identifier: METPO:1000622
label: halotolerant
definition: A halophily preference in which an organism can tolerate high salt concentrations
  but does not require them for growth.
definition_source: DOI:10.1093/femsre/fuy009
trait_category: ENVIRONMENT
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000629
evidence:
- reference: DOI:10.1093/femsre/fuy009
  snippet: highly halotolerant representatives
  notes: Supports halotolerant microorganisms as high-salt tolerant without strict
    salt requirement.
- reference: PMID:27621824
  snippet: Halomonas massiliensis sp. nov., a new halotolerant bacterium
  notes: 'Organism example: Halomonas massiliensis is described as halotolerant.'
canonical_examples:
- taxon_id: NCBITaxon:1570
  taxon_label: Halobacillus halophilus
  note: "Model halotolerant/moderately halophilic bacterium (chloride-dependent osmoadaptation). Staphylococcus aureus is the classic salt-tolerant clinical exemplar."
  reference: PMID:18442383
causal_graphs:
- graph_id: halotolerant_salt_stress_response
  title: Halotolerant salt-stress response mechanism
  description: Evidence-backed causal sketch linking halotolerance to survival under
    high salinity without strict salt requirement.
  nodes:
  - node_id: halotolerant_trait
    label: halotolerant
    node_type: TRAIT
    grounding: METPO:1000622
    description: Tolerates high salt but does not require it for growth.
  - node_id: high_salt_exposure
    label: high-salt exposure
    node_type: ENVIRONMENTAL_FACTOR
    description: Salt stress condition tolerated by the organism.
  - node_id: osmotic_stress
    label: osmotic stress
    node_type: BIOLOGICAL_PROCESS
    description: Cellular stress caused by external salinity.
    grounding: GO:0006970
  - node_id: compatible_solutes
    label: compatible solutes
    node_type: CHEMICAL
    description: Organic osmolytes that support salt tolerance.
    grounding: CHEBI:25728
  - node_id: compatible_solute_transport
    label: compatible-solute transport
    node_type: MOLECULAR_FUNCTION
    description: Uptake systems importing osmoprotectants under high-salt stress.
  - node_id: stress_protection
    label: stress protection
    node_type: BIOLOGICAL_PROCESS
    description: Protective cellular response to saline conditions.
  - node_id: compatible_solute_accumulation
    label: compatible solute accumulation
    node_type: BIOLOGICAL_PROCESS
    description: Intracellular buildup of organic osmolytes in response to osmotic
      stress.
  - node_id: salt_out_strategy
    label: salt-out strategy
    node_type: BIOLOGICAL_PROCESS
    description: Osmoadaptation strategy keeping cytoplasmic salt low while accumulating
      compatible solutes.
  - node_id: ectABC_operon
    label: ectABC operon
    node_type: GENE_OR_PROTEIN
    description: Gene cluster encoding ectoine biosynthesis from aspartate.
  - node_id: ectoine_biosynthesis
    label: ectoine biosynthesis
    node_type: BIOLOGICAL_PROCESS
    description: De novo synthesis of the compatible solute ectoine.
    grounding: GO:0019491
  - node_id: betA_betB
    label: betA/betB
    node_type: GENE_OR_PROTEIN
    description: Choline oxidation enzymes producing glycine betaine.
  - node_id: glycine_betaine_biosynthesis
    label: glycine betaine biosynthesis
    node_type: BIOLOGICAL_PROCESS
    description: Synthesis of the compatible solute glycine betaine from environmental
      choline.
    grounding: GO:0031456
  edges:
  - subject: high_salt_exposure
    predicate: tolerated by
    object: halotolerant_trait
    description: Halotolerant organisms can survive elevated salinity without requiring
      it.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: highly halotolerant representatives
      notes: Review distinguishes halotolerant microorganisms in high-salt environments.
  - subject: high_salt_exposure
    predicate: causes
    object: osmotic_stress
    description: External salinity creates osmotic stress in halotolerant organisms.
    evidence:
    - reference: DOI:10.1186/1746-1448-4-2
      snippet: high salt concentrations in the environment
      notes: Review supports high environmental salt as the stress context.
    predicate_id: biolink:causes
  - subject: compatible_solutes
    predicate: mitigates
    object: osmotic_stress
    description: Compatible solutes are a mechanism for tolerating salt stress.
    evidence:
    - reference: DOI:10.1093/femsre/fuy009
      snippet: organic osmotic solutes
      notes: Supports organic osmotic solutes as an osmoadaptation strategy.
    predicate_id: METPO:2007407
  - subject: compatible_solute_transport
    predicate: imports
    object: compatible_solutes
    description: Uptake systems import osmoprotectants that support halotolerance.
