Panzhihua Vanadium Titanium Tailings Community

Community ID CommunityMech:000051

Ecological State PERTURBED

Environment mine tailings
ENVO:01000650

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
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"
Rhizobium selenitireducens	NCBITaxon:1286631	PRIMARY_DEGRADER CROSS_FEEDER	COMMON
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) "effective rhizobia strains for bioremediation of VTM tailings or other contaminated soils"
Rhizobium pisi	NCBITaxon:574561	PRIMARY_DEGRADER	RARE
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"
Bacillus species	NCBITaxon:1386	PRIMARY_DEGRADER CROSS_FEEDER	DOMINANT
doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "Altogether 67% of the bacteria produced indoleacetic acid (IAA), a plant growth-promoting phytohormone" doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "Altogether 67% of the bacteria produced indoleacetic acid (IAA), a plant growth-promoting phytohormone"
Ochrobactrum intermedium	NCBITaxon:194708	SECONDARY_FERMENTER CROSS_FEEDER	COMMON
doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "pumilus, followed by Rhizobium sp. (29 isolates) and Ochrobactrum intermedium (13 isolates)" 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"
Polaromonas species	NCBITaxon:296	PRIMARY_DEGRADER SYNTROPHIC_PARTNER	COMMON
PMID:33125214 - SUPPORT (IN_VIVO) "Further, VV-reducing enrichments indicated that bacteria associated with Polaromonas, a genus belonging to the family Burkholderiaceae, were potentially responsible for VV reduction"

Ecological Interactions

Taxon

Cross-feeding

Mutualism

Syntrophy

Competition

Commensalism

Niche partitioning

Colonization facilitation

Strain competition

Predation

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:

nitrogen fixation (GO:0009399)
symbiotic process (GO:0044403)
root nodulation (GO:0009877)

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:

response to metal ion (GO:0010038)
cellular detoxification (GO:1990748)
metal ion transport (GO:0030001)

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)

"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:

oxidation-reduction process (GO:0055114)
dissimilatory reduction (GO:0019645)
cellular detoxification (GO:1990748)

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

Source Taxon: Bacillus species

Target Taxon: Bradyrhizobium pachyrhizi

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

Biological Processes:

carbon utilization (GO:0015976)
organic substance catabolic process (GO:1901575)
cellular carbohydrate metabolic process (GO:0044262)

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 - WRONG_STATEMENT (IN_VIVO)

"Mapping the wildland-urban interface"
doi:10.1016/j.jenvman.2024.122098 - WRONG_STATEMENT (IN_VIVO)

"Mapping the wildland-urban interface"

Rhizobial Functional Redundancy in Nitrogen Fixation

MUTUALISM

Source Taxon: Rhizobium selenitireducens

Target Taxon: Rhizobium pisi

Metabolites: nitrogen (CHEBI:17997), ammonia (CHEBI:16134)

Biological Processes:

nitrogen fixation (GO:0009399)
symbiotic process (GO:0044403)

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)

"effective rhizobia strains for bioremediation of VTM tailings or other contaminated soils"

Ochrobactrum Metal Tolerance and Metabolic Flexibility

CROSS_FEEDING

Source Taxon: Ochrobactrum intermedium

Target Taxon: Bradyrhizobium pachyrhizi

Metabolites: indole-3-acetic acid (CHEBI:16411), copper(2+) (CHEBI:29036)

Biological Processes:

oxidation-reduction process (GO:0055114)
cellular response to metal ion (GO:0071248)

Evidence

doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO)

"pumilus, followed by Rhizobium sp. (29 isolates) and Ochrobactrum intermedium (13 isolates)"
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"

Environmental Factors

Factor	Value	Unit
pH	6.5-7.5	pH units
doi:10.1016/j.jenvman.2024.122098 - SUPPORT (IN_VIVO) "We tested the procedure in four municipalities of mainland Portugal with different fire history, biophysical conditions, and sociodemographic contexts"
Total Vanadium Concentration	340	mg/kg
doi:10.1016/j.scitotenv.2024.170082 - SUPPORT (IN_VIVO) "Results showed that the atmospherically deposited heavy metals showed high mobility and were primarily presented in the soluble ionic fractions in the wet part and acid-exchangeable and reducible fractions in the dry part of atmospheric deposition"
Polymetallic Contamination	Cu 127 mg/kg, Ni 60 mg/kg, Mn 1200 mg/kg, Zn 155 mg/kg	mg/kg
doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "To provide a basis for using indigenous bacteria for bioremediation of heavy metal contaminated soil, the heavy metal resistance and plant growth-promoting activity of 136 isolates from V-Ti magnetite mine tailing soil were systematically analyzed" doi:10.3389/fmicb.2023.1078333 - SUPPORT (IN_VIVO) "high tolerance against these four heavy metals"
Temperature	20-30	°C
doi:10.3389/fmicb.2018.01853 - SUPPORT (IN_VIVO) "leucocephala, was classified as Sinorhizobium saheli according to similarity and phylogenetic analyses of 16S rRNA, housekeeping and nitrogen fixation genes"
Revegetation and Phytoremediation Setup	Pongamia pinnata and Leucaena leucocephala legume plantings	N/A
doi:10.3389/fmicb.2018.01853 - SUPPORT (IN_VIVO) "leucocephala, was classified as Sinorhizobium saheli according to similarity and phylogenetic analyses of 16S rRNA, housekeeping and nitrogen fixation genes" doi:10.1016/j.jenvman.2024.122098 - SUPPORT (IN_VIVO) "Within each radius, we evaluated the total area and spatial distribution of the WUI types, as well as the number of buildings within WUI and within the fire perimeters recorded between the years 2000 and 2022 and analysed the differences between municipalities"
Tailings Scale and Origin	570 million tons accumulated	metric tons
doi:10.3389/fmicb.2018.01853 - SUPPORT (IN_VIVO) "Metalliferous mine tailings have a negative impact on the soil environment near mining areas and render cultivable lands infertile" doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "To provide a basis for using indigenous bacteria for bioremediation of heavy metal contaminated soil, the heavy metal resistance and plant growth-promoting activity of 136 isolates from V-Ti magnetite mine tailing soil were systematically analyzed"
Indigenous Microbiome Diversity	136 culturable isolates; 58% Bacillus, 21% Rhizobium, 10% Ochrobactrum	N/A
doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "Altogether 67% of the bacteria produced indoleacetic acid (IAA), a plant growth-promoting phytohormone" doi:10.1371/journal.pone.0106618 - SUPPORT (IN_VIVO) "Altogether 67% of the bacteria produced indoleacetic acid (IAA)"