A two-species soil-bacterial model community composed of Pseudomonas fluorescens Pf0-1 and Pedobacter sp. V48. When mixed on low-nutrient, high-salt hard agar, the two sessile monocultures produce an emergent interspecies social spreading phenotype in which both bacteria comigrate across the agar surface. The system is used to study contact-dependent and environment-dependent emergent motility in small soil microbial communities.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Pseudomonas fluorescens Pf0-1 — ontology label: Pseudomonas fluorescens | NCBITaxon:294 · TaxonMech · TraitMech |
CROSS_FEEDER
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N/A |
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| Pedobacter sp. V48 — ontology label: Pedobacter | NCBITaxon:84567 · TaxonMech · TraitMech |
CROSS_FEEDER
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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.
Interspecies Social Spreading
The canonical two-species coculture spreads across hard agar under the tested conditions while neither monoculture shows the same behavior. Preserve this emergent joint phenotype without assigning an untested one-way inducer or a specific motility motor.
Participating Taxa: Pseudomonas fluorescens Pf0-1, Pedobacter sp. V48
Biological Processes:
- locomotion (GO:0040011 · PathwayMech)
- biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)
Emergent social spreading carries both species across the hard-agar surface rather than releasing only one partner from the colony.
Evidence
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PMID:30700513 - SUPPORT (IN_VITRO)"coculture reveals an emergent phenotype that we term “interspecies social spreading,” where the mixed colony spreads across the hard surface"
Pseudomonas-Pedobacter Comigration
Culture recovery and fluorescent imaging detected both partners throughout the spreading colony, with reproducible nonhomogeneous spatial distributions. This supports comigration rather than one partner escaping, not proof of reciprocal fitness benefits or a feedback cause of initiation.
Participating Taxa: Pseudomonas fluorescens Pf0-1, Pedobacter sp. V48
Biological Processes:
- locomotion (GO:0040011 · PathwayMech)
- biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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PMID:30700513 - SUPPORT (IN_VITRO)"Both species remain associated throughout the spreading colony"
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PMID:30700513 - SUPPORT (IN_VITRO)"we recovered both species from each point in the spreading colony"
Contact-Dependent Initiation
Close physical association was required for initiation in the canonical pair: spreading followed colony contact, and semipermeable separation prevented it. PARTIAL: the molecular trigger and whether direct cell-cell signaling or a localized environmental process mediates the requirement remain unresolved.
Participating Taxa: Pseudomonas fluorescens Pf0-1, Pedobacter sp. V48
Biological Processes:
- cell communication (GO:0007154 · PathwayMech)
- biological process involved in interspecies interaction between organisms (GO:0044419 · PathwayMech)
Close association or contact between Pf0-1 and V48 initiates the two-species colony expansion phenotype on hard agar.
Evidence
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PMID:30700513 - SUPPORT (IN_VITRO)"initiation of social spreading requires close association between the two species of bacteria"
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PMID:30700513 - SUPPORT (IN_VITRO)"motility is precluded when a semipermeable membrane is placed between the two colonies"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Exact-composition publication - Pseudomonas-Pedobacter social spreading
Primary publication defining the Pf0-1 plus V48 two-species community and its emergent interspecies social spreading phenotype. |
PHENOTYPE | OTHER | PMID:30700513 |
|
Exact-composition publication - prevalence and variation of social spreading
Follow-up study that revisits the exact Pf0-1 plus V48 pair while testing whether social spreading is conserved among related Pseudomonas fluorescens and Pedobacter isolates. |
PHENOTYPE | OTHER | PMID:34288708 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN How does the demonstrated association requirement produce the joint spreading phenotype?
The existing contact-initiation arrow was attached to Comigration even though its text describes the existing Contact-Dependent Initiation node. It was moved unchanged to that node, repairing the source endpoint without inventing a new causal claim. All three observations and both arrows remain. The primary membrane, adjacent-colony, conditioned-medium and heat-killed-cell results support an association requirement, not a resolved signal or motor. The follow-up abstract reports different requirements for other isolate pairs; these do not override the canonical pair. Non-graph temperature, timing and cross-feeder roles remain #1736.
Attaches to: ecological_interactions#Interspecies Social Spreading, ecological_interactions#Pseudomonas-Pedobacter Comigration, ecological_interactions#Contact-Dependent Initiation
2 evidence item(s)
motility is precluded when a semipermeable membrane is placed between the two colonies
Supports the experimental association requirement without identifying a molecular contact sensor.
While Pf0-1+V48 require low nutrient but high NaCl conditions
Supports the same environment dependence in the exact-pair follow-up study.
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| low-nutrient high-salt hard agar | TSB-NK medium with 2% agar, requiring low nutrient and high NaCl conditions for Pf0-1 plus V48 social spreading | N/A |
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| hard agar surface | 2% agar surface not permissive for monoculture motility | N/A |
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Growth Media
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