identifier: METPO:1000802
label: Anaerobic respiration
definition: A respiration in which an organism uses electron acceptors other than
  oxygen for energy production.
definition_source: DOI:10.1128/mmbr.61.4.533-616.1997
trait_category: METABOLISM
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000800
synonyms:
- synonym_text: Anoxic respiration
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
- synonym_text: Dissimilatory respiration (non-O₂)
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
evidence:
- reference: DOI:10.1128/mmbr.61.4.533-616.1997
  snippet: N oxides as terminal electron acceptors
  notes: Denitrification review supports anaerobic respiration using non-oxygen terminal
    electron acceptors.
canonical_examples:
- taxon_id: NCBITaxon:70863
  taxon_label: Shewanella oneidensis
  note: "respires metals/alternative acceptors"
  reference: PMID:12368813
- taxon_id: NCBITaxon:562
  taxon_label: Escherichia coli
  note: "nitrate/fumarate anaerobic respiration"
  reference: PMID:9230919
causal_graphs:
- graph_id: anaerobic_respiration_denitrification
  title: Anaerobic respiration with nitrogen oxide acceptors
  description: Evidence-backed causal sketch using denitrification as a representative
    anaerobic respiratory process.
  nodes:
  - node_id: anaerobic_respiration_trait
    label: Anaerobic respiration
    node_type: TRAIT
    grounding: METPO:1000802
    description: Respiration using terminal electron acceptors other than oxygen.
  - node_id: low_oxygen_condition
    label: anaerobic or microaerophilic condition
    node_type: ENVIRONMENTAL_FACTOR
    description: Low-oxygen condition permissive for denitrifying respiration.
  - node_id: denitrification
    label: denitrification
    node_type: BIOLOGICAL_PROCESS
    grounding: GO:0019330
    description: Respiratory reduction of nitrogen oxides.
  - node_id: nitrogen_oxides
    label: nitrogen oxides
    node_type: CHEMICAL
    description: Non-oxygen terminal electron acceptors used in denitrification.
    grounding: CHEBI:35196
  - node_id: terminal_electron_acceptor
    label: terminal electron acceptor
    node_type: MOLECULAR_FUNCTION
    description: Electron-accepting role in respiratory bioenergetics.
    grounding: METPO:1007504
  - node_id: energy_conservation
    label: cellular energy conservation
    node_type: BIOLOGICAL_PROCESS
    description: Bioenergetic output of respiratory electron transport.
  - node_id: oxygen_limitation
    label: oxygen limitation / anoxic transition
    node_type: ENVIRONMENTAL_FACTOR
    description: Onset of low-oxygen / anoxic conditions that triggers expression
      and activity of anaerobic respiratory reductases.
  - node_id: denitrification_reductases
    label: denitrification reductases
    node_type: GENE_OR_PROTEIN
    description: Respiratory reductases (e.g., Nar, Nos) that catalyze stepwise reduction
      of nitrogen oxides during denitrification.
  - node_id: nitrate_reductase
    label: respiratory nitrate reductase (NarGHI)
    node_type: GENE_OR_PROTEIN
    description: Membrane-bound respiratory nitrate reductase complex that reduces
      nitrate to nitrite.
  - node_id: nitrate
    label: nitrate
    node_type: CHEMICAL
    description: Oxidized nitrogen oxyanion reduced to nitrite during nitrate respiration.
    grounding: CHEBI:17632
  - node_id: nitrite
    label: nitrite
    node_type: CHEMICAL
    description: Reduced product of nitrate reduction and substrate for subsequent
      denitrification or DNRA.
    grounding: CHEBI:16301
  - node_id: nitrous_oxide_reductase
    label: nitrous oxide reductase (NosZ)
    node_type: GENE_OR_PROTEIN
    description: Terminal reductase of denitrification reducing nitrous oxide to dinitrogen.
  - node_id: nitrous_oxide
    label: nitrous oxide
    node_type: CHEMICAL
    description: Denitrification intermediate reduced to dinitrogen by NosZ.
    grounding: CHEBI:17045
  - node_id: dinitrogen
    label: dinitrogen
    node_type: CHEMICAL
    description: Gaseous end product of complete denitrification.
    grounding: CHEBI:17997
  edges:
  - subject: denitrification
    predicate: occurs in
    object: low_oxygen_condition
    description: Denitrification can occur under anaerobic and microaerophilic conditions.
    evidence:
    - reference: DOI:10.1128/mmbr.61.4.533-616.1997
      snippet: under anaerobic, microaerophilic, and occasionally aerobic conditions
      notes: Supports low-oxygen context for denitrification.
    predicate_id: biolink:occurs_in
  - subject: nitrogen_oxides
    predicate: acts as
    object: terminal_electron_acceptor
    description: Nitrogen oxides serve as terminal electron acceptors.
    evidence:
    - reference: DOI:10.1128/mmbr.61.4.533-616.1997
      snippet: N oxides as terminal electron acceptors
      notes: Supports the terminal electron acceptor role.