    evidence:
    - reference: DOI:10.1016/j.csbj.2021.01.030
      snippet: biosynthesis and/or uptake of compatible solutes
      notes: Adds explicit source support for transport-mediated compatible-solute
        accumulation in bacterial salt-stress responses.
    predicate_id: METPO:2000208
  - subject: compatible_solutes
    predicate: contributes to
    object: stress_protection
    description: Compatible solutes can stabilize cells under saline stress.
    evidence:
    - reference: DOI:10.1139/cjm-2014-0233
      snippet: stabilizers of intracellular proteins
      notes: Haloalkaliphile review supports compatible solutes as stabilizing osmoprotectants;
        mechanism is shared with halotolerance.
    predicate_id: RO:0002326
  - subject: stress_protection
    predicate: enables
    object: halotolerant_trait
    description: Stress-protection mechanisms allow tolerance of salt exposure.
    evidence:
    - reference: DOI:10.1371/journal.pone.0168818
      snippet: allows microorganisms to cope with high salinities
      notes: Supports osmoadaptation as a mechanism for growth under salt stress.
    predicate_id: RO:0002327
  - subject: osmotic_stress
    predicate: increases
    object: compatible_solute_accumulation
    description: Osmotic stress drives accumulation of compatible solutes.
    evidence:
    - reference: DOI:10.58088/07hg-r941
      notes: Compatible solutes are accumulated in response to osmotic stress; broad
        mechanistic claim across marine bacteria.
    predicate_id: RO:0002213
  - subject: salt_out_strategy
    predicate: relies on
    object: compatible_solute_accumulation
    description: The salt-out osmoadaptation strategy relies on accumulation or de
      novo synthesis of compatible solutes.
    evidence:
    - reference: DOI:10.1038/s41598-024-63581-z
      notes: '''salt-out''/''low-salt-high-compatible-solute-in-cytoplasm'' strategy
        relies on accumulation or de-novo synthesis of organic compatible solutes;
        directly supports halotolerant scope.'
  - subject: ectABC_operon
    predicate: enables
    object: ectoine_biosynthesis
    description: The ectABC operon synthesizes ectoine de novo from aspartic acid.
    evidence:
    - reference: DOI:10.58088/07hg-r941
      notes: Ectoine is synthesized de novo from aspartic acid via the ectABC operon;
        general bacterial mechanism.
    predicate_id: RO:0002327
  - subject: betA_betB
    predicate: enables
    object: glycine_betaine_biosynthesis
    description: betA and betB produce glycine betaine from environmental choline.
    evidence:
    - reference: DOI:10.58088/07hg-r941
      notes: Glycine betaine is produced from environmental choline via betA and betB;
        canonical pathway edge, broadly applicable.
    predicate_id: RO:0002327
  - subject: ectoine_biosynthesis
    predicate: produces
    object: compatible_solutes
    description: Ectoine biosynthesis yields a compatible solute supporting salt tolerance.
    evidence:
    - reference: DOI:10.58088/07hg-r941
      notes: Ectoine is a compatible solute synthesized de novo via the ectABC operon.
    predicate_id: METPO:2000202
  - subject: glycine_betaine_biosynthesis
    predicate: produces
    object: compatible_solutes
    description: Glycine betaine biosynthesis yields a compatible solute supporting
      salt tolerance.
    evidence:
    - reference: DOI:10.58088/07hg-r941
      notes: Glycine betaine is produced from environmental choline and acts as a
        compatible solute.
    predicate_id: METPO:2000202
curation_history:
- timestamp: '2026-05-05T01:35:46.861954+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-06T14:15:44-07:00'
  curator: codex
  action: CURATED_WITH_ORGANISM_EXAMPLE
  changes: Added Halomonas massiliensis organism example with PMID-backed evidence.
  llm_assisted: true
- timestamp: '2026-05-10T00:00:00-07:00'
  curator: codex
  action: ADDED_CAUSAL_GRAPH
  changes: Added DOI-backed causal graph for halotolerant salt-stress response.
  llm_assisted: true
- timestamp: '2026-05-11T00:00:00-07:00'
  curator: codex
  action: CURATED_WITH_LITERATURE
  changes: Replaced PMID definition source with DOI-backed halotolerance source and
    added a compatible-solute transport edge to the existing causal graph.
  llm_assisted: true
- timestamp: '2026-05-20T03:35:29Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002326×1, RO:0002327×1).
  llm_assisted: true
- timestamp: '2026-05-20T05:49:24Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (biolink:causes×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:2007407×1).
  llm_assisted: true
- timestamp: '2026-05-24T04:38:00Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (GO:0006970×1, CHEBI:65015×1).
  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: '2026-06-16T06:30:55Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2000208×1).
  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 (6 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:10Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 5 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×2, METPO:2000202×2, RO:0002213×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:30Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv
    (GO:0019491×1, GO:0031456×1).
  llm_assisted: true