identifier: METPO:1000720
label: facultative psychrophilic
definition: A temperature preference characterized by the ability to grow at low temperatures
  (typically below 20 degrees C) while maintaining optimal growth at moderate temperatures.
definition_source: DOI:10.1111/j.1574-6941.2009.00727.x
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000613
synonyms:
- synonym_text: facultative psychrophile
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
created_by: Anthea Guo
evidence:
- reference: DOI:10.1111/j.1574-6941.2009.00727.x
  snippet: optimum temperatures >20 °C and are capable of growth around 0 °C
  notes: Supports facultative psychrophiles as cold-growing organisms with higher
    temperature optima.
causal_graphs:
- graph_id: facultative_psychrophilic_cold_tolerance
  title: Facultative psychrophily cold-tolerance mechanism
  description: Evidence-backed causal sketch linking facultative psychrophily to low-temperature
    growth, moderate-temperature optima, membrane remodeling, and cold acclimation
    proteins.
  nodes:
  - node_id: facultative_psychrophilic_trait
    label: facultative psychrophilic
    node_type: TRAIT
    grounding: METPO:1000720
    description: Capacity to grow at low temperatures while retaining optimal growth
      at moderate temperatures.
  - node_id: low_temperature
    label: low temperature
    node_type: ENVIRONMENTAL_FACTOR
    description: Cold growth condition near 0 degrees C.
    grounding: PATO:0001306
  - node_id: moderate_temperature
    label: moderate temperature
    node_type: ENVIRONMENTAL_FACTOR
    description: Temperature range where facultative psychrophiles can show optimal
      growth.
  - node_id: membrane_fluidity
    label: membrane fluidity
    node_type: QUALITY
    description: Physical state of the membrane needed for transport and growth.
    grounding: METPO:1007505
  - node_id: unsaturated_fatty_acids
    label: unsaturated and branched-chain fatty acids
    node_type: CHEMICAL
    description: Membrane lipid features that maintain fluidity under cold conditions.
  - node_id: cold_shock_proteins
    label: cold-shock proteins
    node_type: GENE_OR_PROTEIN
    description: Proteins involved in cold shock and cold acclimation responses.
  - node_id: two_component_system
    label: two-component signaling system
    node_type: BIOLOGICAL_PROCESS
    description: Signal transduction module activated by membrane-state changes during
      cold sensing.
  - node_id: fatty_acid_desaturase
    label: fatty acid desaturase
    node_type: GENE_OR_PROTEIN
    description: Enzyme introducing double bonds into membrane acyl chains, increasing
      unsaturation in cold.
    grounding: UniProtKB:A0A031GJU0
  - node_id: exopolysaccharides
    label: extracellular polymeric substances (EPS)
    node_type: CHEMICAL
    description: Secreted polysaccharide matrix acting as cryoprotectant.
  - node_id: freeze_thaw_cycles
    label: freeze-thaw cycles
    node_type: ENVIRONMENTAL_FACTOR
    description: Repeated freezing and thawing damaging cells in cold environments.
  - node_id: trehalose
    label: trehalose
    node_type: CHEMICAL
    description: Compatible solute and cryoprotectant protecting cells against abiotic
      stress including cold.
  - node_id: rna_secondary_structure
    label: RNA secondary structure
    node_type: CHEMICAL
    description: Stabilized RNA folds at low temperature that impede transcription
      and translation.
  - node_id: compatible_solutes
    label: compatible osmolytes
    node_type: CHEMICAL
    description: Organic osmolytes (glycine betaine, trehalose, glycerol, sucrose,
      mannitol) preventing cell shrinkage and water loss.
    grounding: CHEBI:23366
  edges:
  - subject: low_temperature
    predicate: is tolerated by
    object: facultative_psychrophilic_trait
    description: Facultative psychrophiles can grow at low temperature.
    evidence:
    - reference: DOI:10.1111/j.1574-6941.2009.00727.x
      snippet: capable of growth around 0 °C
      notes: Review introduction supports low-temperature growth capacity.
  - subject: moderate_temperature
    predicate: supports optimum of
    object: facultative_psychrophilic_trait
    description: Facultative psychrophiles retain optimal growth at moderate temperatures.
    evidence:
    - reference: DOI:10.1111/j.1574-6941.2009.00727.x
      snippet: optimum temperatures >20 °C
      notes: Supports distinction from obligate psychrophiles.
