identifier: traitmech:000031 label: dissimilatory iron reduction definition: An anaerobic respiratory metabolism in which an organism conserves energy for growth by coupling the oxidation of organic matter or hydrogen to the reduction of Fe(III) as a terminal electron acceptor. Characteristic of Geobacter and Shewanella, often via extracellular electron transfer. definition_source: DOI:10.1128/mr.55.2.259-287.1991 trait_category: METABOLISM term_kind: CLASS mapping_status: REVIEWED parent_traits: - traitmech:000039 synonyms: - synonym_text: ferric iron respiration synonym_type: RELATED_SYNONYM source: DOI:10.1128/mr.55.2.259-287.1991 - synonym_text: dissimilatory Fe(III) reduction synonym_type: EXACT_SYNONYM source: DOI:10.1128/mr.55.2.259-287.1991 evidence: - reference: DOI:10.1128/mr.55.2.259-287.1991 snippet: The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater notes: Lovley review establishes dissimilatory Fe(III)/Mn(IV) reduction as energy-conserving anaerobic respiration coupling organic-matter oxidation to metal reduction. - reference: PMID:7826009 notes: Nealson & Saffarini, "Iron and manganese in anaerobic respiration", supports Fe(III) and Mn(IV) as terminal electron acceptors competitive with nitrate. canonical_examples: - taxon_id: NCBITaxon:35554 taxon_label: Geobacter sulfurreducens note: "Textbook Fe(III)-reducer; oxidizes acetate coupled to metal reduction (type strain PCA)." reference: https://pmc.ncbi.nlm.nih.gov/articles/PMC201883/ causal_graphs: - graph_id: dir_ferric_iron_respiration title: Dissimilatory iron reduction respires Fe(III) to Fe(II) description: Evidence-backed causal sketch linking ferric iron as terminal electron acceptor to anaerobic respiration in Geobacter and Shewanella. nodes: - node_id: dir_trait label: dissimilatory iron reduction node_type: TRAIT grounding: traitmech:000031 description: Anaerobic respiration on Fe(III) as terminal electron acceptor. - node_id: ferric_iron label: iron(3+) node_type: CHEMICAL grounding: CHEBI:29034 description: Terminal electron acceptor reduced in DIR. - node_id: ferrous_iron label: iron(2+) node_type: CHEMICAL grounding: CHEBI:29033 description: Soluble product released after Fe(III) reduction. - node_id: anaerobic_respiration label: energy-conserving anaerobic respiration node_type: BIOLOGICAL_PROCESS description: Anaerobic respiratory metabolism conserving energy via a terminal electron acceptor. - node_id: organic_matter_oxidation label: oxidation of organic matter node_type: BIOLOGICAL_PROCESS description: Oxidation of organic carbon serving as the electron donor in DIR. - node_id: hydrogen_oxidation label: H2 oxidation node_type: BIOLOGICAL_PROCESS description: Oxidation of molecular hydrogen as an electron donor coupled to Fe(III) reduction. - node_id: dissolved_fe3_om_complex label: dissolved Fe(III)-organic-matter complex node_type: CHEMICAL description: Soluble Fe(III) bound to organic matter; reduced faster than solid Fe(III) minerals. - node_id: solid_fe3_mineral label: solid Fe(III) mineral node_type: CHEMICAL description: Insoluble Fe(III) oxide mineral phase serving as terminal electron acceptor. edges: - subject: ferric_iron predicate: oxidized to object: ferrous_iron description: Fe(III) is reduced to Fe(II) as DIR terminal-acceptor chemistry. evidence: - reference: DOI:10.1128/mr.55.2.259-287.1991 notes: Lovley establishes Fe(III) reduction coupled to organic-matter oxidation as energy-conserving anaerobic respiration. predicate_id: METPO:2007405 - subject: ferric_iron predicate: enables object: dir_trait description: Fe(III) acts as terminal electron acceptor enabling DIR. evidence: - reference: PMID:7826009 notes: Nealson & Saffarini support Fe(III) as a terminal electron acceptor competitive with nitrate. predicate_id: RO:0002327 - subject: dir_trait predicate: is a object: anaerobic_respiration description: DIR is a form of energy-conserving anaerobic respiration. evidence: - reference: DOI:10.1128/mr.55.2.259-287.1991 notes: Organisms can obtain energy by completely oxidizing organic compounds to CO2 with Fe(III) or Mn(IV) as the sole acceptor. predicate_id: rdfs:subClassOf - subject: organic_matter_oxidation predicate: coupled to object: ferric_iron description: Oxidation of organic matter is coupled to Fe(III) reduction in DIR. evidence: - reference: DOI:10.1128/mr.55.2.259-287.1991 notes: The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is the direct result of enzymatic activity of specialized microorganisms. - subject: hydrogen_oxidation predicate: coupled to object: ferric_iron description: H2 oxidation can serve as the electron donor coupled to Fe(III) reduction. evidence: - reference: DOI:10.1128/mr.55.2.259-287.1991 notes: Abundant evidence that H2 oxidation can be coupled to Fe(III)/Mn(IV) reduction in sediments. - subject: dissolved_fe3_om_complex predicate: reduced faster than object: solid_fe3_mineral description: Dissolved Fe(III)-OM complexes are reduced at significantly higher rates than solid Fe(III) minerals. evidence: - reference: DOI:10.1007/s10533-024-01186-4 notes: The reduction rates of dissolved Fe(III)-OM complexes are significantly higher than those observed for solid Fe(III) minerals. curation_history: - timestamp: '2026-05-30T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate METABOLISM trait (dissimilatory iron reduction) from literature research to fill the metal-redox metabolism gap. llm_assisted: true - timestamp: '2026-06-10T14:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (Fe(III) → Fe(II) respiration) with CHEBI node groundings and RO/METPO predicate groundings; promoted PROPOSED to REVIEWED. llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 4 evidence-backed generic edges (5 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:12Z' 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