A three-member Bacillus synthetic microbial community assembled from Bacillus amyloliquefaciens G12, Bacillus pumilus Y4, and Bacillus velezensis X25 to combine complementary antagonistic activities against Fusarium oxysporum and Phytophthora nicotianae, the causal agents of tobacco Fusarium root rot and black shank. G12 was isolated from the tobacco rhizosphere and the Y4 and X25 endophytes from tobacco tissues in Luoyang, China. The strains showed only mild mutual inhibition in pairwise plate confrontations, the 1:1:1 SynCom produced more indole-3-acetic acid than any single strain, and glasshouse and two-site field assays linked the consortium to reduced soil-borne disease, improved tobacco root traits, and higher middle-leaf-based estimated yield.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Bacillus amyloliquefaciens G12 — ontology label: Bacillus amyloliquefaciens | NCBITaxon:1390 · TaxonMech · TraitMech |
PATHOGEN_ANTAGONIST
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DOMINANT |
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| Bacillus pumilus Y4 — ontology label: Bacillus pumilus | NCBITaxon:1408 · TaxonMech · TraitMech |
PATHOGEN_ANTAGONIST
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DOMINANT |
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| Bacillus velezensis X25 — ontology label: Bacillus velezensis | NCBITaxon:492670 · TaxonMech · TraitMech |
PATHOGEN_ANTAGONIST
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DOMINANT |
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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.
Mild-Inhibition Three-Strain SynCom Compatibility
COMPETITIONPairwise plate confrontations among Bacillus amyloliquefaciens G12, Bacillus pumilus Y4, and Bacillus velezensis X25 all stayed in the Type II mild-inhibition class below 25%, consistent with the limited interstrain growth interference used to assemble the tobacco SynCom.
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:42388034 - SUPPORT (IN_VITRO)"Pairwise plate confrontation assays showed that all interactions among the three Bacillus strains exhibited mild inhibition"
SynCom Indole-3-Acetic Acid Enhancement
The equal-volume co-culture had 11.57 +/- 0.24 mg/L IAA by the reported Salkowski assay, higher than the three monocultures. This is a per-volume colorimetric output, not resolved metabolic exchange, reciprocal fitness or demonstrated IAA-mediated plant protection.
Metabolites: indole-3-acetic acid (CHEBI:16411 · MediaIngredientMech · CMMMech)
Biological Processes:
- indole-3-acetic acid biosynthetic process (GO:0009684 · PathwayMech)
Evidence
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PMID:42388034 - SUPPORT (IN_VITRO)"The SynCom produced significantly more IAA than any single strain"
Tobacco FO/PN Glasshouse Disease Suppression
In two 21-day glasshouse experiments on He Luo No. 1 tobacco seedlings, the SynCom reduced Fusarium oxysporum/Phytophthora nicotianae disease severity under both preventive and curative timing, with preventive treatment lowering disease index from 54.07 to 9.26.
Biological Processes:
- defense response (GO:0006952 · PathwayMech)
Evidence
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PMID:42388034 - SUPPORT (IN_VIVO)"Preventive application was more effective, lowering DI by 82.87% compared to the pathogen control"
Tobacco Root Activity Improvement
Under pathogen stress, SynCom-treated tobacco (Nicotiana tabacum) roots showed 20.27-45.38% higher TTC/dehydrogenase-based activity than single-strain preventive treatments. This root metabolic readout is not a direct biomass-growth measurement or evidence of reciprocal microbial benefit.
Evidence
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PMID:42388034 - SUPPORT (IN_VIVO)"SynCom significantly enhanced root activity compared with single‐strain treatments"
Two-Site Field Disease Suppression and Yield Increase
In two yellow-soil tobacco (Nicotiana tabacum) field sites near Luoyang, two SynCom root-irrigation treatments reduced naturally co-occurring Fusarium root rot and black shank while increasing middle-leaf-based estimated yield relative to the single-strain and commercial microbial treatments.
Biological Processes:
- defense response (GO:0006952 · PathwayMech)
- plant growth (GO:0040007 · PathwayMech)
Evidence
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PMID:42388034 - SUPPORT (IN_VIVO)"SynCom achieved 34.7–40.0% disease suppression and 37.5–41.3% yield increases across sites"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which metabolites and colonization dynamics connect Bacillus G12/Y4/X25 co-cultivation to tobacco root signaling, pathogen inhibition, and persistence in tobacco rhizosphere or endophytic niches?
The reviewed cache contains selected methods/results/discussion, not independent complete full text. Plate inhibition, Salkowski output, glasshouse disease/root activity and estimated middle-leaf field yield are distinct endpoints. Hormonal mediation, strain persistence and member-specific fitness remain unresolved. Nonsignificant genus-level amplicon shifts do not establish colonization or pathogen decline. IAA-specific GO:0009684 already satisfies issue #880; the root TTC node's growth annotation is removed separately.
Attaches to: ecological_interactions#Mild-Inhibition Three-Strain SynCom Compatibility, ecological_interactions#SynCom Indole-3-Acetic Acid Enhancement, ecological_interactions#Tobacco FO/PN Glasshouse Disease Suppression, ecological_interactions#Tobacco Root Activity Improvement, ecological_interactions#Two-Site Field Disease Suppression and Yield Increase, engineering_design#assembly_strategy
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication - Bacillus G12-Y4-X25 tobacco SynCom
Pest Management Science 2026 open-access primary article, doi:10.1002/ps.71069, describing the three-member Bacillus SynCom for Fusarium root rot and black shank control in tobacco. |
OTHER | PMID:42388034 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| function-guided three-strain Bacillus design | Bacillus amyloliquefaciens G12 + Bacillus pumilus Y4 + Bacillus velezensis X25 | 1:1:1 LB broth mixture |
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Growth Media
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