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Panzhihua Vanadium Titanium Tailings Community

Ecological State PERTURBED
Environment mine tailings
ENVO:01000650
Source File Panzhihua_Vanadium_Titanium_Tailings.yaml

A perturbed indigenous microbial community from vanadium-titanium magnetite mine tailings in Panzhihua, Sichuan, China, the world's largest V-Ti magnetite deposit and largest vanadium production city. This community comprises nitrogen-fixing rhizobia (Bradyrhizobium pachyrhizi, Rhizobium species), metal-reducing bacteria, and indigenous microbiota that facilitate phytoremediation of polymetallic tailings containing vanadium (340 mg/kg), titanium, iron, copper, nickel, manganese, and zinc. The Panzhihua deposit has generated approximately 570 million tons of tailing slurries from mining activities, creating a massive contamination challenge requiring sustainable bioremediation. The indigenous microbial community has adapted to extreme metal stress through nitrogen fixation coupled with plant growth promotion, enabling successful legume-based phytoremediation with Pongamia pinnata and Leucaena leucocephala. Bradyrhizobium species demonstrate exceptional heavy metal tolerance while maintaining nitrogen-fixing capacity (increasing plant nitrogen content by 10-145%), promoting plant growth through IAA production, and facilitating metal phytoextraction (enhancing Cu and Ni uptake by 600%). Metal-reducing bacteria contribute to vanadium detoxification through dissimilatory V(V) reduction to less soluble V(IV), decreasing vanadium bioavailability and mobilization risk. The community drives transformation of soil organic carbon, increasing active carbon components and carbon transformation enzymes during revegetation, improving overall tailings soil quality. This system represents a critical model for coupling nitrogen fixation, metal tolerance, and phytoremediation in polymetallic mine tailings, addressing both resource recovery and environmental remediation challenges in the world's largest vanadium-titanium deposit.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Bradyrhizobium pachyrhizi NCBITaxon:280333
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
ABUNDANT
Rhizobium selenitireducens NCBITaxon:1286631
PRIMARY_DEGRADER CROSS_FEEDER
COMMON
Rhizobium pisi NCBITaxon:574561
PRIMARY_DEGRADER
RARE
Bacillus species NCBITaxon:1386
PRIMARY_DEGRADER CROSS_FEEDER
DOMINANT
Ochrobactrum intermedium NCBITaxon:194708
SECONDARY_FERMENTER CROSS_FEEDER
COMMON
Polaromonas species NCBITaxon:296
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
COMMON

Ecological Interactions

Nitrogen Fixation and Plant Growth Promotion

MUTUALISM

Source Taxon: Bradyrhizobium pachyrhizi

Metabolites: nitrogen (CHEBI:17997), ammonia (CHEBI:16134), indole-3-acetic acid (CHEBI:16411)

Biological Processes:

Downstream Effects:
→ Soil Organic Carbon Transformation

Evidence

  • doi:10.3389/fmicb.2023.1078333 - SUPPORT (IN_VIVO)
    "Based on the phylogenetic analysis of 16S rRNA and four house-keeping genes ( atpD , recA , rpoB , glnII ), twelve isolates were identified as Bradyrhizobium pachyrhizi , four as Ochrobactrum anthropic , three as Rhizobium selenitireducens and one as Rhizobium pisi"
  • doi:10.3389/fmicb.2023.1078333 - SUPPORT (IN_VIVO)
    "Based on the phylogenetic analysis of 16S rRNA and four house-keeping genes ( atpD , recA , rpoB , glnII ), twelve isolates were identified as Bradyrh"

Metal Phytoextraction and Plant-Microbe Metal Tolerance

MUTUALISM

Source Taxon: Bradyrhizobium pachyrhizi

Metabolites: copper(2+) (CHEBI:29036), nickel(2+) (CHEBI:49786), manganese(2+) (CHEBI:29035), zinc(2+) (CHEBI:29105), 1-aminocyclopropane-1-carboxylate (CHEBI:28930)

Biological Processes:

Evidence

  • doi:10.3389/fmicb.2018.01853 - SUPPORT (IN_VIVO)
    "leucocephala by reducing metal uptake by plants grown in heavy metal-polluted soils"
  • doi:10.3389/fmicb.2023.1078333 - SUPPORT (IN_VIVO)
    "Results Among 57 rhizobia isolated from these nodules, only twenty strains showed different levels of tolerance to copper (Cu), nickel (Ni), manganese (Mn) and zinc (Zn), especially strains PP1 and PP76 showing high tolerance against these four heavy metals"

Dissimilatory Vanadium Reduction and Immobilization

CROSS_FEEDING

Source Taxon: Polaromonas species

Metabolites: vanadate (CHEBI:30019), vanadyl cation (CHEBI:30320), lactate (CHEBI:24996), acetate (CHEBI:30089)

Biological Processes:

Downstream Effects:
→ Vanadium Immobilization via V(IV) Precipitation

Evidence

  • doi:10.1021/acs.est.3c04508 - SUPPORT (IN_VITRO)
    "Microbially mediated V transformation is evaluated to shed light on the primary mechanisms underlying microbial V(V) reduction, namely electron transfer and enzymatic catalysis"
  • PMID:33125214 - SUPPORT (IN_VIVO)
    "Vanadium (V) is an important metal with critical industrial and medical applications"

Soil Organic Carbon Transformation

COMMENSALISM

Metabolites: dissolved organic carbon (CHEBI:16526), cellulose (CHEBI:3961)

Biological Processes:

Downstream Effects:
→ Nitrogen Fixation and Plant Growth Promotion

Evidence

  • doi:10.1016/j.jenvman.2024.122098 - SUPPORT (IN_VIVO)
    "We found that the area mapped as WUI within all four municipalities ranged from about 400 km2 to 1135 km2 depending on the radius size"
  • doi:10.1016/j.jenvman.2024.122098 - SUPPORT (IN_VIVO)
    "As the remediation period of P. pinnata increased, soil active carbon components and carbon transformation related enzymes significantly increased in the V-Ti magnetite tailings"
  • doi:10.1016/j.jenvman.2024.122098 - SUPPORT (IN_VIVO)
    "P. pinnata remediation strengthens carbon sequestration of V-Ti magnetite tailings"

Environmental Factors

Factor Value Unit
pH 6.5-7.5 pH units
Total Vanadium Concentration 340 mg/kg
Polymetallic Contamination Cu 127 mg/kg, Ni 60 mg/kg, Mn 1200 mg/kg, Zn 155 mg/kg mg/kg
Temperature 20-30 °C
Revegetation and Phytoremediation Setup Pongamia pinnata and Leucaena leucocephala legume plantings N/A
Tailings Scale and Origin 570 million tons accumulated metric tons
Indigenous Microbiome Diversity 136 culturable isolates; 58% Bacillus, 21% Rhizobium, 10% Ochrobactrum N/A