A 150-member bacterial synthetic community assembled from genome-sequenced isolates recovered from surface-sterilized Brassicaceae roots, nearly all Arabidopsis thaliana, and applied to Arabidopsis Col-0 plants in gamma-irradiated coconut-coir and MS-agar microcosms. The study used top-down dropout and add-in deconstruction to test SynCom subsets against the leaf pathogen Pseudomonas syringae pv. tomato DC3000, resolving Bacillus and Pseudomonadota as protective components; follow-up halo assays, Bacillus-only inocula, leaf-recovery CFU assays, and Arabidopsis RNA-seq supported a model in which diverse rhizospheric Bacillus suppress Pto without requiring host immune activation.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| 150-member Brassicaceae-root bacterial SynCom — ontology label: Bacteria | NCBITaxon:2 · TaxonMech · TraitMech | N/A | |
|
|||
| protective Bacillus subset — ontology label: Bacillus <firmicutes> | NCBITaxon:1386 · TaxonMech · TraitMech |
PATHOGEN_ANTAGONIST
|
N/A |
|
|||
| protective Pseudomonadota subset — ontology label: Pseudomonadota | NCBITaxon:1224 · TaxonMech · TraitMech |
PATHOGEN_ANTAGONIST
|
N/A |
|
|||
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.
SynCom Colonization and Partial Growth Rescue in Irradiated Coir
The 150-member inoculum established aggregate bacterial communities in Arabidopsis rhizosphere, roots and shoots and partially restored plant growth in irradiated coir. Amplicon reads originated from the inoculum, but individual establishment of every strain was not resolved.
Participating Taxa: 150-member Brassicaceae-root bacterial SynCom
Biological Processes:
- plant-bacterium symbiotic process (GO:0044403 · PathwayMech)
Evidence
-
PMID:40590505 - SUPPORT (IN_VIVO)"We replaced the destroyed microbiota with a 150-member SynCom composed of bacterial isolates previously retrieved from Arabidopsis roots"
-
PMID:40590505 - SUPPORT (IN_VIVO)"We found that 100% of the 16S rRNA gene reads in our data originated from the inoculum"
Bacillus-Dependent Pto Leaf-Pathogen Suppression
Bacillus-only add-ins protected Arabidopsis leaves against Pto, while Bacillus removal impaired protection. Paenibacillus tests did not show the same requirement. These interventions support a protective inoculum effect, not a resolved resource-competition mechanism or causation of the separate follow-up assays.
Participating Taxa: protective Bacillus subset
Biological Processes:
- defense response to bacterium (GO:0042742 · PathwayMech)
Evidence
-
PMID:40590505 - SUPPORT (IN_VIVO)"This process of community deconstruction revealed a critical role for the genus Bacillus in protecting the plant from infection."
-
PMID:40590505 - SUPPORT (IN_VIVO)"Only when multiple Bacillus strains were present together were the leaves protected from infection."
Diverse Bacillus In Vitro Pto Antagonism
Each Bacillus isolate in the screened set inhibited luminescent Pto on LB agar, producing an inhibition halo consistent with secreted diffusible antagonists; antiSMASH did not identify one BGC shared by all Bacillus strains and absent from the rest of the SynCom.
Participating Taxa: protective Bacillus subset
Biological Processes:
- defense response to bacterium (GO:0042742 · PathwayMech)
Evidence
-
PMID:40590505 - SUPPORT (IN_VITRO)"To scan the SynCom members for inhibition of the pathogenic bacterium Pto, we co-cultured each one of the SynCom bacteria with a Pto lawn on agar plates."
-
PMID:40590505 - SUPPORT (IN_VITRO)"As the Bacillus strains all inhibited Pto in vitro and produced an inhibition halo indicative of a diffusible compound"
-
PMID:40590505 - SUPPORT (COMPUTATIONAL)"we could not identify any BGCs that were common to all Bacillus strains and absent in the other strains in the collection"
Pseudomonadota Multi-Class Pto Protection
Pseudomonadota combinations contributed to Pto suppression, but class-level dropouts did not identify a single necessary class. Niche overlap is a proposed explanation; the experiments do not isolate resource competition from other mechanisms.
