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Rifle Uranium-Reducing Community

Ecological State PERTURBED
Environment contaminated soil
ENVO:00002874
Source File Rifle_Uranium_Reducing_Community.yaml

A microbial community stimulated for in situ bioremediation of uranium-contaminated groundwater at the Old Rifle site in Rifle, Colorado. This aquifer community demonstrates sequential reduction processes following acetate biostimulation at 1-3 mM concentrations. The community transitions through distinct metabolic phases: Phase I (days 0-50) dominated by Geobacter species (up to 89% of community) performing Fe(III) reduction coupled to U(VI) reduction, achieving 70% uranium removal within 50 days and reducing concentrations below the EPA treatment goal of 0.18 μM in some wells. Phase II (>50 days) shifts to sulfate-reducing bacteria including Desulfobacteraceae (45% by day 80), Desulfosporosinus, and Desulfotomaculum acetoxidans as Fe(III) becomes depleted. Geobacter metallireducens and Anaeromyxobacter dehalogenans reduce soluble U(VI) to insoluble U(IV), forming biogenic uraninite nanoparticles that immobilize uranium. Desulfovibrio species contribute to uranium reduction through enzymatic pathways while generating hydrogen sulfide that can chemically reduce uranium. This represents the first successful field demonstration of uranium bioremediation via stimulating subsurface Geobacter populations, providing an alternative to pump-and-treat remediation. Groundwater flow rate is 0.82 m/day, creating dynamic conditions where microbial metabolism must outpace uranium advection.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Geobacter species NCBITaxon:28232
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
DOMINANT
Anaeromyxobacter dehalogenans NCBITaxon:161493
SYNTROPHIC_PARTNER
COMMON
Desulfovibrio vulgaris NCBITaxon:881
SECONDARY_FERMENTER SYNTROPHIC_PARTNER
COMMON
Desulfosporosinus species NCBITaxon:79206
SECONDARY_FERMENTER
COMMON
Desulfobacteraceae family NCBITaxon:213118
PRIMARY_DEGRADER
DOMINANT

Ecological Interactions

Acetate Oxidation Coupled to Fe(III) and U(VI) Reduction

CROSS_FEEDING

Source Taxon: Geobacter species

Metabolites: acetate (CHEBI:30089), uranium(VI) (CHEBI:37119), uranium(IV) (CHEBI:33395), Fe(III) (CHEBI:29034), Fe(II) (CHEBI:29033)

Biological Processes:

Downstream Effects:
→ Uranium Immobilization via Uraninite Formation

Evidence

  • PMID:14532040 - SUPPORT (IN_VIVO)
    "As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed"
  • PMID:14532040 - SUPPORT (IN_VIVO)
    "Within 50 days uranium had declined below the prescribed treatment level"
  • PMID:14532040 - SUPPORT (IN_VIVO)
    "At 17 days after the start of the acetate injection Geobacteraceae accounted for 89% of the groundwater microbial community"

Uranium Immobilization via Uraninite Formation

MUTUALISM

Metabolites: uranium(IV) (CHEBI:33395)

Biological Processes:

Evidence

  • PMID:14532040 - SUPPORT (IN_VIVO)
    "Analysis of 16S ribosomal DNA (rDNA) sequences and phospholipid fatty acid profiles demonstrated that the initial loss of uranium from the groundwater was associated with an enrichment of Geobacter species in the treatment zone"

Hydrogen-Mediated U(VI) Reduction by Anaeromyxobacter

SYNTROPHY

Source Taxon: Anaeromyxobacter dehalogenans

Metabolites: dihydrogen (CHEBI:18276), uranium(VI) (CHEBI:37119), uranium(IV) (CHEBI:33395)

Biological Processes:

Evidence

  • PMID:18843300 - SUPPORT (IN_VITRO)
    "Thirty-four c-type cytochrome genes were upregulated in the sediment-grown cells, including several genes that are homologous to cytochromes that are required for optimal Fe(III) and U(VI) reduction by G"

Sulfate Reduction and Chemical U(VI) Reduction

CROSS_FEEDING

Source Taxon: Desulfobacteraceae family

Metabolites: sulfate (CHEBI:16189), hydrogen sulfide (CHEBI:16136), uranium(VI) (CHEBI:37119), uranium(IV) (CHEBI:33395)

Biological Processes:

Evidence

  • PMID:14532040 - SUPPORT (IN_VIVO)
    "Organisms with 16S rDNA sequences most closely related to those of sulfate reducers became predominant, and Geobacter species became a minor component of the community"

Community Succession from Metal to Sulfate Reduction

COMPETITION

Metabolites: Fe(III) (CHEBI:29034), sulfate (CHEBI:16189)

Biological Processes:

Evidence

  • PMID:14532040 - SUPPORT (IN_VIVO)
    "As the acetate injection continued over 50 days there was a loss of sulfate from the groundwater and an accumulation of sulfide and the composition of the microbial community changed"
  • PMID:14532040 - SUPPORT (IN_VIVO)
    "Fe(III) is depleted, sulfate is reduced, and sulfate-reducing bacteria predominate"

Environmental Factors

Factor Value Unit
pH ~7 pH units
Oxygen Availability Anaerobic after acetate amendment qualitative
Acetate Concentration 1-3 mM
Groundwater Flow Rate 0.82 m/day
Initial Uranium Concentration 0.4-1.4 μM
Time to Uranium Removal 9-50 days