A laboratory four-species bacterial biofilm model derived from an industrial milk pasteurization-line biofilm. The community contains Rhodocyclus sp., Pseudomonas fluorescens, Kocuria varians, and Bacillus cereus, forms reproducible biofilms, and was used to resolve dynamic positive and negative interspecies interactions, including a Bacillus cereus thiocillin I-mediated negative interaction that shapes species distribution and robustness.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Rhodocyclus sp. — ontology label: Rhodocyclus | NCBITaxon:1064 · TaxonMech · TraitMech |
CROSS_FEEDER
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N/A |
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| Pseudomonas fluorescens | NCBITaxon:294 · TaxonMech · TraitMech |
CROSS_FEEDER
|
N/A |
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| Kocuria varians | NCBITaxon:1272 · TaxonMech · TraitMech |
CROSS_FEEDER
|
N/A |
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| Bacillus cereus | NCBITaxon:1396 · 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.
Biofilm Community Composition and Growth Interactions
Controlled species-subset biofilms and fitted growth curves support dynamic positive and negative effects in this four-species model. Rhodocyclus adhesion/early growth was facilitated, Pseudomonas development was delayed, and Kocuria abundance was suppressed. These distinct measured effects do not establish a community-wide cooperation benefit, competitive niche partitioning or a resolved physical shielding mechanism. Bacillus ATCC14579T was a laboratory substitution; canonical strain labels are preserved.
Participating Taxa: Rhodocyclus sp., Pseudomonas fluorescens, Kocuria varians, Bacillus cereus
Biological Processes:
- biofilm formation (GO:0042710 · PathwayMech)
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Evidence
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doi:10.1002/mbo3.1254 - SUPPORT (IN_VITRO)"network of dynamic, positive, and negative interactions"
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doi:10.1002/mbo3.1254 - SUPPORT (IN_VITRO)"determine the final composition of the biofilm"
Thiocillin-Biosynthesis-Dependent Kocuria Suppression
B. cereus tclE-H deletion removed anti-Kocuria activity in the plate assay and, when substituted into the four-species biofilm, increased Kocuria abundance by about 50-fold. This is positive genetic evidence for thiocillin-biosynthesis-dependent suppression, interpreted by the authors as thiocillin I action. Activity was mainly pellet-associated or unstable; a freely diffusible bulk-medium route is not established. The main text did not report complementation or a purified-thiocillin rescue. The observed negative growth effect does not require reciprocal harm to Bacillus.
Participating Taxa: Bacillus cereus, Kocuria varians
Biological Processes:
- interspecies interaction between organisms (GO:0044419 · PathwayMech)
Replacing wild-type B. cereus with the tclE-H deletion mutant increased Kocuria abundance and changed the 72-hour four-species composition, supporting a causal contribution of the thiocillin-biosynthesis-dependent negative interaction under the tested biofilm conditions. This does not establish every mechanism in the wider interaction network.
The tclE-H mutant substitution changed the community response to initial Bacillus depletion and to continuous substrate/medium changes. The genetic intervention supports a condition-specific contribution to the measured response, not universal robustness, a mature-biofilm recovery trajectory or a fully isolated thiocillin I rescue mechanism.
Evidence
-
PMID:34964290 - SUPPORT (IN_VITRO)"thiocillin I synthesized by the B. cereus strain"
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PMID:34964290 - SUPPORT (IN_VITRO)"impact on robustness by mutational analysis"
Condition-Specific Biofilm Response to Perturbation
Wild-type biofilms established similar 72-hour compositions after the tested initial physiological-state and Bacillus-inoculum changes, while glass substitution and especially undiluted medium altered the community. The thiocillin-biosynthesis mutant changed responses to particular transient and continuous perturbations. This is an endpoint comparison during establishment, not a recovery time course after disrupting an already mature biofilm, a general colonization-facilitation mechanism or robustness to every disturbance. Neither community resisted strong continuous changes uniformly.
Participating Taxa: Rhodocyclus sp., Pseudomonas fluorescens, Kocuria varians, Bacillus cereus
Biological Processes:
- biofilm formation (GO:0042710 · PathwayMech)
Evidence
-
doi:10.1002/mbo3.1254 - SUPPORT (IN_VITRO)"highly robust against initial, transient perturbations"
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doi:10.1002/mbo3.1254 - SUPPORT (IN_VITRO)"less so towards continuous perturbations"
Associated Datasets
| Dataset | Type | Repository | Accession |
|---|---|---|---|
|
Four-species model biofilm publication and raw-data resource
Publication reporting species-resolved biofilm growth, perturbation robustness, interaction inference, and mutational analysis of a four-species dairy-processing biofilm model. |
PHENOTYPE | OTHER | PMID:34964290 |
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which molecular and spatial mechanisms determine the condition-specific biofilm response?
Retain both genetic-intervention arrows and positive omission/growth findings. The assay distinguishes initial/transient from continuous changes; it is not a mature-biofilm recovery experiment. Purified-molecule or complementation controls would further separate thiocillin I from biosynthetic-locus effects, without negating the existing knockout evidence. Protection of Kocuria by the other members could involve spatial shielding or adsorption but was not selectively resolved. Canonical Pseudomonas CLL49 spelling is preserved despite CCL49 elsewhere in the paper. Prior cultivation-arm correction under #529 remains unchanged. Non-graph taxon roles and origin claims are preserved, not recertified.
Attaches to: ecological_interactions#Biofilm Community Composition and Growth Interactions, ecological_interactions#Thiocillin-Biosynthesis-Dependent Kocuria Suppression, ecological_interactions#Condition-Specific Biofilm Response to Perturbation
External Resources
| Name | Repository | Resource ID |
|---|---|---|
|
PNDB raw data page for dynamic four-species model biofilm
Public raw-data landing page associated with the four-species model biofilm publication. |
OTHER | PMID:34964290 |
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| industrial milk pasteurization-line source | biofilm from a gasket in a milk pasteurization line | N/A |
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| tryptic soy cultivation | Tryptic soy agar and tryptic soy broth at 30 C | N/A |
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Growth Media
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