result is specific to W303Clump and the tested conditions.
Source Taxon: Synechococcus elongatus PCC 7942 cscB+
Target Taxon: Saccharomyces cerevisiae W303Clump
Metabolites: sucrose (CHEBI:17992 · MediaIngredientMech · CMMMech)
Biological Processes:
- photosynthesis (GO:0015979 · PathwayMech)
- sucrose biosynthetic process (GO:0005986 · PathwayMech)
The sucrose exported by engineered S. elongatus is the fixed carbon source that supports the evolved Saccharomyces cerevisiae W303Clump partner in continuous coculture.
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"
Sucrose Utilization by the Heterotrophic Partner
W303Clump utilized cyanobacterial sucrose and persisted for more than two months in continuous coculture. Separate continuous experiments demonstrated persistence during light-dark cycling; the two-month duration is not assigned to that diurnal assay. Initial growth followed by declining viability in batch culture is a distinct result. Parental W303 did not grow in the tested coculture; the study does not demonstrate a bioproduct for this yeast dyad.
Participating Taxa: Saccharomyces cerevisiae W303Clump
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)"S. cerevisiae W303Clump maintains viability in continuous culture with sucrose-secreting S. elongatus for greater than two months"
Yeast 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: Saccharomyces cerevisiae W303Clump
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#CO2 Fixation and Sucrose Production, ecological_interactions#Sucrose Utilization by the Heterotrophic Partner, ecological_interactions#Yeast 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.
Growth Media
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