A defined two-member co-culture of the vaginal commensal Bifidobacterium breve with the sexually transmitted protozoan parasite Trichomonas vaginalis, assayed against HeLa epithelial cells. The result runs counter to the expectation that a beneficial commensal antagonises the parasite: over 4 h the protozoan proliferated 1.2-fold more while bacterial abundance fell 27%, microscopy showed direct physical association between the two organisms, and transcriptomics of T. vaginalis showed upregulation of fatty acid metabolism and DNA replication genes together with virulence-associated genes including adhesins, corroborated by metabolomic changes in long-chain fatty acids. B. breve conferred no protection on host epithelial cells, and the effects on the parasite were transient. The record captures a commensal-parasite association in which the commensal is depleted while the parasite is enhanced.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
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| Bifidobacterium breve | NCBITaxon:1685 · TaxonMech · TraitMech | N/A | |
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| Trichomonas vaginalis | NCBITaxon:5722 · TaxonMech · TraitMech | N/A | |
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| HeLa human epithelial cells — ontology label: Homo sapiens | NCBITaxon:9606 · TaxonMech · TraitMech | N/A | |
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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.
Direct Bifidobacterium-Trichomonas Surface Association
Confocal imaging after 4 hours of anaerobic coculture showed B. breve around the T. vaginalis surface. This supports physical association, not bacterial internalization or contact-dependent mediation of the parallel growth, transcript, lipid and host-assay responses.
Participating Taxa: Bifidobacterium breve, Trichomonas vaginalis
Biological Processes:
- cell adhesion (GO:0007155 · PathwayMech)
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"Microscopy showed a direct physical association between the two organisms"
T. vaginalis Growth with B. breve Attrition
PREDATIONFour-hour coculture increased viable parasite counts by the reported 1.2-fold and reduced bacterial CFUs by 27% relative to controls. PREDATION here follows the local paired benefit/harm (+/-) definition; it does not establish ingestion. The paper explicitly lacked direct evidence of bacterial internalization, and the trophic mechanism remains unresolved.
Participating Taxa: Trichomonas vaginalis, Bifidobacterium breve
Biological Processes:
- cell population proliferation (GO:0008283 · PathwayMech)
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"Co-culture of T. vaginalis with B. breve for 4 h significantly increased protozoan proliferation by 1.2-fold, while bacterial abundance was reduced by 27%"
Parasite DNA-Replication and Energy Response
Parasite RNA-seq after B. breve exposure showed enrichment of DNA-replication, chromatin and ATP synthesis-coupled electron-transport annotations. These are expression responses accompanying higher viable parasite counts, not direct replication-rate, ATP-flux or necessity measurements.
Participating Taxa: Bifidobacterium breve, Trichomonas vaginalis
Biological Processes:
- DNA replication (GO:0006260 · PathwayMech)
PARTIAL - the source proposes that the replication-associated program supports parasite proliferation. Enrichment and viable counts are consistent with this explanation but do not selectively establish pathway mediation of either parasite growth or bacterial CFU loss.
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"Upregulated genes were enriched in pathways related to DNA replication and chromatin organization "
Parasite Fatty-Acid Pathway Response
GSVA identified fatty-acid-biosynthesis and propionate-metabolism pathway annotations in the parasite transcriptional response. This does not demonstrate de-novo fatty-acid synthesis, which the paper notes the parasite lacks, or measure SCFA concentrations or metabolic rates.
Participating Taxa: Bifidobacterium breve, Trichomonas vaginalis
Biological Processes:
- fatty acid metabolic process (GO:0006631 · PathwayMech)
PARTIAL - the source proposes that altered fatty-acid handling contributes to the energetic or biosynthetic demands of parasite growth. Transcript pathway scores are not a selective metabolic perturbation, and the mechanism of bacterial CFU loss remains separate.
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"gene set variation analysis (GSVA) showed increased activity in fatty acid biosynthesis and propionate metabolism pathways "
Fatty-Acid Pool Decrease
Protein-normalized LC-MS in parasite-enriched low-speed pellets detected decreases in 15 fatty-acid pools after four-hour coculture, among 38 identified species containing at least 12 carbons. PARTIAL - increased utilization is the authors' interpretation, not measured uptake, oxidation, turnover or bacterial-to-parasite transfer; sample enrichment does not establish complete lipid-source purity.
Participating Taxa: Bifidobacterium breve, Trichomonas vaginalis
Metabolites: fatty acid (CHEBI:35366 · MediaIngredientMech · CMMMech)
Biological Processes:
- fatty acid metabolic process (GO:0006631 · PathwayMech)
PARTIAL - increased fatty-acid utilization could support parasite biosynthesis and growth in the source's model. Decreased standing pools do not determine turnover or energetic flux and do not explain bacterial CFU loss by themselves.
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"levels of several fatty acids were significantly reduced in the B. breve–treated group relative to the control, including 8 UFAs and 7 SFAs "
Adhesin Transcripts and HeLa Nonprotection
B. breve exposure increased parasite adhesin-associated transcripts, while HeLa assays did not show reduced parasite adherence or epithelial damage. Host pretreatment, simultaneous exposure and exposure to pretreated parasites are distinct designs. Cytokine responses varied by assay and time; lack of cytoprotection is not absence of cytokine effects or proof that adhesins mediate nonprotection.
Participating Taxa: Bifidobacterium breve, Trichomonas vaginalis, HeLa human epithelial cells
Biological Processes:
- cell adhesion (GO:0007155 · PathwayMech)
- inflammatory response (GO:0006954 · PathwayMech)
Evidence
-
PMID:41688526 - SUPPORT (IN_VITRO)"B. breve did not prevent epithelial damage or reduce T. vaginalis adherence"
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PMID:41688526 - SUPPORT (IN_VITRO)"there was an increase in virulence-associated genes, including adhesins"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which contact, lipid and adhesin mechanisms cause the transient coculture and host responses?
The source explicitly lacks direct internalization evidence and proposes future contact-versus-conditioned-medium tests. RNA enrichment and lipid pools do not measure donor transfer, oxidation or necessary growth mediation. Separate HeLa designs show differing cytokine responses; adhesin necessity is not resolved by co-occurrence. Figures, supplementary files and raw ArrayExpress measurements were not inspected.
Attaches to: ecological_interactions#Direct Bifidobacterium-Trichomonas Surface Association, ecological_interactions#T. vaginalis Growth with B. breve Attrition, ecological_interactions#Parasite DNA-Replication and Energy Response, ecological_interactions#Parasite Fatty-Acid Pathway Response, ecological_interactions#Fatty-Acid Pool Decrease, ecological_interactions#Adhesin Transcripts and HeLa Nonprotection
Environmental Factors
| Factor | Value | Unit |
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| Co-culture duration | 4 h | N/A |
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Growth Media
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