A defined two-member marine algae-bacteria co-culture pairing the model diatom Phaeodactylum tricornutum CCAP 1055/1 with the heterotrophic marine bacterium Aliivibrio fischeri MCCC 1H00019. Chen et al. 2026 grew the pair in EASW medium supplemented with 30% marine broth under a 12 h light/12 h dark cycle and used 4-day and 8-day samples to show bacterial surface colonization, competitive rather than growth-promoting behavior, a day-6 extracellular-polymeric-substance peak followed by day-8 depletion, and time-dependent rewiring of P. tricornutum photosynthetic physiology, transcriptomic rhythmicity, and model-inferred biomass flux.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
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| Phaeodactylum tricornutum CCAP 1055/1 — ontology label: Phaeodactylum tricornutum | NCBITaxon:2850 · TaxonMech · TraitMech |
PRIMARY_PRODUCER
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DOMINANT |
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| Aliivibrio fischeri MCCC 1H00019 — ontology label: Aliivibrio fischeri | NCBITaxon:668 · TaxonMech · TraitMech | 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.
Aliivibrio Surface Colonization of Phaeodactylum
SEM showed A. fischeri attached to P. tricornutum surfaces in the 30% marine-broth coculture. Filamentous structures were interpreted as likely EPS from one or both partners; neither their chemical identity nor their producer was established by microscopy. Preserve the physical association without treating it as proof of nutrient transfer or the cause of photosynthetic decline.
Source Taxon: Aliivibrio fischeri MCCC 1H00019
Target Taxon: Phaeodactylum tricornutum CCAP 1055/1
Evidence
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PMID:42668638 - SUPPORT (IN_VITRO)"Scanning electron microscopy (SEM) analysis demonstrated significant colonization of P. tricornutum cell surfaces by A. fischeri"
Proposed Amino Acid Resource Competition
COMPETITIONHYPOTHESIZED - Nutrient and pigment profiles led the authors to propose early amino-acid competition. Nitrate-N and orthophosphate were measured, but amino-acid depletion and partner-resolved exchange were not. Medium-matched axenic HAC controls support a negative coculture effect on late photosynthetic performance; moderate broth enrichment itself supported axenic growth. These observations do not isolate amino-acid competition as the mechanism or show bacterial growth promotion by bioluminescence.
Participating Taxa: Phaeodactylum tricornutum CCAP 1055/1, Aliivibrio fischeri MCCC 1H00019
Evidence
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PMID:42668638 - PARTIAL (IN_VITRO)"These results are more consistent with a competitive effect in co-culture than with a growth-promoting role of A. fischeri."
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PMID:42668638 - PARTIAL (IN_VITRO)"The observed nutrient depletion patterns and pigment dynamics suggest early-phase competition for amino acid resources between P. tricornutum and A. fischeri"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which processes connect bacterial association to diatom physiological and diel responses?
Keep SEM attachment and medium-controlled late physiological decline as positive findings. Matched late physiological controls exist, but no day-8 axenic transcriptome was collected; age, nutrients and growth phase confound attribution of Co8d transcription to bacteria alone. Light-dark rhythmic gene counts do not establish endogenous clock disruption. Biomass-flux changes (+81%/-87%) are transcript-constrained model predictions, not measured intracellular or interspecies flux. EPS decline admits synthesis, dilution and catabolism explanations. Dedicated physiological/diel/model response structure remains issue #1698, with a one-community Edison dry run and no paid report; no new arrow is inferred from the two existing nodes.
Attaches to: ecological_interactions#Aliivibrio Surface Colonization of Phaeodactylum, ecological_interactions#Proposed Amino Acid Resource Competition
2 evidence item(s)
Scanning electron microscopy (SEM) analysis demonstrated significant colonization of P. tricornutum cell surfaces by A. fischeri
Supports bacterial attachment to the diatom cell surface in co-culture.
The observed nutrient depletion patterns and pigment dynamics suggest early-phase competition for amino acid resources between P. tricornutum and A. fischeri
Supports the authors' competition interpretation; nutrient/pigment observations do not directly identify exchanged or limiting amino acids.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary article - Phaeodactylum-Aliivibrio diel co-culture
iScience article reporting how A. fischeri alters P. tricornutum chronobiology and physiology in a defined algae-bacteria co-culture. |
OTHER | doi:10.1016/j.isci.2026.117307 |
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Phaeodactylum-Aliivibrio RNA-seq BioProject PRJNA1280653
NCBI BioProject accession for sequencing data from the co-culture study. |
OTHER | PRJNA1280653 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| EPS depletion during prolonged co-culture | peak at day 6 followed by day-8 reduction | N/A |
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| Rhythmic gene decrease by day 8 | 7,215 rhythmic genes in Co8d versus 8,619 in the axenic control | N/A |
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| Biphasic modeled biomass flux | +81% in Co4d; -87% in Co8d | N/A |
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Growth Media
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