identifier: METPO:1000441 label: temperature optimum very low definition: A temperature optimum phenotype with the best-growth ambient temperature at or below approximately 10 °C, characteristic of psychrophilic physiology. definition_source: DOI:10.1038/sj.embor.7400662 trait_category: ENVIRONMENT term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000304 synonyms: - synonym_text: Psychrophile synonym_type: EXACT_SYNONYM source: metpo.owl - synonym_text: TO_<=10 synonym_type: RELATED_SYNONYM source: metpo.owl evidence: - reference: DOI:10.1038/sj.embor.7400662 snippet: growing well at temperatures around the freezing point of water notes: Psychrophile review supports growth at very low temperatures as the psychrophilic optimum. causal_graphs: - graph_id: temperature_optimum_very_low_psychrophile_setpoint title: Temperature-optimum-very-low psychrophile setpoint description: DOI-backed graph linking cold-adapted membrane and enzyme machinery to a temperature optimum at or below ~10 °C. nodes: - node_id: temperature_optimum_very_low_trait label: temperature optimum very low node_type: TRAIT grounding: METPO:1000441 description: Temperature optimum at or below ~10 °C. - node_id: temperature_optimum label: temperature optimum node_type: TRAIT grounding: METPO:1000304 description: Ambient temperature supporting maximal growth. - node_id: cold_environment label: cold environment node_type: ENVIRONMENTAL_FACTOR description: Habitat ambient temperature near the freezing point of water. grounding: ENVO:01000309 - node_id: psychrophile_machinery label: psychrophile cold-adapted machinery node_type: BIOLOGICAL_PROCESS description: Cold-active enzymes and unsaturated-lipid membranes sustaining function at very low temperature. - node_id: unsaturated_fatty_acids label: unsaturated fatty acids node_type: CHEMICAL description: Unsaturated acyl chains that lower membrane melting point. grounding: CHEBI:27208 - node_id: membrane_fluidity label: membrane fluidity at low temperature node_type: QUALITY description: Maintained membrane fluidity sustaining transport and function in the cold. - node_id: fatty_acid_desaturase label: fatty acid desaturase activity node_type: MOLECULAR_FUNCTION description: Desaturase activity introducing double bonds into fatty acyl chains. - node_id: cold_shock_proteins label: cold shock proteins / RNA chaperones node_type: GENE_OR_PROTEIN description: RNA chaperones that resolve nucleic-acid secondary structure stabilized in the cold. - node_id: translation_low_temperature label: translation at low temperature node_type: BIOLOGICAL_PROCESS description: Maintenance of transcription and translation under low-temperature conditions. - node_id: glycine_betaine label: glycine betaine node_type: CHEMICAL description: Compatible solute stabilizing proteins and membranes under cold stress. grounding: CHEBI:17750 - node_id: protein_membrane_stabilization label: protein and membrane stabilization under cold stress node_type: BIOLOGICAL_PROCESS description: Prevention of protein aggregation and stabilization of membranes during cold stress. - node_id: trehalose label: trehalose node_type: CHEMICAL description: Disaccharide compatible solute acting as a cryoprotectant. - node_id: cryoprotection label: cryoprotection node_type: BIOLOGICAL_PROCESS description: Protection of cellular structures against freezing and freeze-thaw damage. - node_id: antifreeze_proteins label: antifreeze / ice-binding proteins node_type: GENE_OR_PROTEIN description: Ice-binding proteins that depress freezing point via thermal hysteresis. - node_id: thermal_hysteresis label: thermal hysteresis / lowered freezing point node_type: BIOLOGICAL_PROCESS description: Lowering of the freezing point separating melting and freezing temperatures. - node_id: enzyme_structural_flexibility label: increased enzyme structural flexibility node_type: QUALITY description: Greater conformational flexibility of cold-adapted enzymes. - node_id: catalytic_activity_low_temperature label: catalytic activity at low temperature node_type: MOLECULAR_FUNCTION description: Retention of catalytic efficiency at low temperature. edges: - subject: cold_environment predicate: selects for object: psychrophile_machinery description: Cold environments select for cold-adapted enzymes and lipids. evidence: - reference: DOI:10.1038/sj.embor.7400662 snippet: growing well at temperatures around the freezing point of water notes: Supports