Mesorhizobium TaiHu-Synechococcus PCC 7002 Vitamin B12 Synthetic Consortium

Community ID CommunityMech:000315

Ecological State ENGINEERED

Environment laboratory co-culture
ENVO:01001405

Modeled Environment Lake Taihu freshwater bloom
ENVO:00000021

A synthetic consortium built by co-culturing the marine cyanobacterium Synechococcus sp. PCC 7002 (Syn7002) — a model strain that lacks the gene cluster for vitamin B12 biosynthesis and therefore depends on other microbes for it — with a bloom-forming Microcystis community from Lake Taihu, then purifying the result. Metagenomics showed the early community consisted mainly of Syn7002, Mesorhizobium sp. TaiHu (MesTH) and Pseudomonas sp. TaiHu (PseTH); PseTH declined once the community stabilised, leaving the cyanobacterium and MesTH as the persistent pair. Electron microscopy found rod-shaped bacteria clustered around Syn7002 cells. Metatranscriptomics showed vitamin B12 biosynthesis and transport genes significantly upregulated in MesTH, and B12-positive control experiments supported complementarity between the two strains, so the community is a worked example of a vitamin auxotrophy being satisfied by a partner rather than by the medium.

Taxonomy

Taxon	Ontology ID	Functional Roles	Abundance
Synechococcus sp. PCC 7002 (Syn7002)	NCBITaxon:32049	PRIMARY_PRODUCER	N/A
PMID:41790499 - SUPPORT (IN_VITRO) "The marine cyanobacterium Synechococcus sp. PCC 7002 (Syn7002) is a model organism that lacks the gene cluster required for vitamin B12 biosynthesis, necessitating cooperative interactions with other microbes"
Mesorhizobium sp. TaiHu (MesTH)	NCBITaxon:68287	CROSS_FEEDER	N/A
PMID:41790499 - SUPPORT (IN_VITRO) "Transcriptomic data further indicated that vitamin B12 biosynthesis and transport genes were significantly upregulated in MesTH"
Pseudomonas sp. TaiHu (PseTH)	NCBITaxon:286		N/A
PMID:41790499 - SUPPORT (IN_VITRO) "the early-stage community consisted mainly of Syn7002, Mesorhizobium sp. TaiHu (MesTH) and Pseudomonas sp. TaiHu (PseTH), although the abundance of PseTH declined after community stabilization"
bloom-forming Microcystis community (source inoculum)	NCBITaxon:1125		N/A
PMID:41790499 - PARTIAL (IN_VITRO) "co-culturing Syn7002 with a bloom-forming Microcystis community"

Ecological Interactions

Taxon

Cross-feeding

Colonization facilitation

Vitamin B12 Provision from Mesorhizobium TaiHu to Synechococcus PCC 7002

CROSS_FEEDING

Source Taxon: Mesorhizobium sp. TaiHu (MesTH)

Target Taxon: Synechococcus sp. PCC 7002 (Syn7002)

Metabolites: vitamin B12 (CHEBI:176843)

Evidence

PMID:41790499 - PARTIAL (IN_VITRO)

"The results further suggest that MesTH promotes the growth of Syn7002 in the community by providing the small amount of vitamin B12 needed for its growth"

Close Spatial Association of Partner Bacteria with Syn7002 Cells

COLONIZATION_FACILITATION

Evidence

PMID:41790499 - PARTIAL (IN_VITRO)

"Electron microscopy revealed numerous rod-shaped bacteria clustered around Syn7002 cells, indicating close spatial associations between species"

Environmental Factors

Factor	Value	Unit
Vitamin B12-positive control supplementation		N/A
PMID:41790499 - SUPPORT (IN_VITRO) "Combined with vitamin B12-positive control experiments, these results confirm potential vitamin B12 complementarity between the two strains"

Growth Media

Vitamin B12-supplemented BG11, Syn7002 culture

Temperature 28.0 CELSIUS

Composition

Component	Concentration	Unit	CHEBI
BG11	N/A	N/A	N/A
vitamin B12	4.0	µg/L	N/A

Preparation notes: The cyanobacterial partner's culture, and the axis the record is about - the B12-free form of the same medium is what makes MesTH's provision measurable. The 4 µg/L figure is the supplement used for the Syn7002+B12 control arm. Extracted from the cached open-access full text; #183 listed this record as lacking growth conditions because they are Methods-level.

Evidence

PMID:41790499

"was cultivated in vitamin B12-supplemented BG11 medium at 28 °C under a light intensity of 70 µmol m−2 s−1 with shaking at 180 r.p.m."

PMID:41790499

"For the Syn7002+vitamin B12 group, vitamin B12 (4 µg l−1) was supplemented"

LB, MesTH isolation and culture

Temperature 28.0 CELSIUS

Composition

Component	Concentration	Unit	CHEBI
LB	N/A	N/A	N/A

Preparation notes: The bacterial partner was purified and grown on LB, then washed into B12-free BG11 before the co-culture, so the only B12 in the assay is what MesTH makes.

Evidence

PMID:41790499

"MesTH was purified using the streak plate method on LB medium, after which it was cultured in LB medium. Both MesTH and Syn7002 were then washed with vitamin B12-free BG11"