Suillus clintonianus-Bacillus altitudinis Thiamine Cross-Feeding SynCom

Community ID CommunityMech:000312

Ecological State ENGINEERED

Environment pine mycorrhizosphere
ENVO:00005801

Modeled Environment pine rhizosphere
ENVO:00005801

A cross-domain synthetic community in which the ectomycorrhizal fungus Suillus clintonianus, which cannot effectively obtain or synthesize the thiamine (vitamin B1) it needs for growth, recruits the hyphae-associated bacterium Bacillus altitudinis B4 to its mycelial surface. The fungus first secretes ureidosuccinic acid and pregnenolone to recruit the bacterium; the secreted ureidosuccinic acid then stimulates B. altitudinis B4 to increase biomass and upregulate thiamine biosynthesis genes, enhancing thiamine production. The fungus absorbs the bacterially produced thiamine, which promotes fungal growth and increases the ectomycorrhizal colonization rate of the host pine Pinus massoniana. The mechanism, resolved by nontargeted metabolomics and whole-genome sequencing, illustrates a vitamin-mediated tripartite symbiosis in which a prototrophic bacterial partner fulfills a fungal thiamine auxotrophy to support host-fungal mutualism.

Taxonomy

Taxon	Ontology ID	Functional Roles	Abundance
Suillus clintonianus	NCBITaxon:1904413	CROSS_FEEDER	DOMINANT
PMID:41454778 - SUPPORT (IN_VITRO) "ectomycorrhizal fungus Suillus clintonianus" PMID:41454778 - SUPPORT (IN_VITRO) "some ectomycorrhizal fungi cannot effectively obtain the thiamine necessary for growth from their host or synthesize it themselves"
Bacillus altitudinis B4	NCBITaxon:293387	CROSS_FEEDER	DOMINANT
PMID:41454778 - SUPPORT (IN_VITRO) "hyphae-associated bacterium Bacillus altitudinis B4" PMID:41454778 - SUPPORT (IN_VITRO) "enhance thiamine production by increasing its biomass and upregulating the expression of related functional genes"
Pinus massoniana	NCBITaxon:88730		DOMINANT
PMID:41454778 - SUPPORT (IN_VIVO) "increasing the colonization rate in association with Pinus massoniana"

Ecological Interactions

Taxon

Cross-feeding

Mutualism

Colonization facilitation

Fungal recruitment of the hyphae-associated bacterium

COLONIZATION_FACILITATION

Source Taxon: Suillus clintonianus

Target Taxon: Bacillus altitudinis B4

Metabolites: ureidosuccinic acid (CHEBI:15859), pregnenolone (CHEBI:16581)

Evidence

PMID:41454778 - SUPPORT (IN_VITRO)

"S. clintonianus first secreted ureidosuccinic acid and pregnenolone, recruiting the hyphae-associated bacterium B. altitudinis B4 to the mycelial surface"

Ureidosuccinic acid stimulation of bacterial thiamine production

CROSS_FEEDING

Source Taxon: Suillus clintonianus

Target Taxon: Bacillus altitudinis B4

Metabolites: ureidosuccinic acid (CHEBI:15859)

Biological Processes:

thiamine biosynthetic process (GO:0009228)

Evidence

PMID:41454778 - SUPPORT (IN_VITRO)

"the ureidosuccinic acid secreted by S. clintonianus further stimulated B. altitudinis B4 to enhance thiamine production"

Thiamine provisioning fulfilling the fungal requirement

CROSS_FEEDING

Source Taxon: Bacillus altitudinis B4

Target Taxon: Suillus clintonianus

Metabolites: thiamine (CHEBI:18385)

Biological Processes:

thiamine biosynthetic process (GO:0009228)

Evidence

PMID:41454778 - SUPPORT (IN_VITRO)

"S. clintonianus absorbed the thiamine secreted by the B. altitudinis B4, promoting fungal growth"

Enhanced ectomycorrhizal colonization of the pine host

MUTUALISM

Source Taxon: Suillus clintonianus

Target Taxon: Pinus massoniana

Evidence

PMID:41454778 - SUPPORT (IN_VIVO)

"promoting fungal growth and increasing the colonization rate in association with Pinus massoniana"

External Resources

Name	Repository	Resource ID
Primary publication - thiamine cross-feeding in an ectomycorrhizal SynCom Primary study establishing that Suillus clintonianus recruits Bacillus altitudinis B4 to metabolize thiamine and promote Pinus massoniana symbiosis, using nontargeted metabolomics and whole-genome sequencing.	OTHER	PMID:41454778
PMID:41454778 - SUPPORT (IN_VITRO) "Ectomycorrhizal fungi recruit hyphae-associated bacteria that metabolize thiamine to promote pine symbiosis"

Environmental Factors

Factor	Value	Unit
Thiamine limitation of the fungal partner	fungus cannot effectively obtain or synthesize thiamine	N/A
PMID:41454778 - SUPPORT (IN_VITRO) "some ectomycorrhizal fungi cannot effectively obtain the thiamine necessary for growth from their host or synthesize it themselves"

Growth Media

Potato dextrose agar, ectomycorrhizal fungal isolation and culture

pH 7.0

Temperature 28.0 CELSIUS

Composition

Component	Concentration	Unit	CHEBI
potato extract	200.0	g/L	N/A
glucose	20.0	g/L	N/A
agar	15.0	g/L	N/A
streptomycin	50.0	mg/L	N/A

Preparation notes: The fungal partner's medium. Streptomycin is in the recipe to suppress bacteria during isolation from sporocarp tissue, so it belongs to the isolation step rather than to the co-culture. Extracted from the cached open-access full text - this record was among the 42 that #183 treated as access-blocked until the full-text sweep reached them.

Evidence

PMID:41454778

"potato dextrose agar medium (PDA, 200 g L−1 potato extract, 20 g L−1 glucose, and 15 g L−1 agar, 50 mg L−1 streptomycin, pH 7.0) at 28°C"

LB, bacterial partner culture

pH 7.0

Temperature 37.0 CELSIUS

Composition

Component	Concentration	Unit	CHEBI
tryptone	10.0	g/L	N/A
yeast extract	5.0	g/L	N/A
sodium chloride	10.0	g/L	N/A

Preparation notes: The bacterial partner, grown separately at a different temperature from the fungus - 37C against the fungus's 28C - and washed into 0.9% NaCl before the inoculum density was set by OD600.

Evidence

PMID:41454778

"LB medium (tryptone 10 g L−1, yeast extract 5 g L−1, and NaCl 10 g L−1, pH 7.0) at 37°C"

PMID:41454778

"Bacteria were grown and maintained in 50 ml LB medium at 37°C for 12 h"

Confrontation assay plate

Temperature 28.0 CELSIUS

Preparation notes: The interaction assay itself, read as mycelial area after 14 days.

Evidence

PMID:41454778

"Fungal plugs (8 mm) were placed in the center of the plate (60 mm) and incubated at 28°C in the dark"