identifier: METPO:1000618
label: psychrotolerant
definition: A temperature preference in which growth can occur at low temperatures
  without an obligate low-temperature preference.
definition_source: DOI:10.1099/ijs.0.65141-0
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000613
evidence:
- reference: DOI:10.1099/ijs.0.65141-0
  snippet: Pseudomonas guineae sp. nov., a novel psychrotolerant bacterium
  notes: 'Organism example: Pseudomonas guineae is described as psychrotolerant.'
- reference: DOI:10.1038/sj.embor.7400662
  snippet: decreased membrane fluidity
  notes: Psychrophile review supports cold-end membrane stress as the challenge that
    psychrotolerant facultative adaptation overcomes without full psychrophile dedication.
canonical_examples:
- taxon_id: NCBITaxon:1639
  taxon_label: Listeria monocytogenes
  note: "grows at refrigeration temperatures"
  reference: DOI:10.3389/fmicb.2018.02700
- taxon_id: NCBITaxon:294
  taxon_label: Pseudomonas fluorescens
  note: "cold-tolerant"
  reference: PMID:31178851
causal_graphs:
- graph_id: psychrotolerant_facultative_cold_adaptation
  title: Psychrotolerant facultative cold-adaptation mechanism
  description: DOI-backed graph linking psychrotolerance to low-temperature membrane
    and enzyme acclimation that does not preclude growth at moderate ambient temperatures.
  nodes:
  - node_id: psychrotolerant_trait
    label: psychrotolerant
    node_type: TRAIT
    grounding: METPO:1000618
    description: Growth at low temperatures without an obligate low-temperature preference.
  - node_id: low_temperature
    label: low temperature
    node_type: ENVIRONMENTAL_FACTOR
    description: Ambient temperature below the mesophile optimum range.
    grounding: PATO:0001306
  - node_id: membrane_fluidity
    label: membrane fluidity
    node_type: QUALITY
    description: Physical state of the cytoplasmic membrane supporting transport and
      bioenergetics.
    grounding: METPO:1007505
  - node_id: facultative_lipid_remodeling
    label: facultative lipid remodeling
    node_type: BIOLOGICAL_PROCESS
    description: Cold-induced shifts in lipid composition without obligate low-temperature
      specialization.
  - node_id: cold_shock_response
    label: cold-shock response
    node_type: BIOLOGICAL_PROCESS
    description: Cold-shock-protein induction supporting transient low-temperature
      acclimation.
  - node_id: membrane_rigidification
    label: membrane rigidification and thickening
    node_type: QUALITY
    description: Cold-induced increase in membrane order and bilayer thickness approaching
      a gel-phase transition.
  - node_id: unsaturated_hopanoids
    label: unsaturated hopanoids
    node_type: CHEMICAL
    description: Hopanoid lipids whose unsaturation rises at low temperature, aiding
      membrane homeostasis.
  - node_id: compatible_solute_accumulation
    label: compatible solute accumulation
    node_type: BIOLOGICAL_PROCESS
    description: Accumulation of compatible solutes that stabilize proteins and membranes
      under cold stress.
  - node_id: protein_membrane_stability
    label: protein and membrane stability under cold stress
    node_type: QUALITY
    description: Maintained integrity of proteins and membranes during low-temperature
      stress.
  - node_id: extracellular_polymeric_substances
    label: extracellular polymeric substances (EPS)
    node_type: CHEMICAL
    description: Secreted polymeric matrix surrounding cells that acts as a cryoprotectant.
  - node_id: freeze_thaw_cryoprotection
    label: cryoprotection against freeze-thaw cycles
    node_type: BIOLOGICAL_PROCESS
    description: Protection of cells from damage during freeze-thaw cycling.
  - node_id: growth_at_4c
    label: growth at 4 degrees C
    node_type: CAPACITY
    description: Ability to grow at refrigeration-range low temperature (4 C).
  edges:
  - subject: low_temperature
    predicate: decreases
    object: membrane_fluidity
    description: Low temperature reduces membrane fluidity, requiring compensation.
    evidence:
    - reference: DOI:10.1038/sj.embor.7400662
      snippet: decreased membrane fluidity
      notes: Supports cold-end membrane stress as the physical challenge for psychrotolerant
        growth.
    predicate_id: RO:0002212
  - subject: facultative_lipid_remodeling
    predicate: regulates
    object: membrane_fluidity
    description: Facultative lipid remodeling maintains workable membrane fluidity
      at low temperature.