cold habitats as the context for psychrophile machinery. predicate_id: METPO:2007401 - subject: psychrophile_machinery predicate: produces object: temperature_optimum_very_low_trait description: Psychrophile cold-adapted machinery yields a very-low temperature optimum. evidence: - reference: DOI:10.1146/annurev-micro-091313-103612 snippet: more unsaturated fatty acids notes: Supports homoviscous adaptation as the mechanism setting the psychrophile optimum. predicate_id: METPO:2000202 - subject: temperature_optimum_very_low_trait predicate: is a object: temperature_optimum description: Temperature optimum very low is a quantitative bin of the temperature-optimum phenotype. evidence: - reference: DOI:10.1038/sj.embor.7400662 snippet: growing well at temperatures around the freezing point of water notes: Supports a ≤10 °C optimum as a value within the temperature-optimum distribution. predicate_id: rdfs:subClassOf - subject: fatty_acid_desaturase predicate: increases abundance of object: unsaturated_fatty_acids description: Fatty acid desaturase activity increases unsaturated acyl chains. evidence: - reference: DOI:10.17159/sajs.2018/20170254 notes: activation of desaturases, increased unsaturated acyl chains - subject: unsaturated_fatty_acids predicate: maintains object: membrane_fluidity description: Increased unsaturated fatty acids maintain membrane fluidity at low temperature. evidence: - reference: DOI:10.1128/AEM.01928-22 notes: maintain membrane fluidity by improving the ratio of unsaturated fatty acids - subject: membrane_fluidity predicate: supports object: psychrophile_machinery description: Maintained membrane fluidity supports cold-adapted cellular machinery. evidence: - reference: DOI:10.1128/AEM.01928-22 notes: maintained membrane fluidity sustains function at low temperature - subject: cold_shock_proteins predicate: supports object: translation_low_temperature description: Cold shock proteins / RNA chaperones support transcription and translation in the cold. evidence: - reference: DOI:10.17159/sajs.2018/20170254 notes: Cold-shock proteins are major cold responses, functioning in regulation of transcription/translation - subject: glycine_betaine predicate: stabilizes object: protein_membrane_stabilization description: Glycine betaine prevents protein aggregation and stabilizes membranes during cold stress. evidence: - reference: DOI:10.17159/sajs.2018/20170254 notes: including glycine betaine and trehalose - prevent protein aggregation and stabilize membranes - subject: trehalose predicate: acts as object: cryoprotection description: Trehalose acts as a cryoprotectant. evidence: - reference: DOI:10.1038/sj.embor.7400662 notes: Compatible solutes (trehalose) and extracellular polysaccharides act as cryoprotectants - subject: antifreeze_proteins predicate: causes object: thermal_hysteresis description: Antifreeze proteins lower the freezing point via thermal hysteresis. evidence: - reference: DOI:10.1007/s42770-023-01057-4 notes: AFPs lower freezing point via thermal hysteresis predicate_id: biolink:causes - subject: enzyme_structural_flexibility predicate: increases object: catalytic_activity_low_temperature description: Increased enzyme structural flexibility increases catalytic activity at low temperature. evidence: - reference: DOI:10.17159/sajs.2018/20170254 notes: Cold-adapted enzymes display increased structural flexibility and higher catalytic efficiency predicate_id: RO:0002213 curation_history: - timestamp: '2026-05-05T01:35:46.818713+00:00' curator: seed_from_metpo action: SEEDED_FROM_METPO changes: imported from data/raw/metpo.owl (CLASS) llm_assisted: false - timestamp: '2026-05-13T11:00:00-07:00' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added DOI-backed definition and causal graph linking psychrophile cold-adapted machinery to the temperature-optimum-very-low 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: '2026-05-23T21:30:06Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007401×1). 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 (ENVO:01000309×1). llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 8 evidence-backed generic edges (13 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:11Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:causes×1, RO:0002213×1). llm_assisted: true - timestamp: '2026-06-24T17:23:32Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:27208×1, CHEBI:17750×1). llm_assisted: true