  - subject: denitrification
    predicate: uses
    object: nitrogen_oxides
    description: Denitrification uses nitrogen oxides in respiratory bioenergetics.
    evidence:
    - reference: DOI:10.1128/mmbr.61.4.533-616.1997
      snippet: making use of N oxides
      notes: Supports nitrogen oxides as denitrification substrates.
  - subject: denitrification
    predicate: conserves
    object: energy_conservation
    description: Denitrification is a respiratory route for energy conservation.
    evidence:
    - reference: DOI:10.1128/mmbr.61.4.533-616.1997
      snippet: distinct means of energy conservation
      notes: Supports energy conservation via denitrification.
  - subject: anaerobic_respiration_trait
    predicate: exemplified by
    object: denitrification
    description: Denitrification is a representative anaerobic respiratory process.
    evidence:
    - reference: DOI:10.1128/mmbr.61.4.533-616.1997
      snippet: terminal electron acceptors for cellular bioenergetics
      notes: Supports denitrification as non-oxygen respiratory bioenergetics.
  - subject: oxygen_limitation
    predicate: increases activity of
    object: denitrification_reductases
    description: Onset of anoxia drives early transcription and activity of denitrification
      reductases.
    evidence:
    - reference: DOI:10.1038/s41467-024-51688-w
      notes: early transcription of NAR (and sometimes NOS) at the cusp of anoxia;
        environmental driver activating denitrification reductases.
  - subject: nitrate_reductase
    predicate: catalyzes reduction of
    object: nitrate
    description: Respiratory nitrate reductase NarGHI catalyzes the reduction of nitrate
      to nitrite.
    evidence:
    - reference: DOI:10.1128/msystems.00967-23
      notes: the narGHI nitrate reductase cluster; NarGHI catalyzes nitrate reduction
        to nitrite, the canonical first step of nitrate respiration.
  - subject: nitrate_reductase
    predicate: produces
    object: nitrite
    description: Reduction of nitrate by NarGHI yields nitrite.
    evidence:
    - reference: DOI:10.1128/msystems.00967-23
      notes: NarGHI nitrate reductase produces nitrite from nitrate.
    predicate_id: METPO:2000202
  - subject: nitrous_oxide_reductase
    predicate: reduces
    object: nitrous_oxide
    description: NosZ reduces nitrous oxide to dinitrogen, the terminal step of complete
      denitrification.
    evidence:
    - reference: DOI:10.1128/msystems.00967-23
      notes: NosZ reduces N2O to N2; canonical terminal denitrification step.
    predicate_id: METPO:2000017
  - subject: nitrous_oxide_reductase
    predicate: produces
    object: dinitrogen
    description: NosZ-catalyzed reduction of nitrous oxide produces dinitrogen.
    evidence:
    - reference: DOI:10.1128/msystems.00967-23
      notes: NosZ reduces N2O to N2; produces dinitrogen as denitrification end product.
    predicate_id: METPO:2000202
curation_history:
- timestamp: '2026-05-05T01:35:46.912036+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-07T00:00:00-07:00'
  curator: codex
  action: ADDED_CAUSAL_GRAPH
  changes: Added DOI-backed causal graph for anaerobic respiration using denitrification
    and nitrogen oxide terminal electron acceptors.
  llm_assisted: true
- timestamp: '2026-05-24T04:41:03Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (METPO:1007504×1).
  llm_assisted: true
- timestamp: '2026-05-26T05:00:47Z'
  curator: claude
  action: RENAME_PREDICATE_LABELS
  changes: 'Renamed 1 causal-edge predicate label(s) to align with existing groundings:
    occurs under → occurs in ×1.'
  llm_assisted: true
- timestamp: '2026-05-26T05:00:50Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (biolink:occurs_in×1).
  llm_assisted: true
- timestamp: '2026-06-14T05:51:45Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:35196×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 5 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 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2000202×2, METPO:2000017×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:21:18Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:17632×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:32Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 3 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:16301×1, CHEBI:17045×1, CHEBI:17997×1).
  llm_assisted: true