    evidence:
    - reference: DOI:10.1146/annurev-micro-091313-103612
      snippet: more unsaturated fatty acids
      notes: Supports homoviscous adaptation as the mechanism employed under cold
        exposure.
    predicate_id: RO:0002211
  - subject: cold_shock_response
    predicate: enables
    object: psychrotolerant_trait
    description: The cold-shock response enables acclimation to low temperature without
      obligate cold dedication.
    evidence:
    - reference: DOI:10.1038/sj.embor.7400662
      snippet: Cold-shock proteins have also been described
      notes: Supports cold-shock proteins as a hallmark facultative-cold adaptation.
    predicate_id: RO:0002327
  - subject: facultative_lipid_remodeling
    predicate: manifests as
    object: psychrotolerant_trait
    description: Facultative lipid remodeling at low temperature manifests the psychrotolerant
      trait in representative organisms.
    evidence:
    - reference: DOI:10.1099/ijs.0.65141-0
      snippet: Pseudomonas guineae sp. nov., a novel psychrotolerant bacterium
      notes: Supports the trait endpoint in a representative organism.
    predicate_id: METPO:2007400
  - subject: low_temperature
    predicate: causes
    object: membrane_rigidification
    description: A low-temperature shift causes membrane rigidification and thickening
      toward a gel-phase transition.
    evidence:
    - reference: DOI:10.1128/spectrum.03925-23
      notes: Cold shock causes membrane rigidification and concomitant thickening,
        potentially culminating in a gel-phase transition.
    predicate_id: biolink:causes
  - subject: low_temperature
    predicate: increases
    object: unsaturated_hopanoids
    description: Decreasing growth temperature increases the unsaturated hopanoid
      fraction as a compositional cold adaptation.
    evidence:
    - reference: DOI:10.1007/s42770-023-01057-4
      notes: As the growth temperature decreased from 20 to 4 C, the total percent
        of unsaturated hopanoids increased from 27 to 49%.
    predicate_id: RO:0002213
  - subject: compatible_solute_accumulation
    predicate: protects
    object: protein_membrane_stability
    description: Compatible solute accumulation stabilizes proteins and membranes
      during low-temperature stress.
    evidence:
    - reference: DOI:10.37256/amtt.5220244537
      notes: Compatible solutes depress freezing point, stabilize proteins and membranes,
        scavenge radicals, and act as cryoprotectants.
  - subject: extracellular_polymeric_substances
    predicate: provides
    object: freeze_thaw_cryoprotection
    description: EPS surrounding cells provide cryoprotection against freeze-thaw
      cycles.
    evidence:
    - reference: DOI:10.37256/amtt.5220244537
      notes: EPS surrounding cells play a critical role in cold adaptation by providing
        protection against freeze-thaw cycles and acting as cryoprotectants.
  - subject: psychrotolerant_trait
    predicate: has capability
    object: growth_at_4c
    description: The psychrotolerant trait entails the capacity to grow at low temperatures
      such as 4 C while retaining higher optimal temperatures.
    evidence:
    - reference: DOI:10.1007/s42770-023-01057-4
      notes: Psychrotolerant/psychrotroph microbes can grow at 4 C and have optimal
        growth temperatures above 20 C.
curation_history:
- timestamp: '2026-05-05T01:35:46.859611+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-06T14:58:45-07:00'
  curator: codex
  action: CURATED_WITH_ORGANISM_EXAMPLE
  changes: Added Pseudomonas guineae organism example with PMID-backed evidence.
  llm_assisted: true
- timestamp: '2026-05-13T11:30:00-07:00'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added DOI-backed causal graph linking facultative cold adaptation (lipid
    remodeling and cold-shock response) to the psychrotolerant trait.
  llm_assisted: true
- timestamp: '2026-05-13T22:45:00-07:00'
  curator: codex
  action: IMPROVED_CAUSAL_GRAPH_EVIDENCE
  changes: Replaced Pseudomonas guineae PMID fallback with the article DOI in definition,
    record evidence, and CausalEdge evidence.
  llm_assisted: true
- timestamp: '2026-05-20T03:35:30Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×1).
  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:2007400×1).
  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: '2026-05-24T04:13:21Z'
  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: '2026-05-24T04:38:00Z'
  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: '2026-05-26T02:30:13Z'
  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 5 evidence-backed generic edges (7 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