identifier: traitmech:000012
label: metal tolerant
definition: An environmental tolerance in which an organism grows in the presence
  of elevated concentrations of toxic heavy-metal or metalloid ions, typically via
  efflux-based resistance determinants (RND-family CBA pumps, P-type ATPases, and
  cation diffusion facilitators).
definition_source: PMID:12829273
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000059
synonyms:
- synonym_text: metallophilic
  synonym_type: RELATED_SYNONYM
  source: DOI:10.3389/fmicb.2020.00047
- synonym_text: heavy metal resistant
  synonym_type: RELATED_SYNONYM
  source: PMID:12829273
evidence:
- reference: PMID:12829273
  snippet: CBA efflux pumps driven by proteins of the resistance-nodulation-cell division
    superfamily, P-type ATPases, cation diffusion facilitator and chromate proteins
  notes: Review of efflux-mediated heavy-metal resistance supports active metal export
    as the dominant prokaryotic tolerance mechanism.
- reference: DOI:10.3389/fmicb.2020.00047
  snippet: This metallophilic strain BS1, harbors numerous gene clusters encoding
    metal-resistance determinants enabling detoxification of transition metal ions
    and complexes
  notes: 'Organism example: Cupriavidus metallidurans is the model metallophilic bacterium
    tolerating many toxic metals via dedicated resistance gene clusters.'
canonical_examples:
- taxon_id: NCBITaxon:119219
  taxon_label: Cupriavidus metallidurans
  note: "Paradigm heavy-metal-resistance bacterium (strain CH34; plasmid-borne metal-efflux determinants)."
  reference: PMID:20463976
causal_graphs:
- graph_id: metal_tolerance_efflux_detoxification
  title: Metal tolerance via active efflux of heavy-metal ions
  description: Evidence-backed causal sketch linking heavy-metal exposure to efflux-pump-mediated
    detoxification underlying broad metal tolerance.
  nodes:
  - node_id: metal_tolerant_trait
    label: metal tolerant
    node_type: TRAIT
    grounding: traitmech:000012
    description: Capacity to grow at elevated heavy-metal or metalloid concentrations.
  - node_id: heavy_metal_ion
    label: toxic heavy-metal ion
    node_type: ENVIRONMENTAL_FACTOR
    description: Cytoplasmic excess of a transition-metal or metalloid cation.
  - node_id: efflux_pump
    label: metal efflux pump
    node_type: GENE_OR_PROTEIN
    description: RND-family CBA pumps, P-type ATPases, and cation diffusion facilitators
      exporting metals.
    grounding: UniProtKB:A0A067YD12
  - node_id: metal_ion_export
    label: metal ion transmembrane export
    node_type: BIOLOGICAL_PROCESS
    grounding: GO:0030001
    description: Transport of metal cations across the cytoplasmic membrane.
  - node_id: arsenate
    label: arsenate As(V)
    node_type: CHEMICAL
    description: Oxidized arsenic oxyanion taken up by phosphate transporters.
  - node_id: arsenite
    label: arsenite As(III)
    node_type: CHEMICAL
    description: Reduced arsenic species substrate for arsenite efflux pumps.
  - node_id: arsc_reductase
    label: ArsC arsenate reductase
    node_type: GENE_OR_PROTEIN
    description: Cytoplasmic reductase converting arsenate to arsenite prior to extrusion.
  - node_id: ars_operon
    label: ars operon
    node_type: GENE_OR_PROTEIN
    description: arsC reductase plus arsB/acr3 arsenite efflux determinant cluster.
  - node_id: arsenic_tolerance
    label: arsenic tolerance
    node_type: STATE
    description: Detoxification-mediated tolerance of arsenic oxyanions.
  edges:
  - subject: heavy_metal_ion
    predicate: challenges
    object: metal_tolerant_trait
    description: Elevated heavy-metal concentrations are the environmental challenge
      the trait counters.
    evidence:
    - reference: DOI:10.3389/fmicb.2020.00047
      notes: Cupriavidus metallidurans encodes many metal-resistance determinants
        confronting multiple toxic metals.
    predicate_id: METPO:2007406
  - subject: efflux_pump
    predicate: enables
    object: metal_ion_export
    description: CBA pumps, P-type ATPases, and CDFs export toxic metal cations from
      the cytoplasm.
    evidence:
    - reference: PMID:12829273
      notes: Nies reviews efflux-mediated heavy-metal resistance as the dominant prokaryotic
        tolerance mechanism.
    predicate_id: RO:0002327
  - subject: metal_ion_export
    predicate: enables
    object: metal_tolerant_trait
    description: Cytoplasmic detoxification by export realizes the metal-tolerant
      phenotype.
    evidence:
    - reference: PMID:12829273
      notes: Nies frames efflux-based export as the basis of broad heavy-metal tolerance.
    predicate_id: RO:0002327
  - subject: arsc_reductase
    predicate: converts
    object: arsenate
    description: ArsC arsenate reductase reduces As(V) to As(III) as the first detoxification
      step.
    evidence:
    - reference: DOI:10.52700/jmmg.v5i1.155
      notes: 'Review: "ArsC converting As(V) to As(III) followed by extrusion"; general
        across bacteria.'
  - subject: arsenate
    predicate: is converted to
    object: arsenite
    description: Arsenate is reduced to arsenite, the species handled by efflux pumps.
    evidence:
    - reference: DOI:10.52700/jmmg.v5i1.155
      notes: 'Review: ArsC converts As(V) to As(III) followed by extrusion.'
  - subject: ars_operon
    predicate: enables
    object: arsenic_tolerance
    description: The arsC + arsB/acr3 ars operon mediates arsenate reduction and arsenite
      extrusion conferring arsenic tolerance.
    evidence:
    - reference: DOI:10.7717/peerj.18383
      notes: '"a cooperative mechanism involving detoxification through arsenate reduction"
        via arsC/arsA/arsB/acr3 genes across mixed soil taxa.'
    predicate_id: RO:0002327
  - subject: arsenic_tolerance
    predicate: is a
    object: metal_tolerant_trait
    description: Arsenic (metalloid) tolerance is a component of the broad metal-tolerant
      phenotype.
    evidence:
    - reference: DOI:10.52700/jmmg.v5i1.155
      notes: Arsenic detoxification (reduction + efflux) is part of generic bacterial
        heavy-metal/metalloid resistance.
    predicate_id: rdfs:subClassOf
  - subject: efflux_pump
    predicate: mediates
    object: metal_tolerant_trait
    description: P-type ATPase, CDF, and RND efflux transporters mediate heavy-metal
      resistance in most bacteria.
    evidence:
    - reference: DOI:10.52700/jmmg.v5i1.155
      notes: '"resistance in most bacteria is mediated by P-type ATPase efflux, diffusion
        facilitator transporters of cations and RND" - generic review.'
curation_history:
- timestamp: '2026-05-28T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate ENVIRONMENT trait (general heavy-metal/metalloid tolerance)
    from literature research to fill the metal-tolerance coverage gap. Parent of the
    metal-specific sub-variants.
  llm_assisted: true
- timestamp: '2026-06-09T14:00:00Z'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added evidence-backed causal graph (efflux-mediated metal detoxification)
    with GO node grounding and RO/METPO predicate groundings; promoted PROPOSED to
    REVIEWED.
  llm_assisted: true
- timestamp: '2026-06-14T06:38:14Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (UniProtKB:A0A067YD12×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 5 evidence-backed generic edges (5 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:10Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×1, rdfs:subClassOf×1).
  llm_assisted: true