  - subject: low_temperature
    predicate: decreases
    object: membrane_fluidity
    description: Cold temperature decreases membrane fluidity.
    evidence:
    - reference: DOI:10.1038/sj.embor.7400662
      snippet: decreased membrane fluidity
      notes: Supports membrane rigidification as a cold challenge.
    predicate_id: RO:0002212
  - subject: unsaturated_fatty_acids
    predicate: regulates
    object: membrane_fluidity
    description: Lipid remodeling maintains membrane function during cold growth.
    evidence:
    - reference: DOI:10.1146/annurev-micro-091313-103612
      snippet: incorporation of proportionally more unsaturated fatty acids
      notes: Supports homoviscous adaptation during lower-temperature growth.
    predicate_id: RO:0002211
  - subject: cold_shock_proteins
    predicate: contributes to
    object: facultative_psychrophilic_trait
    description: Cold-shock proteins contribute to growth after temperature downshift.
    evidence:
    - reference: DOI:10.1038/sj.embor.7400662
      snippet: Cold-shock proteins have also been described
      notes: Supports cold-shock proteins as cold-acclimation components.
    predicate_id: RO:0002326
  - subject: low_temperature
    predicate: induces
    object: two_component_system
    description: Cold sensing via membrane physical-state change activates a two-component
      system.
    evidence:
    - reference: DOI:10.1007/s42770-023-01057-4
      notes: sensing the cold... leading to the activation of a two-component system
        that transduce the signal
  - subject: fatty_acid_desaturase
    predicate: increases
    object: unsaturated_fatty_acids
    description: Desaturase acting on membrane acyl chains rapidly increases unsaturated
      lipids (homeoviscous response).
    evidence:
    - reference: DOI:10.1016/B978-0-12-809633-8.02282-2
      notes: the desaturase acting on the acyl chains of the membrane lipids comes
        into play, thereby increasing the amount of unsaturated lipid
    predicate_id: RO:0002213
  - subject: exopolysaccharides
    predicate: protects against
    object: freeze_thaw_cycles
    description: EPS surrounding cells acts as cryoprotectant against freeze-thaw
      damage.
    evidence:
    - reference: DOI:10.37256/amtt.5220244537
      notes: exopolysaccharides (EPS) surrounding bacterial cells... providing protection
        against freeze-thaw cycles and acting as cryoprotectants
  - subject: trehalose
    predicate: contributes to
    object: facultative_psychrophilic_trait
    description: Trehalose protects bacteria against abiotic stress including low
      temperature.
    evidence:
    - reference: DOI:10.1038/s41598-023-41323-x
      notes: Trehalose... plays an important role in protecting bacteria against a
        range of stresses
    predicate_id: RO:0002326
  - subject: cold_shock_proteins
    predicate: destabilizes
    object: rna_secondary_structure
    description: CSPs act as chaperones destabilizing RNA secondary structures to
      maintain transcription/translation in cold.
    evidence:
    - reference: DOI:10.1007/s42770-023-01057-4
      notes: CSPs function as chaperones that destabilize those secondary structures
        and maintain a single-stranded molecule
  - subject: compatible_solutes
    predicate: contributes to
    object: facultative_psychrophilic_trait
    description: Accumulation of compatible osmolytes prevents cell shrinkage and
      water loss at sub-zero temperatures.
    evidence:
    - reference: DOI:10.3389/fmicb.2023.1197797
      notes: Accumulation of compatible osmolytes (glycine betaine, trehalose, glycerol,
        sucrose, mannitol etc.)... to prevent cell shrinkage and water loss during
        sub-zero temperature
    predicate_id: RO:0002326
curation_history:
- timestamp: '2026-05-05T01:35:46.908340+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-11T00:00:00-07:00'
  curator: codex
  action: CURATED_WITH_LITERATURE
  changes: Reviewed facultative psychrophilic trait, corrected temperature text encoding,
    and added DOI-backed causal graph for low-temperature growth with moderate-temperature
    optimum.
  llm_assisted: true
- timestamp: '2026-05-20T03:35:29Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002326×1).
  llm_assisted: true
- timestamp: '2026-05-24T04:13:18Z'
  curator: claude
  action: RENAME_PREDICATE_LABELS
  changes: 'Renamed 1 causal-edge predicate label(s) to align with existing groundings:
    maintains → regulates ×1.'
  llm_assisted: true
- timestamp: '2026-05-24T04:13:20Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002211×1).
  llm_assisted: true
- timestamp: '2026-05-24T04:37:59Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (PATO:0000383×1).
  llm_assisted: true
- timestamp: '2026-05-24T04:41:03Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (METPO:1007505×1).
  llm_assisted: true
- timestamp: '2026-05-26T02:30:12Z'
  curator: claude
  action: RETYPE_CAUSAL_NODES
  changes: 'Re-typed 1 causal-node node_type field(s) to align with CausalNodeTypeEnum
    semantics: membrane fluidity: BIOLOGICAL_PROCESS → QUALITY ×1.'
  llm_assisted: true
- timestamp: '2026-06-13T21:03:25Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002212×1).
  llm_assisted: true
- timestamp: '2026-06-15T07:19:08Z'
  curator: claude
  action: FIX_NODE_GROUNDING_CURIE
  changes: Overwrote 1 causal-node grounding(s) to corrected CURIEs (phase-2 id-label
    fix; verified vs OAK).
  llm_assisted: true
- timestamp: '2026-06-17T04:09:43Z'
  curator: claude
  action: REMOVE_REDUNDANT_SYNONYM
  changes: Removed 1 synonym(s) whose text duplicated the label (seeder redundancy;
    no information lost).
  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: '2026-06-24T17:21:09Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002326×2, RO:0002213×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:30Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:23366×1).
  llm_assisted: true
- timestamp: '2026-06-26T07:15:17Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (UniProtKB:A0A031GJU0×1).
  llm_assisted: true