Propane-enriched aerobic mixed cultures derived from three Michigan State University Long-Term Ecological Research agricultural soils (Soils T2, T3, T4) and from impacted-site sediment at a West Coast Naval Station (Site 1), evaluated for cometabolic biodegradation of three chlorinated ethenes - trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), and 1,1-dichloroethene (1,1-DCE) - in the presence of propane as growth substrate. Substrate-specific selection drove distinct dominance patterns: cDCE-amended cultures were dominated by Mycolicibacterium followed by Mycobacterium, TCE-amended cultures were dominated by Rhodococcus (R. opacus or R. wratislaviensis from agricultural soils; Mycolicibacterium/Mycobacterium/Rhodococcus mixture from the impacted site sediment), and the subset of 1,1-DCE-degrading cultures was dominated by Pseudonocardia (with a truncated propane monooxygenase alpha subunit suggesting alternative enzymes drive 1,1-DCE transformation). The enrichments express group 5 (prmABCD) and putative group 6 propane monooxygenases. The system supports development of propane-based bioaugmentation strategies for mixed chlorinated solvent contamination under aerobic conditions.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Rhodococcus opacus | NCBITaxon:37919 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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DOMINANT |
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| Rhodococcus wratislaviensis | NCBITaxon:44752 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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DOMINANT |
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| Mycolicibacterium | NCBITaxon:1866885 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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DOMINANT |
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| Mycobacterium | NCBITaxon:1763 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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COMMON |
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| Pseudonocardia | NCBITaxon:1847 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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DOMINANT |
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| Pseudonocardia broussonetiae | NCBITaxon:2736640 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
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COMMON |
| Methylibium | NCBITaxon:316612 · TaxonMech · TraitMech |
CROSS_FEEDER
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RARE |
| unclassified Burkholderiaceae — ontology label: Burkholderiaceae | NCBITaxon:119060 · TaxonMech · TraitMech |
CROSS_FEEDER
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RARE |
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.
TCE Removal in Rhodococcus-Dominated Enrichments
Propane-enriched mixed cultures sustained TCE degradation and were dominated by Rhodococcus; recovered MAGs were classified as R. opacus or R. wratislaviensis. PARTIAL: abundance and monooxygenase genes do not assign the measured community transformation to a particular taxon or enzyme. Gene expression was not examined.
Participating Taxa: Rhodococcus opacus, Rhodococcus wratislaviensis
Metabolites: trichloroethene (CHEBI:16602 · MediaIngredientMech · CMMMech), propane (CHEBI:32879 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellular response to xenobiotic stimulus (GO:0071466 · PathwayMech)
Evidence
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doi:10.1016/j.jenvman.2026.129957 - SUPPORT (IN_VITRO)"TCE-degrading cultures were dominated by Rhodococcus"
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doi:10.1016/j.jenvman.2026.129957 - SUPPORT (COMPUTATIONAL)"Functional gene analysis identified both group 5 (prmABCD) and putative group 6 propane monooxygenases"
cDCE Removal in Mycobacterium and Mycolicibacterium Enrichments
Propane-enriched mixed cultures sustained cDCE degradation and were dominated by Mycobacterium and Mycolicibacterium. PARTIAL: genus abundance does not establish which organisms or enzymes performed the community transformation. The accessible abstract does not establish an interspecies transfer route.
Participating Taxa: Mycolicibacterium, Mycobacterium
Metabolites: cis-1,2-dichloroethene (CHEBI:18882 · MediaIngredientMech · CMMMech), propane (CHEBI:32879 · MediaIngredientMech · CMMMech)
Biological Processes:
- cellular response to xenobiotic stimulus (GO:0071466 · PathwayMech)
Evidence
-
doi:10.1016/j.jenvman.2026.129957 - SUPPORT (IN_VITRO)"cDCE-degrading cultures being dominated by Mycobacterium and Mycolicibacterium"
Substrate-Specific Selection Across Chlorinated Ethenes
Different chlorinated substrates were associated with distinct enrichment compositions and degradation behavior. Preserve the reported substrate-dependent selection without equating environmental filtering with demonstrated competition among guilds. This record combines separate enrichment treatments, not one fixed community.
