identifier: traitmech:000002 label: obligately piezophilic definition: A pressure growth preference in which an organism requires elevated hydrostatic pressure for growth and is unable to grow at atmospheric pressure (0.1 MPa). definition_source: DOI:10.1038/srep27289 trait_category: ENVIRONMENT term_kind: CLASS mapping_status: REVIEWED parent_traits: - traitmech:000001 synonyms: - synonym_text: obligate piezophile synonym_type: EXACT_SYNONYM source: DOI:10.1038/srep27289 evidence: - reference: DOI:10.1038/srep27289 snippet: High hydrostatic pressure adaptive strategies in an obligate piezophile Pyrococcus yayanosii notes: 'Organism example: Pyrococcus yayanosii is an obligate piezophile that requires high hydrostatic pressure for growth.' - reference: DOI:10.1099/ijsem.0.001671 snippet: growth range of 80-140 MPa (optimum, 120 MPa) at 6 degrees C notes: 'Organism example: Colwellia marinimaniae MTCD1 grows only at high pressure (80-140 MPa) and does not grow near atmospheric pressure.' canonical_examples: - taxon_id: NCBITaxon:1513592 taxon_label: Colwellia marinimaniae note: "Most piezophilic organism described; optimum ~120 MPa (Mariana Trench). Photobacterium profundum SS9 is the classic genetic model." reference: https://pubmed.ncbi.nlm.nih.gov/27902293/ causal_graphs: - graph_id: obligate_piezophily_high_pressure_requirement title: 'Obligate piezophily: growth requires elevated hydrostatic pressure' description: Evidence-backed causal sketch linking obligate HHP adaptation to inability to grow at atmospheric pressure. nodes: - node_id: obligate_piezophilic_trait label: obligately piezophilic node_type: TRAIT grounding: traitmech:000002 description: Growth restricted to elevated hydrostatic pressures. - node_id: obligate_hhp label: obligate high hydrostatic pressure node_type: ENVIRONMENTAL_FACTOR description: Hydrostatic pressure level required for growth (no growth at 0.1 MPa). - node_id: pressure_dependent_machinery label: pressure-dependent cellular machinery node_type: BIOLOGICAL_PROCESS description: Membrane, ribosome, and replication systems adapted only to HHP. - node_id: ambient_pressure_growth_failure label: inability to grow at ambient pressure (0.1 MPa) node_type: QUALITY description: Obligate piezophiles cannot grow at atmospheric pressure (0.1 MPa). - node_id: membrane_unsaturated_branched_lipids label: unsaturated/branched-chain membrane lipids node_type: CHEMICAL description: Membrane fatty acids with increased unsaturation/branching that maintain fluidity under HHP. - node_id: membrane_fluidity_maintenance label: maintenance of membrane fluidity under HHP node_type: BIOLOGICAL_PROCESS description: Homeoviscous adaptation preserving membrane fluidity at elevated hydrostatic pressure. edges: - subject: obligate_hhp predicate: causes object: obligate_piezophilic_trait description: HHP adaptation that no longer functions at 0.1 MPa makes high pressure obligatory for growth. evidence: - reference: DOI:10.1099/ijsem.0.001671 notes: Colwellia marinimaniae MTCD1 has a growth range of 80-140 MPa (optimum 120 MPa) and does not grow at atmospheric pressure. predicate_id: biolink:causes - subject: pressure_dependent_machinery predicate: enables object: obligate_piezophilic_trait description: Cellular machinery requiring HHP for function realizes the obligate-piezophile phenotype. evidence: - reference: DOI:10.1038/srep27289 notes: Pyrococcus yayanosii is an obligate piezophile requiring HHP for growth. predicate_id: RO:0002327 - subject: obligate_piezophilic_trait predicate: has characteristic object: ambient_pressure_growth_failure description: The obligate-piezophile phenotype is defined by inability to grow at ambient pressure (0.1 MPa). evidence: - reference: DOI:10.1038/s41396-021-00930-0 notes: Obligate piezophiles (or hyperpiezophiles) are unable to grow at ambient pressure (0.1 MPa). - subject: obligate_hhp predicate: increases amount of object: membrane_unsaturated_branched_lipids description: Elevated hydrostatic pressure increases the requirement for and abundance of unsaturated/branched-chain membrane lipids. evidence: - reference: DOI:10.3389/fmolb.2022.1058381 notes: The abundance of specific membrane lipids, such as those containing unsaturated and branched-chain fatty acids, rises with increasing HHP across marine piezophiles. - subject: membrane_unsaturated_branched_lipids predicate: enables object: membrane_fluidity_maintenance description: Unsaturated/branched-chain lipids maintain membrane fluidity under HHP (homeoviscous adaptation). evidence: - reference: DOI:10.3389/fmolb.2022.1058381 notes: Membrane lipid adaptation (unsaturated/branched fatty acids) is a homeoviscous response maintaining membrane fluidity under high hydrostatic pressure. predicate_id: RO:0002327 - subject: membrane_fluidity_maintenance predicate: contributes to object: pressure_dependent_machinery description: Maintained membrane fluidity supports the pressure-dependent cellular machinery underlying obligate piezophily. evidence: - reference: DOI:10.3389/fmolb.2022.1058381 notes: Membrane fluidity maintenance via lipid adaptation underlies the pressure-adapted membrane systems of piezophiles. predicate_id: RO:0002326 curation_history: - timestamp: '2026-05-28T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate ENVIRONMENT trait (obligate high-pressure requirement) from literature research; sub-variant of piezophilic. Backed by two obligate- piezophile organism examples. llm_assisted: true - timestamp: '2026-06-09T14:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (obligate HHP requirement) with RO/biolink predicate groundings; promoted PROPOSED to REVIEWED. llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 4 evidence-backed generic edges (3 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 (RO:0002327×1, RO:0002326×1). llm_assisted: true