identifier: METPO:1000805
label: Electron transfer
definition: A metabolism in which electrons are transferred from an electron donor
  to an electron acceptor.
definition_source: DOI:10.1016/j.bbabio.2008.09.008
trait_category: METABOLISM
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000060
created_by: Jed Dongjin Kim-Ozaeta
evidence:
- reference: DOI:10.1016/j.bbabio.2008.09.008
  snippet: electron transfer process
  notes: Review supports electron donor-to-acceptor flow in membrane respiratory chains.
- reference: DOI:10.1038/nrmicro.2016.93
  snippet: c-type cytochromes and microbial nanowires
  notes: Review supports extracellular electron-transfer mechanisms.
canonical_examples:
- taxon_id: NCBITaxon:35554
  taxon_label: Geobacter sulfurreducens
  note: "extracellular electron transfer via pili/cytochromes"
  reference: DOI:10.1126/science.1088727
- taxon_id: NCBITaxon:70863
  taxon_label: Shewanella oneidensis
  note: "extracellular electron transfer to metals"
  reference: PMID:12368813
causal_graphs:
- graph_id: electron_transfer_redox_carriers
  title: Electron transfer redox carrier mechanism
  description: DOI-backed graph for electron donor/acceptor chemistry, redox proteins,
    membrane electron transport, and extracellular electron-transfer structures.
  nodes:
  - node_id: electron_transfer_trait
    label: Electron transfer
    node_type: TRAIT
    grounding: METPO:1000805
    description: Metabolic electron movement from donor to acceptor.
  - node_id: electron_donor
    label: electron donor
    node_type: CHEMICAL
    description: Reduced substrate or carrier supplying electrons.
    grounding: CHEBI:15022
  - node_id: electron_acceptor
    label: electron acceptor
    node_type: CHEMICAL
    description: Oxidized substrate or carrier receiving electrons.
  - node_id: redox_protein
    label: redox protein
    node_type: GENE_OR_PROTEIN
    description: Protein carrier mediating electron transfer.
    grounding: UniProtKB:A0A076EJF0
  - node_id: cytochrome
    label: c-type cytochrome
    node_type: GENE_OR_PROTEIN
    description: Heme-containing electron-transfer protein.
    grounding: UniProtKB:A0A072TMC1
  - node_id: membrane_electron_transport_chain
    label: membrane electron transport chain
    node_type: PATHWAY
    description: Ordered redox chain in a biological membrane.
    grounding: GO:0022900
  - node_id: extracellular_electron_transfer
    label: extracellular electron transfer
    node_type: BIOLOGICAL_PROCESS
    description: Electron exchange between cells and extracellular minerals, electrodes,
      or cells.
  - node_id: microbial_nanowire
    label: microbial nanowire
    node_type: CELLULAR_LOCALIZATION
    description: Conductive extracellular structure implicated in long-range electron
      transfer.
  - node_id: terminal_acceptor_reduction
    label: terminal acceptor reduction
    node_type: MOLECULAR_FUNCTION
    description: Reduction of the final electron acceptor.
  - node_id: complex_i
    label: NADH dehydrogenase (Complex I)
    node_type: GENE_OR_PROTEIN
    description: Proton-translocating NADH:ubiquinone oxidoreductase entry point of
      the respiratory chain.
  - node_id: ubiquinone
    label: ubiquinone
    node_type: CHEMICAL
    description: Membrane quinone electron carrier reduced to ubiquinol in the respiratory
      chain.
  - node_id: ubiquinol
    label: ubiquinol
    node_type: CHEMICAL
    description: Reduced form of ubiquinone that donates electrons to the cytochrome
      bc1 complex.
    grounding: CHEBI:17976
  - node_id: cytochrome_bc1
    label: cytochrome bc1 complex
    node_type: GENE_OR_PROTEIN
    description: Ubiquinol:cytochrome c oxidoreductase (Complex III) of the respiratory
      chain.
  - node_id: cytochrome_c
    label: cytochrome c
    node_type: GENE_OR_PROTEIN
    description: Mobile electron carrier shuttling electrons from bc1 to the terminal
      oxidase.
    grounding: UniProtKB:A0A061JR98
  - node_id: terminal_oxidase
    label: terminal oxidase
    node_type: GENE_OR_PROTEIN
    description: Terminal respiratory oxidase (Complex IV) that reduces the final
      acceptor.
    grounding: UniProtKB:A0A2U9ILE5
  - node_id: oxygen
    label: oxygen
    node_type: CHEMICAL
    description: Molecular oxygen, terminal electron acceptor in aerobic respiration.
  - node_id: proton_motive_force
    label: proton motive force
    node_type: BIOLOGICAL_PROCESS
    description: Transmembrane electrochemical proton gradient generated by respiratory
      electron transfer.
  edges:
  - subject: electron_transfer_trait
    predicate: transfers electrons from
    object: electron_donor
    description: Electron transfer starts from an electron donor.
    evidence:
    - reference: DOI:10.1016/j.bbabio.2008.09.008
      snippet: free energy of a redox reaction
      notes: Supports donor-side redox chemistry.
  - subject: electron_donor
    predicate: transfers electrons to
    object: electron_acceptor
    description: Electron transfer moves reducing equivalents from donor to acceptor.
    evidence:
    - reference: DOI:10.1016/j.bbabio.2008.09.008
      snippet: electron transfer process
      notes: Supports donor-to-acceptor electron flow.
    predicate_id: METPO:2007403
  - subject: redox_protein
    predicate: mediates transfer between
    object: electron_donor
    description: Redox proteins mediate biological electron-transfer steps.
    evidence:
    - reference: DOI:10.1038/nrmicro.2016.93
      snippet: molecular mechanisms ... exchange electrons
      notes: Supports protein-mediated microbial electron exchange.
