identifier: METPO:1000465 label: NaCl optimum low definition: A NaCl optimum phenotype with the best-growth NaCl concentration at or below approximately 1% (w/v), corresponding to non-halophilic or halotolerant physiology. definition_source: DOI:10.1093/femsre/fuy009 trait_category: ENVIRONMENT term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000333 synonyms: - synonym_text: Halotolerant synonym_type: EXACT_SYNONYM source: metpo.owl - synonym_text: Non-halophile synonym_type: EXACT_SYNONYM source: metpo.owl - synonym_text: NaO_<=1 synonym_type: RELATED_SYNONYM source: metpo.owl evidence: - reference: DOI:10.1093/femsre/fuy009 snippet: optimal NaCl notes: Osmoadaptation review supports low-salt optima as the non-halophilic / halotolerant end of the halophily axis. causal_graphs: - graph_id: nacl_optimum_low_non_halophile_setpoint title: NaCl-optimum-low non-halophile setpoint description: DOI-backed graph linking minimal osmoadaptive load at low ambient NaCl to a low NaCl-optimum (≤1% w/v) consistent with non-halophilic or halotolerant physiology. nodes: - node_id: nacl_optimum_low_trait label: NaCl optimum low node_type: TRAIT grounding: METPO:1000465 description: NaCl optimum at or below ~1% w/v. - node_id: nacl_optimum label: NaCl optimum node_type: TRAIT grounding: METPO:1000333 description: NaCl concentration supporting maximal growth. - node_id: low_ambient_nacl label: low ambient NaCl node_type: ENVIRONMENTAL_FACTOR description: Freshwater-like or mildly saline external NaCl ≤ ~1% w/v. - node_id: minimal_osmoadaptive_load label: minimal osmoadaptive load node_type: BIOLOGICAL_PROCESS description: Low demand on osmolyte and ion-transport machinery at low salt. - node_id: non_halophile_optimum_definition label: non-halophilic optimum NaCl (<0.2 M / ~1% w/v) node_type: TRAIT description: Optimal growth at less than 0.2 M (about 1% w/v) NaCl, defining non-halophilic physiology. - node_id: halotolerant_organism label: halotolerant organism node_type: TRAIT description: A non-halophilic organism able to grow at high salt concentrations. - node_id: compatible_solute_accumulation label: compatible solute accumulation node_type: BIOLOGICAL_PROCESS description: Intracellular accumulation of low-molecular-weight compatible solutes (osmolytes) in response to osmotic stress. - node_id: osmotic_stress_adaptation label: osmotic stress adaptation node_type: BIOLOGICAL_PROCESS description: Cellular adaptation maintaining turgor and function under osmotic stress. - node_id: cyclic_di_amp label: cyclic di-AMP node_type: CHEMICAL description: Second messenger nucleotide that regulates osmolyte and ion transport. grounding: CHEBI:71578 - node_id: k_uptake_systems label: K+ uptake systems (Trk/Ktr/Kup/KimA) node_type: GENE_OR_PROTEIN description: Potassium uptake transporters whose activity responds to osmotic signaling. - node_id: opua_opuc_transport label: OpuA/OpuC compatible-solute transporters node_type: GENE_OR_PROTEIN description: ABC-type importers of compatible solutes such as glycine betaine. edges: - subject: low_ambient_nacl predicate: imposes object: minimal_osmoadaptive_load description: Low ambient NaCl imposes minimal osmoadaptive demand on the cell. evidence: - reference: DOI:10.1093/femsre/fuy009 snippet: optimal NaCl notes: Supports low-salt environments as the context for non-halophilic optima. - subject: minimal_osmoadaptive_load predicate: produces object: nacl_optimum_low_trait description: Minimal osmoadaptive demand yields a low NaCl-optimum setpoint. evidence: - reference: DOI:10.1093/femsre/fuy009 snippet: optimal NaCl notes: Supports low-salt optima as the non-halophile / halotolerant outcome. predicate_id: METPO:2000202 - subject: nacl_optimum_low_trait predicate: is a object: nacl_optimum description: NaCl optimum low is a quantitative bin of the NaCl-optimum phenotype. evidence: - reference: DOI:10.1093/femsre/fuy009 snippet: optimal NaCl notes: Supports low-salt optima as a value within the NaCl-optimum distribution. predicate_id: rdfs:subClassOf - subject: non_halophile_optimum_definition predicate: defined as object: nacl_optimum_low_trait description: Non-halophilic optimum at <0.2 M (~1% w/v) NaCl corresponds to the NaCl-optimum-low trait. evidence: - reference: DOI:10.3389/fmicb.2019.01895 notes: non-halophilic microorganisms grow optimally at less than 0.2 M (1%) NaCl. - subject: halotolerant_organism predicate: is a object: non_halophile_optimum_definition description: Halotolerant organisms are non-halophiles (low-NaCl optimum) able to grow at high salt. evidence: - reference: DOI:10.1007/s40201-020-00519-3 notes: halotolerant organisms are those non-halophilic able to grow at high salt concentrations. predicate_id: rdfs:subClassOf - subject: compatible_solute_accumulation predicate: supports object: osmotic_stress_adaptation description: Accumulation of compatible solutes supports adaptation to osmotic stress. evidence: - reference: DOI:10.1128/aem.00619-25 notes: Bacteria respond to osmotic stress by intracellularly accumulating compatible solutes. - subject: minimal_osmoadaptive_load predicate: reduces demand for object: compatible_solute_accumulation description: At low ambient NaCl, minimal osmoadaptive load reduces the need for compatible-solute accumulation. evidence: - reference: DOI:10.1128/aem.00619-25 notes: Compatible solutes are accumulated in response to osmotic stress; low salt imposes minimal such demand. - subject: cyclic_di_amp predicate: inhibits object: k_uptake_systems description: Cyclic di-AMP binds gating subunits of Trk/Ktr/Kup/KimA and inhibits K+ uptake. evidence: - reference: DOI:10.1128/mmbr.00181-23 notes: gating subunits of Trk/Ktr bind cyclic di-AMP; KUP-family activity is inhibited by cyclic di-AMP. predicate_id: RO:0002212 - subject: cyclic_di_amp predicate: negatively regulates object: opua_opuc_transport description: Cyclic di-AMP binds OpuA/OpuC importers and negatively regulates compatible-solute transport. evidence: - reference: DOI:10.1128/mmbr.00181-23 notes: c-di-AMP binds CBS and RCK_C domains of OpuA/OpuC and negatively regulates their transport activity. curation_history: - timestamp: '2026-05-05T01:35:46.833539+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 minimal osmoadaptive load at low ambient NaCl to the non-halophile / halotolerant NaCl-optimum 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 (7 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:10Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (rdfs:subClassOf×1, RO:0002212×1). llm_assisted: true - timestamp: '2026-06-24T17:23:31Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:71578×1). llm_assisted: true