A defined 16-member marine algal-bacterial holobiont in which Prymnesium parvum CCAP 646/6 was cocultured in L1 medium with a 15-strain synthetic bacterial community and monitored under nitrogen, phosphorus, or vitamin B12 limitation. Patron et al. (2026) inoculated all SynCom bacteria in equal proportions and compared photobioreactor cultures with and without the SynCom for 14 days. Nitrogen and phosphorus limitation did not reveal a major growth benefit from the SynCom, whereas B12 limitation triggered a mutualistic state in which bacterial cobalamin provisioning rescued algal growth, B12-producing bacteria upregulated cobalamin biosynthesis, and B12-auxotrophic bacteria induced vitamin transport and B12-dependent enzymes. +
+Taxonomy
+| Taxon | +Ontology ID | +Functional Roles | +Abundance | +
|---|---|---|---|
| + Prymnesium parvum CCAP 646/6 + | ++ + NCBITaxon:97485 + + | +
+
+
+
+ PRIMARY_PRODUCER
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Cyclobacterium sp. 09-022 + | ++ + NCBITaxon:68288 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Maribacter sp. 09-009 + | ++ + NCBITaxon:252356 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Muricauda sp. 10-244 + | ++ + NCBITaxon:111500 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Marinovum algicola 19-037 + | ++ + NCBITaxon:42444 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Marivita cryptomonadis 10-255 + | ++ + NCBITaxon:505252 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Roseobacter sp. 09-029 + | ++ + NCBITaxon:2433 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Thalassospira sp. 19-025 + | ++ + NCBITaxon:168934 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Alteromonas sp. 002 19-002 + | ++ + NCBITaxon:226 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Alteromonas sp. 005 19-005 + | ++ + NCBITaxon:226 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Halomonas alkaliphila 09-027 + | ++ + NCBITaxon:272774 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Halomonas sp. 19-001 + | ++ + NCBITaxon:2745 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Marinobacter sp. 10-113 + | ++ + NCBITaxon:2742 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Vibrio aestuarianus 23-001 + | ++ + NCBITaxon:28171 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Vibrio diazotrophicus 23-002 + | ++ + NCBITaxon:685 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
| + Pseudomonas stutzeri 23-003 + | ++ + NCBITaxon:316 + + | +
+
+
+
+ CROSS_FEEDER
+
+
+
+ |
+ COMMON | +
+
|
+ |||
Ecological Interactions
+ + + +B12-limited holobiont mutualism
+ MUTUALISM +Metabolites: + + vitamin B12 + (CHEBI:176843) + +
+ + + +Biological Processes:
+-
+
+
- + biological process involved in interspecies interaction between organisms + (GO:0044419) + + +
Evidence
+-
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"B12-limitation triggered a strong mutualistic interaction in which the SynCom enabled a three-fold increase in algal biomass +"+ +
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"bacterial B12 production alleviated the limitation +"+ +
+
+
Cobalamin biosynthesis by B12-producing SynCom members
+ CROSS_FEEDING +Metabolites: + + cobalamin + (CHEBI:30411) + +
+ + + +Biological Processes:
+-
+
+
- + cobalamin biosynthetic process + (GO:0009236) + + +
Evidence
+-
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"B12-producers (Marinovum algicola, Roseobacter sp., Halomonas sp.) upregulated cobalamin biosynthesis exclusively under B12-limitation +"+ +
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"Enrichment of B12-producing taxa (i.e. Marinovum algicola, Roseobacter sp., Halomonas sp.) under B12-lim coincided with the upregulation of cobalamin biosynthesis pathways +"+ +
+
+
Auxotrophic SynCom B12 acquisition
+ COMPETITION +Metabolites: + + cobalamin + (CHEBI:30411) + +
+ + + +Biological Processes:
+-
+
+
- + biological process involved in interspecies interaction between organisms + (GO:0044419) + + +
Evidence
+-
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"several B12-auxotrophic taxa induced B12-transport and B12-requiring enzymes, indicating active vitamin exchange within the holobiont +"+ +
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"non-B12 producers Cyclobacterium qasimii, Marivita cryptomonadis, Marinobacter sp., and Pseudomonas stutzeri, which also upregulated B12-dependent genes, strongly induced most of their B12 transporters under B12-lim conditions +"+ +
+
+
Algal organic-matter support of heterotrophic bacteria
+ MUTUALISM +Biological Processes:
+-
+
+
- + photosynthesis + (GO:0015979) + + +
- + biological process involved in interspecies interaction between organisms + (GO:0044419) + + +
Evidence
+-
+
+
-
+ + + PMID:42549325 + + - SUPPORT (IN_VITRO) ++ +"Heterotrophic bacteria dependent on algal organic matter synthesize and mobilize B12 under nutrient stress, and both partners utilize it. +"+ +
+
+
Associated Datasets
+| Dataset | +Type | +Repository | +Accession | +
|---|---|---|---|
|
+ P. parvum SynCom metabarcoding, RNA-seq, and bacterial genome sequencing
+
+ European Nucleotide Archive project containing metabarcoding, RNA-seq, and bacterial genome sequencing data for the nutrient-limited P. parvum SynCom. + + + |
+ MULTI_OMICS | +ENA | ++ + PRJEB106332 + + | +
|
+ P. parvum SynCom metabolomics and prymnesin mass-spectrometry data
+
+ Full-scan and MS/MS metabolomics data for intracellular and extracellular extracts from the nutrient-limited P. parvum SynCom experiment. + + + |
+ METABOLOMICS | +OTHER | ++ + + + | +
|
+ Prymnesium parvum genome assembly used for RNA-seq mapping
+
+ P. parvum genome assembly used for host transcriptome mapping. + + |
+ GENOMICS | +OTHER | ++ + + + | +
Knowledge gaps & discussions (1)
+ ++ KNOWLEDGE_GAP + OPEN + Does P. parvum acquire bacterial B12 primarily from passive extracellular release, bacterial lysis, prophage- or phage-mediated release, or bacterivory of the SynCom partners? + +
+The source supports bacterial B12 production and auxotrophic acquisition but explicitly leaves the cellular route of vitamin release and transfer unresolved. +
+ +Attaches to: ecological_interactions#B12-limited holobiont mutualism, ecological_interactions#Cobalamin biosynthesis by B12-producing SynCom members
1 proposed experiment(s)
+ +Approach: defined-coculture growth assay with targeted bacterial genetics +
Decision: Loss of algal rescue in a specific mutant background, restored by exogenous B12, would prioritize that release route. + +
1 evidence item(s)
+ +The precise mechanism of B12 transfer remains unresolved. Not only are the potential acquisition routes unclear, but the identity of bacterial exporters mediating vitamin release is also unknown. +
+States the open mechanistic question around B12 export and acquisition. +
+Environmental Factors
+| Factor | +Value | +Unit | +
|---|---|---|
| vitamin B12 limitation | +7.4 x 10^-6 uM vitamin B12 | +N/A | +
+
|
+ ||
| nitrogen limitation | +62 uM N | +N/A | +
+
|
+ ||
| phosphorus limitation | +2.2 uM P | +N/A | +
+
|
+ ||
| oxic continuous-light phenotyping | +100 umol photons m-2 s-1 at pH 8.2 and 20 C | +N/A | +
+
|
+ ||