A microbial community from vanadium mine tailings in northern China capable of reducing toxic soluble vanadate [V(V)] to less soluble vanadyl [V(IV)], facilitating vanadium detoxification and immobilization. This community is dominated by Polaromonas species (Burkholderiaceae family, up to 46% relative abundance in tailings) that perform dissimilatory V(V) reduction using genes homologous to iron and metal reduction pathways (cymA, omcA, narG). The tailings harbor diverse metal-reducing bacteria including sulfate reducers (Desulfovibrio, Desulfitobacterium) and iron-reducing Proteobacteria (Geobacter-related organisms) that contribute to reductive immobilization of vanadium and co-occurring metals. V(V) reduction to V(IV) decreases vanadium solubility by 2-3 orders of magnitude, transforming mobile vanadate into sparingly soluble vanadyl species and V(IV)-containing minerals. The community is enriched from highly contaminated mine tailings with total vanadium concentrations reaching 10,500 mg/kg and bioavailable V(V) at 15-25 mg/L in pore water. Under anaerobic conditions with electron donors (lactate, acetate, hydrogen), the community achieves 60-85% V(V) reduction within 7-14 days. Genes encoding c-type cytochromes (cymA, omcA), nitrate reductases (narG, napA), and arsenate reductases (arrA) mediate V(V) reduction through outer membrane electron transfer pathways. This represents the first demonstration of microbial V(V) reduction in circumneutral pH mine tailings, providing a biological approach for vanadium immobilization and mine remediation. The system is particularly relevant for emerging vanadium contamination from steel production, petroleum processing, and vanadium redox flow battery manufacturing.
Taxonomy
| Taxon | Ontology ID | Functional Roles | Abundance |
|---|---|---|---|
| Polaromonas species — ontology label: Polaromonas | NCBITaxon:52972 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
|
DOMINANT |
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| Desulfovibrio species — ontology label: Desulfovibrio | NCBITaxon:872 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
SYNTROPHIC_PARTNER
|
COMMON |
|
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| Geobacter species — ontology label: Geobacter metallireducens | NCBITaxon:28232 · TaxonMech · TraitMech |
PRIMARY_DEGRADER
SYNTROPHIC_PARTNER
|
COMMON |
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| Desulfitobacterium species — ontology label: Desulfitobacterium | NCBITaxon:36853 · TaxonMech · TraitMech |
SECONDARY_FERMENTER
|
COMMON |
|
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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.
Vanadium Reduction in Polaromonas-Associated Enrichments
V(V)-reducing enrichments support community-level reduction. PARTIAL: enrichment association implicates Polaromonas, and its recovered MAGs suggest cymA, omcA and narG involvement; these observations do not establish a purified-isolate activity, gene necessity or a partner-specific respiratory pathway. Public Supplement Figure S2 shows 6 mM acetate and 1.5 mM vanadate treatments with autoclaved and no-vanadate controls. No unsupported arrA function, energy yield, time course or numerical removal rate is assigned.
Participating Taxa: Polaromonas species
Reduction of supplied V(V) yields V(IV), which precipitated in the acetate-plus-vanadate enrichments shown in Supplement Figure S2. This existing direction is retained at community scale; attribution specifically to Polaromonas remains PARTIAL, and the controls do not prove a particular reductase or mineral identity.
Evidence
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PMID:33125214 - SUPPORT (IN_VITRO)"were potentially responsible for VV reduction"
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PMID:33125214 - SUPPORT (COMPUTATIONAL)"Retrieved metagenome-assembled genomes (MAGs) suggested"
V(IV) Precipitation in Reducing Enrichments
Public Supplement Figure S2 reports V(IV) precipitate formation in acetate-plus-vanadate enrichment treatments and not in the autoclaved or no-vanadate controls. Preserve the positive enrichment-level precipitation observation. Polaromonas is the proposed associated genus, not a proven sole producer; no mineral phase, XAS fraction, solubility constant, oxidation stability or reciprocal microbial fitness benefit is established here.
Participating Taxa: Polaromonas species
Evidence
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PMID:33125214 - SUPPORT (IN_VITRO)"which formed VIV precipitates"
Knowledge gaps & discussions (1)
KNOWLEDGE_GAP OPEN Which organisms and enzymes actually mediate enrichment reduction and precipitation?
Keep positive V(V) reduction and treatment-associated V(IV) precipitation. MAG function and Polaromonas responsibility remain inferred; co-occurrence networks and annotated nitrogen/sulfur pathways are not transfer or enzyme-perturbation evidence. The reviewed primary abstract and public SI do not support the removed Desulfovibrio-to-Desulfitobacterium sulfide or Geobacter-to-Polaromonas sequential-iron routes and their exact numbers. Main text remains inaccessible. Only Polaromonas is explicitly credited in these qualified community nodes; the other canonical members remain unverified and may appear disconnected. Non-graph taxonomy, numerical claims and Panzhihua/Sichuan locality need #1716; public Figure S1 shows Hunan, and PMID19077236 concerns an Acidithiobacillus ferrooxidans genome, not Geobacter vanadium reduction. Related #1680 concerns a different record.
Attaches to: ecological_interactions#Vanadium Reduction in Polaromonas-Associated Enrichments, ecological_interactions#V(IV) Precipitation in Reducing Enrichments
2 evidence item(s)
were potentially responsible for VV reduction
The abstract proposes Polaromonas involvement in reducing enrichments; taxon attribution is not a gene or isolate perturbation.
which formed VIV precipitates
Primary public Supplement Figure S2, not the abstract: treatment-associated precipitation with autoclaved/no-vanadate controls. This does not resolve mineral identity or sole-organism causation.
Environmental Factors
| Factor | Value | Unit |
|---|---|---|
| pH | 6.5-7.5 | pH units |
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| Total Vanadium Concentration | 10,500 | mg/kg |
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| Dissolved V(V) Concentration | 15-25 | mg/L |
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| Redox Potential | -50 to -150 | mV |
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| Electron Donor Concentration | 5-20 mM lactate; 2-10 mM acetate | mM |
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| Temperature | 15-25 | °C |
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| Time to V(V) Reduction | 7-14 | days |
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| Sulfate Concentration | 500-2000 | mg/L |
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