identifier: METPO:1000479
label: NaCl delta low
definition: A NaCl delta phenotype with a narrow growth-supporting NaCl breadth of
  at most approximately 1% (w/v), characteristic of stenohaline organisms.
definition_source: DOI:10.1093/femsre/fuy009
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000335
synonyms:
- synonym_text: Nad_<=1
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
evidence:
- reference: DOI:10.1093/femsre/fuy009
  snippet: salinity range
  notes: Osmoadaptation review supports narrow salinity-tolerance breadths as the
    stenohaline phenotype, contrasted with euryhaline organisms.
causal_graphs:
- graph_id: nacl_delta_low_stenohaline
  title: NaCl-delta-low stenohaline breadth
  description: DOI-backed graph linking limited osmoadaptive flexibility to a narrow
    NaCl growth breadth (≤ ~1% w/v).
  nodes:
  - node_id: nacl_delta_low_trait
    label: NaCl delta low
    node_type: TRAIT
    grounding: METPO:1000479
    description: NaCl growth-supporting breadth ≤ ~1% w/v.
  - node_id: nacl_delta
    label: NaCl delta
    node_type: TRAIT
    grounding: METPO:1000335
    description: Breadth of the growth-supporting NaCl range.
  - node_id: limited_osmoadaptive_flexibility
    label: limited osmoadaptive flexibility
    node_type: BIOLOGICAL_PROCESS
    description: Narrow capacity to remodel osmolyte pools and ion transport across
      ambient salinities.
  - node_id: ectoine_biosynthesis
    label: ectoine biosynthesis capacity
    node_type: BIOLOGICAL_PROCESS
    description: Capacity to synthesize ectoine as a major compatible solute under
      salt stress.
  - node_id: compatible_solute_transporters
    label: compatible-solute transporters (Opu/ProU)
    node_type: GENE_OR_PROTEIN
    description: Opu/ProU-family uptake systems importing compatible solutes during
      osmoadaptation.
  - node_id: trkh_k_uptake
    label: TrkH potassium uptake system
    node_type: GENE_OR_PROTEIN
    description: TrkH-type K+ uptake transporter supporting intracellular potassium
      homeostasis under salt stress.
  - node_id: nhac_antiporter
    label: NhaC-family Na+/H+ antiporter
    node_type: GENE_OR_PROTEIN
    description: NhaC-family Na+/H+ antiporters mediating ion homeostasis under salt
      stress.
  - node_id: intracellular_proline
    label: intracellular proline accumulation
    node_type: CHEMICAL
    description: Accumulation of proline as a compatible solute supporting growth
      at higher NaCl.
  - node_id: salt_tolerance_breadth
    label: salt-tolerance breadth
    node_type: CAPACITY
    description: Capacity to grow across a range of ambient NaCl concentrations.
  edges:
  - subject: limited_osmoadaptive_flexibility
    predicate: produces
    object: nacl_delta_low_trait
    description: Limited osmoadaptive flexibility yields a narrow NaCl-delta breadth.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: salinity range
      notes: Supports limited osmoadaptive flexibility as the basis of stenohaline
        breadth.
    predicate_id: METPO:2000202
  - subject: nacl_delta_low_trait
    predicate: is a
    object: nacl_delta
    description: NaCl delta low is a quantitative bin of the NaCl-delta phenotype.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: salinity range
      notes: Supports a narrow breadth as a value within the NaCl-delta distribution.
    predicate_id: rdfs:subClassOf
  - subject: ectoine_biosynthesis
    predicate: supports
    object: salt_tolerance_breadth
    description: Ectoine biosynthesis capacity broadens NaCl tolerance; its loss narrows
      the growth range.
    evidence:
    - reference: DOI:10.1128/aem.01905-23
      notes: Wild-type H. elongata synthesizes ectoine as a major osmolyte, whereas
        ectoine-deficient strains become salt sensitive; supports general role of
        ectoine pathway in broadening NaCl tolerance.
  - subject: compatible_solute_transporters
    predicate: supports
    object: limited_osmoadaptive_flexibility
    description: Salinity-induced Opu/ProU compatible-solute transporters underlie
      osmoadaptive flexibility; limited capacity contributes to narrow breadth.
    evidence:
    - reference: DOI:10.1128/aem.00145-24
      notes: Proteomics showed salinity-linked increases in compatible-solute transporters
        (opuAC, proX/proV/proW) supporting osmoadaptation.
  - subject: trkh_k_uptake
    predicate: supports
    object: salt_tolerance_breadth
    description: TrkH K+ uptake supports intracellular K+ homeostasis enabling salt
      tolerance; its absence may contribute to narrow breadth.
    evidence:
    - reference: DOI:10.1128/aem.00145-24
      notes: TrkH listed among salinity-responsive proteins; simultaneous accumulation
        of compatible solutes and K+ supports salt adaptation.
  - subject: nhac_antiporter
    predicate: supports
    object: salt_tolerance_breadth
    description: NhaC Na+/H+ antiporters support ion homeostasis under salt stress;
      a candidate breadth-expanding mechanism whose absence may contribute to NaCl
      delta low.
    evidence:
    - reference: DOI:10.1128/aem.00145-24
      notes: Proteomics show strong salinity-linked increases for NhaC-family antiporters
        (~3.27 and 3.22-fold).
  - subject: intracellular_proline
    predicate: supports
    object: salt_tolerance_breadth
    description: Increased intracellular proline as a compatible solute supports growth
      at higher NaCl, broadening tolerance.
    evidence:
    - reference: DOI:10.1128/aem.01195-24
      notes: Engineered proline biosynthesis with blocked catabolism increased intracellular
        proline and restored growth at 8% NaCl; supports osmolyte role of proline
        in salt-tolerance breadth.
  - subject: salt_tolerance_breadth
    predicate: is a
    object: nacl_delta
    description: Salt-tolerance breadth is the capacity quantified by the NaCl-delta
      phenotype.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      notes: Osmoadaptation review frames salinity tolerance breadth as the basis
        of the NaCl-delta (stenohaline vs euryhaline) distinction.
    predicate_id: rdfs:subClassOf
curation_history:
- timestamp: '2026-05-05T01:35:46.840753+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-12T10:00:00-07:00'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added DOI-backed definition and causal graph linking limited osmoadaptive
    flexibility to the stenohaline NaCl-delta bin.
  llm_assisted: true
- timestamp: '2026-05-20T03:35:30Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2000202×1, rdfs:subClassOf×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 6 evidence-backed generic edges (6 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:10Z'
  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