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dissimilatory nitrate reduction to ammonium

traitmech:000030 · CLASS · REVIEWED

An anaerobic respiratory metabolism in which nitrate is reduced via nitrite to ammonium (rather than to N2), conserving fixed nitrogen within the ecosystem. It is favored over denitrification under nitrate-limited, high-electron-donor conditions.

DNRA reduces nitrate to ammonium, conserving fixed nitrogen

Evidence-backed causal sketch linking nitrate respiration ending in ammonium to nitrogen retention under high donor-to-acceptor ratios.

DNRA reduces nitrate to ammonium, conserving fixed nitrogen Interactive directed graph showing evidence-backed causal relationships for dissimilatory nitrate reduction to ammonium.

Edge evidence

  • nitrate oxidized to ammonium METPO:2007405

    Nitrate is reduced via nitrite to ammonium, retaining N in the cell/system.

    • DOI:10.1126/science.1254070 Kraft et al. show DNRA produces ammonium from nitrate under nitrate-limited conditions.
  • high donor-to-acceptor ratio selects for dissimilatory nitrate reduction to ammonium METPO:2007401

    High donor-to-acceptor ratio favors DNRA over denitrification.

    • DOI:10.1007/s11157-025-09719-5 DNRA review supports its competitive advantage and N-retaining role under nitrate-limited conditions.
  • nitrate reduced to nitrite

    NarGHI nitrate reductase catalyzes the canonical first DNRA step, reducing nitrate to nitrite.

    • DOI:10.1128/msystems.00967-23 Nitrate is reduced via nitrite; known nitrate reductases include cytoplasmic NarGHI (egas2024).
  • NarGHI nitrate reductase catalyzes nitrite biolink:catalyzes

    NarGHI nitrate reductase catalyzes production of nitrite from nitrate.

    • DOI:10.1128/msystems.00967-23 Known nitrate reductases include periplasmic NapAB and cytoplasmic NarGHI catalyzing the first step.
  • nitrite reduced to ammonium

    NrfA cytochrome c nitrite reductase catalyzes the canonical second DNRA step, reducing nitrite to ammonium.

    • DOI:10.1128/aem.00292-25 Second step performed by cytochrome c nitrite reductase (NrfA): reduction of nitrite to ammonium (hird2025).
  • NrfA cytochrome c nitrite reductase catalyzes ammonium biolink:catalyzes

    NrfA reduces nitrite to ammonium, the final DNRA product.

    • DOI:10.1128/aem.00292-25 Cytochrome c nitrite reductase (NrfA) performs the canonical reduction of nitrite to ammonium.
  • NarX-NarL two-component system activates expression of nrf operon

    NarX-NarL nitrate/nitrite sensing activates transcription of the nrf operon.

    • DOI:10.1128/aem.00292-25 Expression of nap and nrf operons is tightly regulated by NarX-NarL and NarQ-NarP, activating transcription under appropriate conditions (hird2025).
  • FNR regulator activates expression of nrf operon

    FNR activates nrf operon transcription under anaerobic conditions.

    • DOI:10.1128/aem.00292-25 FNR (O2/NO sensing) activates transcription under anaerobic and nitrate/nitrite-rich conditions (hird2025).
  • anaerobic conditions permits dissimilatory nitrate reduction to ammonium

    Anaerobic conditions, sensed via FNR, permit DNRA respiration.

    • DOI:10.1128/aem.00292-25 nap/nrf operon expression activated under anaerobic conditions; DNRA proceeds under oxygen-depleted conditions (hird2025).

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.1126/science.1254070

Parent traits (1)

Synonyms (2)

  • DNRA EXACT_SYNONYM · DOI:10.1126/science.1254070
  • nitrate ammonification RELATED_SYNONYM · DOI:10.1007/s11157-025-09719-5

kg-microbe context

Matched 1 kg-microbe node via parent_proxy.

  • METPO:1000802 [-0.426, -1.069, -1.023, +1.207, …]

512-dim DeepWalkSkipGramEnsmallen embedding from kg-microbe (2026-04-25).

Nearest neighbors in embedding space

Top-8 cosine-similar METPO traits from the 2026-04-25 deepwalk (512-D).

Curation history

  1. · PROPOSED_FROM_RESEARCH · claude

    Proposed candidate METABOLISM trait (dissimilatory nitrate reduction to ammonium) from literature research to fill the nitrogen-cycling gap.

  2. · CURATED_CAUSAL_GRAPH · claude

    Added evidence-backed causal graph (DNRA nitrate → ammonium retention) with CHEBI node groundings and METPO predicate groundings; promoted PROPOSED to REVIEWED.

  3. · ENRICH_CAUSAL_GRAPH · claude

    Added 7 evidence-backed generic edges (7 new nodes) from the deep-research report.

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:catalyzes×2).