Participating Taxa: protective Pseudomonadota subset
Biological Processes:
- defense response to bacterium (GO:0042742 · PathwayMech)
Evidence
-
PMID:40590505 - SUPPORT (IN_VIVO)"we separately dropped out each of the three classes Alpha-, Beta-, and Gamma-proteobacteria. None of these drop-outs compromised the protection provided by the SynCom"
-
PMID:40590505 - SUPPORT (IN_VIVO)"in the case of Pseudomonadota, we could not identify a focal taxon"
Bacillus Protection in bbc1 Immune-Impaired Arabidopsis
Bacillus inoculation protected wild-type and bak1/bkk1/cerk1 (bbc1) plants against Pto in the tested open-coir system. This shows protection despite the specified co-receptor defect, not absence of every immune contribution or reciprocal microbial fitness benefit.
Participating Taxa: protective Bacillus subset
Biological Processes:
- defense response to bacterium (GO:0042742 · PathwayMech)
Evidence
-
PMID:40590505 - SUPPORT (IN_VIVO)"Bacillus-inoculated plants from both genotypes were infection free"
-
PMID:40590505 - SUPPORT (IN_VIVO)"We concluded that inoculating the rhizosphere with a consortium of Bacillus strains compensates for the lack of a fully functional immune system, protecting the plant from a leaf pathogen."
Knowledge gaps & discussions (3)
KNOWLEDGE_GAP OPEN How much of the Bacillus-mediated leaf protection comes from direct leaf-level antagonism versus induced systemic resistance from the root compartment?
Bacillus strains could be recovered from leaves and protected immune-impaired bbc1 plants, but the study leaves induced-resistance contributions unresolved.
Attaches to: ecological_interactions#Bacillus-Dependent Pto Leaf-Pathogen Suppression, ecological_interactions#Bacillus Protection in bbc1 Immune-Impaired Arabidopsis
1 evidence item(s)
further research into the involvement of induced resistance is needed in order to fully tease apart induced immunity from direct pathogen inhibition
Records the authors' stated uncertainty about the relative contribution of direct Bacillus-Pto antagonism and systemic host immunity.
KNOWLEDGE_GAP OPEN Which Pseudomonadota class or lower-resolution taxon combinations are sufficient to suppress Pto in this SynCom?
The first-round screen implicated the Pseudomonadota phylum, but second-round class add-ins and dropouts did not resolve a single focal class or genus.
Attaches to: ecological_interactions#Pseudomonadota Multi-Class Pto Protection
1 evidence item(s)
In contrast to Bacillus, in the case of Pseudomonadota, we could not identify a focal taxon
Supports an explicit gap rather than inventing a Pseudomonadota class-level driver.
KNOWLEDGE_GAP OPEN Which inhibitory mechanisms account for protection, and what fitness effects do the protective bacteria experience?
PMID:40590505 directly supports add-in/dropout protection and in-vitro inhibition. Halo assays suggest diffusible antagonism, while Pseudomonadota niche competition remains hypothetical. The bbc1 test does not remove all host immune pathways. Existing direct-versus-systemic and focal-taxon gaps remain; source-to-follow-up-experiment relations are not ecological arrows.
Attaches to: ecological_interactions#SynCom Colonization and Partial Growth Rescue in Irradiated Coir, ecological_interactions#Bacillus-Dependent Pto Leaf-Pathogen Suppression, ecological_interactions#Diverse Bacillus In Vitro Pto Antagonism, ecological_interactions#Pseudomonadota Multi-Class Pto Protection, ecological_interactions#Bacillus Protection in bbc1 Immune-Impaired Arabidopsis
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
NCBI BioProject PRJNA1175571
NCBI BioProject holding the 16S rRNA gene amplicon sequencing data from the SynCom compartments. |
OTHER | PRJNA1175571 |
|
||
|
GEO transcriptomic series GSE285599
Gene Expression Omnibus series for raw Arabidopsis RNA-seq data from SynCom and Pto treatments. |
OTHER | GSE285599 |
|
||
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| closed gamma-irradiated coir microcosm | three 25 kGy gamma-irradiation rounds, 30 ml sterile liquid MS medium, 5 ml bacterial suspension | N/A |
|
||
| Pto-lux leaf challenge endpoint | 6 days post-infection | N/A |
|
||
Growth Media
Cross-Mech Suite Links
Explore related entities across the CultureBotAI X-Mech knowledge bases: