identifier: METPO:1000469
label: NaCl range low
definition: A NaCl range phenotype in which the upper bound of growth-supporting NaCl
  concentration is at or below approximately 1% (w/v), characteristic of non-halophilic
  or halotolerant organisms.
definition_source: DOI:10.1093/femsre/fuy009
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000334
synonyms:
- synonym_text: Halotolerant
  synonym_type: EXACT_SYNONYM
  source: metpo.owl
- synonym_text: Non-halophile
  synonym_type: EXACT_SYNONYM
  source: metpo.owl
- synonym_text: NaR_<=1
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
evidence:
- reference: DOI:10.1093/femsre/fuy009
  snippet: salinity range
  notes: Osmoadaptation review supports growth limited to ≤ ~1% NaCl as the non-halophilic
    / halotolerant range.
causal_graphs:
- graph_id: nacl_range_low_non_halophile
  title: NaCl-range-low non-halophile range
  description: DOI-backed graph linking limited high-salt tolerance to a growth-supporting
    NaCl range capped at ~1% (w/v).
  nodes:
  - node_id: nacl_range_low_trait
    label: NaCl range low
    node_type: TRAIT
    grounding: METPO:1000469
    description: NaCl growth-supporting range with upper bound ≤ ~1% w/v.
  - node_id: nacl_range
    label: NaCl range
    node_type: TRAIT
    grounding: METPO:1000334
    description: Span of NaCl concentrations supporting growth.
  - node_id: limited_high_salt_tolerance
    label: limited high-salt tolerance
    node_type: BIOLOGICAL_PROCESS
    description: Reduced capacity to maintain osmotic balance above ~1% NaCl.
  - node_id: nacl_concentration
    label: NaCl concentration
    node_type: ENVIRONMENTAL_FACTOR
    description: External sodium chloride concentration in the environment.
  - node_id: hyperosmotic_stress
    label: hyperosmotic stress
    node_type: BIOLOGICAL_PROCESS
    description: Cellular stress from elevated external osmolarity (osmotic upshift).
  - node_id: compatible_solute_accumulation
    label: compatible solute accumulation
    node_type: BIOLOGICAL_PROCESS
    description: Synthesis or import of neutral osmolytes to balance cytoplasmic osmolarity.
  - node_id: hypoosmotic_shock
    label: hypoosmotic shock
    node_type: ENVIRONMENTAL_FACTOR
    description: Rapid drop in external osmolarity causing turgor increase.
  - node_id: mechanosensitive_channels
    label: mechanosensitive channels MscL/MscS
    node_type: GENE_OR_PROTEIN
    description: Tension-gated channels (MscL/MscS) that vent solutes to prevent lysis.
  - node_id: c_di_amp
    label: cyclic di-AMP
    node_type: CHEMICAL
    description: Second messenger that regulates potassium and osmolyte transport.
    grounding: CHEBI:71578
  - node_id: opu_solute_importers
    label: OpuA/OpuC compatible-solute importers
    node_type: GENE_OR_PROTEIN
    description: ABC-type transporters that import compatible solutes like glycine
      betaine.
  - node_id: choline_uptake
    label: choline uptake
    node_type: BIOLOGICAL_PROCESS
    description: Import of external choline used as a glycine betaine precursor.
  - node_id: glycine_betaine_synthesis
    label: glycine betaine biosynthesis
    node_type: BIOLOGICAL_PROCESS
    description: Synthesis of the compatible solute glycine betaine.
    grounding: GO:0031456
  edges:
  - subject: limited_high_salt_tolerance
    predicate: produces
    object: nacl_range_low_trait
    description: Limited tolerance to elevated NaCl caps growth at low salt.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: salinity range
      notes: Supports limited high-salt tolerance as the basis of a low NaCl range.
    predicate_id: METPO:2000202
  - subject: nacl_range_low_trait
    predicate: is a
    object: nacl_range
    description: NaCl range low is a quantitative bin of the NaCl-range phenotype.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: salinity range
      notes: Supports low NaCl range as a value within the NaCl-range distribution.
    predicate_id: rdfs:subClassOf
  - subject: nacl_concentration
    predicate: causes
    object: hyperosmotic_stress
    description: Increased external NaCl concentration causes hyperosmotic stress.
    evidence:
    - reference: DOI:10.1093/femsml/uqad020
      notes: Hyperosmotic upshift elicits rapid K+ import as an emergency response;
        general bacterial osmotic-stress edge.
    predicate_id: biolink:causes
  - subject: hyperosmotic_stress
    predicate: induces
    object: compatible_solute_accumulation
    description: Hyperosmotic stress induces accumulation of compatible solutes.
    evidence:
    - reference: DOI:10.1093/femsml/uqad020
      notes: After K+ import, cells synthesize or import compatible solutes and export
        K+ to reduce cytoplasmic ionic strength.
  - subject: hypoosmotic_shock
    predicate: opens
    object: mechanosensitive_channels
    description: Hypoosmotic shock opens mechanosensitive channels MscL/MscS to prevent
      rupture.
    evidence:
    - reference: DOI:10.1093/femsml/uqad020
      notes: Hypoosmotic shock triggers transient opening of mechanosensitive channels
        (MscL/MscS) to prevent turgor-driven cell rupture; broad across bacteria.
  - subject: c_di_amp
    predicate: inhibits
    object: opu_solute_importers
    description: c-di-AMP binds and inhibits OpuA/OpuC compatible-solute importers.
    evidence:
    - reference: DOI:10.1128/mmbr.00181-23
      notes: c-di-AMP binds CBS-containing importers (OpuA/OpuC) and negatively regulates
        their transport activity.
    predicate_id: RO:0002212
  - subject: choline_uptake
    predicate: enables
    object: glycine_betaine_synthesis
    description: Choline uptake enables synthesis of glycine betaine, a key compatible
      solute.
    evidence:
    - reference: DOI:10.1126/sciadv.ado6229
      notes: BetT mediates uptake of external choline used to synthesize glycine betaine,
        a key compatible solute in hyperosmotic environments.
    predicate_id: RO:0002327
curation_history:
- timestamp: '2026-05-05T01:35:46.835809+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 high-salt
    tolerance to the non-halophile NaCl-range 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 5 evidence-backed generic edges (9 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:10Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (biolink:causes×1, RO:0002212×1, RO:0002327×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:31Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:71578×1, GO:0031456×1).
  llm_assisted: true