Metabolites: trichloroethene (CHEBI:16602 · MediaIngredientMech · CMMMech), cis-1,2-dichloroethene (CHEBI:18882 · MediaIngredientMech · CMMMech), 1,1-dichloroethene (CHEBI:34031 · MediaIngredientMech · CMMMech)
Biological Processes:
- response to xenobiotic stimulus (GO:0009410 · PathwayMech)
PARTIAL: substrate-specific selection is the authors explanation for Rhodococcus-dominated communities sustaining TCE transformation. The abstract supports the treatment-linked structure/function pattern, not isolated taxon or enzyme mediation.
PARTIAL: substrate-specific selection is the authors explanation for Mycobacterium/Mycolicibacterium-dominated communities sustaining cDCE transformation. Dominance does not identify the active organism or monooxygenase.
Evidence
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doi:10.1016/j.jenvman.2026.129957 - SUPPORT (IN_VITRO)"Whole genome sequencing analyses revealed pronounced substrate-dependent selection of microbial communities"
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doi:10.1016/j.jenvman.2026.129957 - SUPPORT (IN_VITRO)"substrate-specific pressures govern propanotrophic community structure and function, and highlight distinct roles of key actinobacterial genera in chlorinated ethene cometabolism"
1,1-DCE-Driven Inhibition of Propanotrophs
1,1-DCE removal occurred in only some enrichments, took longer over transfers and was absent at elevated concentrations. PARTIAL: these observations are consistent with inhibitory or toxic effects, not demonstrated interspecies competition or an identified toxic agent.
Metabolites: 1,1-dichloroethene (CHEBI:34031 · MediaIngredientMech · CMMMech), propane (CHEBI:32879 · MediaIngredientMech · CMMMech)
Biological Processes:
- response to xenobiotic stimulus (GO:0009410 · PathwayMech)
HYPOTHESIZED: inhibition could contribute to substrate-dependent selection by restricting community function. The abstract does not isolate toxicity as the cause of taxonomic replacement.
Evidence
-
doi:10.1016/j.jenvman.2026.129957 - SUPPORT (IN_VITRO)"1,1-DCE removal was absent at elevated concentrations, both trends consistent with inhibitory or toxic effects"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which activities connect substrate selection to measured mixed-culture transformation?
Retain all four findings and three existing directions with explicit inference bounds. Only the fresh primary abstract was accessible. Monooxygenase expression was not examined; taxon dominance is not enzyme activity or partner exchange. Detailed kinetic and operon assertions outside this graph remain part of #765 after paywalled-body removal under #754. Missing access is not evidence that experiments were absent. No new nodes or directions were added.
Attaches to: ecological_interactions#TCE Removal in Rhodococcus-Dominated Enrichments, ecological_interactions#cDCE Removal in Mycobacterium and Mycolicibacterium Enrichments, ecological_interactions#Substrate-Specific Selection Across Chlorinated Ethenes, ecological_interactions#1,1-DCE-Driven Inhibition of Propanotrophs
2 evidence item(s)
Functional gene analysis identified both group 5 (prmABCD) and putative group 6 propane monooxygenases
Supports community monooxygenase gene content, not taxon-specific enzyme expression, activity or cross-feeding.
1,1-DCE removal was absent at elevated concentrations, both trends consistent with inhibitory or toxic effects
Supports restricted removal consistent with inhibition, not proof of the toxic agent or selection mechanism.
External Resources
| Name | Repository | Resource ID |
|---|---|---|
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Primary publication
Faghihinezhad, Eshghdoostkhatami, Cupples 2026 Journal of Environmental Management - "Characterization of multiple trichloroethene, cis-dichloroethene and 1,1-dichloroethene degrading propanotrophic communities". Subscription access; no copy is held in this repository (#754). |
OTHER | doi:10.1016/j.jenvman.2026.129957 |
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Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| Propane as growth substrate | 0.8-1.2 mg/L per amendment | N/A |
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| Chlorinated ethene contaminant concentration | TCE and cDCE at 4-5 mg/L; 1,1-DCE at 0.5-1 mg/L | N/A |
| Inoculum source | KBS-LTER agricultural soils T2/T3/T4 + West Coast Naval Station Site 1 sediment | N/A |
| Aerobic incubation | orbital shaker at 120 rpm, room temperature | N/A |
Growth Media
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