  - subject: cytochrome
    predicate: example of
    object: redox_protein
    description: c-type cytochromes are electron-transfer proteins.
    evidence:
    - reference: DOI:10.1038/nrmicro.2016.93
      snippet: c-type cytochromes
      notes: Supports c-type cytochromes as electron-transfer components.
    predicate_id: rdfs:subClassOf
  - subject: membrane_electron_transport_chain
    predicate: performs
    object: terminal_acceptor_reduction
    description: Electron transport chains deliver electrons to terminal acceptors.
    evidence:
    - reference: DOI:10.1016/j.bbabio.2008.09.008
      snippet: membrane-bound electron transport chain
      notes: Supports membrane redox chains as electron-transfer machinery.
  - subject: extracellular_electron_transfer
    predicate: uses structure
    object: microbial_nanowire
    description: Some microbes use conductive appendages or nanowires for extracellular
      electron transfer.
    evidence:
    - reference: DOI:10.1038/nrmicro.2016.93
      snippet: microbial nanowires
      notes: Supports nanowires as an extracellular electron-transfer mechanism.
  - subject: extracellular_electron_transfer
    predicate: uses protein
    object: cytochrome
    description: Extracellular electron transfer can use c-type cytochromes.
    evidence:
    - reference: DOI:10.1038/nrmicro.2016.93
      snippet: c-Type cytochromes
      notes: Supports c-type cytochromes in extracellular electron exchange.
  - subject: complex_i
    predicate: reduces
    object: ubiquinone
    description: Complex I oxidizes NADH and reduces ubiquinone in the respiratory
      chain.
    evidence:
    - reference: DOI:10.3390/ijms252413421
      notes: Complex I oxidizes NADH using ubiquinone (broad bacterial respiratory
        ETC).
    predicate_id: METPO:2000017
  - subject: complex_i
    predicate: translocates
    object: proton_motive_force
    description: Complex I couples NADH:ubiquinone oxidoreduction to transmembrane
      proton translocation, generating the PMF.
    evidence:
    - reference: DOI:10.3390/ijms252413421
      notes: Coupling of redox reaction to vectorial translocation of four protons
        to generate proton motive force.
  - subject: ubiquinol
    predicate: donates electrons to
    object: cytochrome_bc1
    description: Ubiquinol delivers electrons from the quinone pool to the cytochrome
      bc1 complex.
    evidence:
    - reference: DOI:10.1073/pnas.2307093120
      notes: UQH2:cyt c oxidoreductase (Complex III); electrons flow from quinone
        pool to the bc1 complex.
    predicate_id: METPO:2007403
  - subject: cytochrome_bc1
    predicate: transfers electrons to
    object: cytochrome_c
    description: The bc1 complex passes electrons onward to mobile cytochrome c.
    evidence:
    - reference: DOI:10.1073/pnas.2307093120
      notes: Electrons flow to the bc1 complex and onward via cytochrome c.
    predicate_id: METPO:2007403
  - subject: cytochrome_c
    predicate: transfers electrons to
    object: terminal_oxidase
    description: Cytochrome c delivers electrons to the terminal oxidase (Complex
      IV).
    evidence:
    - reference: DOI:10.1073/pnas.2307093120
      notes: Onward via cytochrome c to terminal oxidases (Complex IV) that reduce
        O2 to H2O.
    predicate_id: METPO:2007403
  - subject: terminal_oxidase
    predicate: reduces
    object: oxygen
    description: The terminal oxidase reduces molecular oxygen to water in aerobic
      respiration.
    evidence:
    - reference: DOI:10.1073/pnas.2307093120
      notes: Terminal oxidases (Complex IV) reduce O2 to H2O (broad aerobic respiration
        edge).
    predicate_id: METPO:2000017
curation_history:
- timestamp: '2026-05-05T01:35:46.913647+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-08T00:00:00-07:00'
  curator: codex
  action: ADDED_CAUSAL_GRAPH
  changes: Added DOI-backed causal graph for donor-to-acceptor electron transfer,
    redox proteins, cytochromes, membrane chains, and extracellular nanowire-associated
    transfer.
  llm_assisted: true
- timestamp: '2026-05-23T08:21:49Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (rdfs:subClassOf×1).
  llm_assisted: true
- timestamp: '2026-05-23T21:30:06Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2007403×1).
  llm_assisted: true
- timestamp: '2026-05-24T05:05:14Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (UniProtKB:A0A076EJF0×1, UniProtKB:A0A072TMC1×1).
  llm_assisted: true
- timestamp: '2026-05-24T08:14:32Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:17499×1, GO:0022900×1).
  llm_assisted: true
- timestamp: '2026-06-15T07:19:08Z'
  curator: claude
  action: FIX_NODE_GROUNDING_CURIE
  changes: Overwrote 1 causal-node grounding(s) to corrected CURIEs (phase-2 id-label
    fix; verified vs OAK).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 6 evidence-backed generic edges (8 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:12Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 5 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2007403×3, METPO:2000017×2).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:32Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:17976×1).
  llm_assisted: true
- timestamp: '2026-06-26T07:15:18Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (UniProtKB:A0A061JR98×1, UniProtKB:A0A2U9ILE5×1).
  llm_assisted: true