identifier: METPO:1000474 label: pH delta low definition: A pH delta phenotype with a growth-supporting pH breadth of approximately 1–2 pH units, characteristic of organisms with limited pH-tolerance breadth. definition_source: DOI:10.1038/nrmicro2549 trait_category: ENVIRONMENT term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000232 synonyms: - synonym_text: pHd_1_2 synonym_type: RELATED_SYNONYM source: metpo.owl evidence: - reference: DOI:10.1038/nrmicro2549 snippet: pH homeostasis notes: pH-homeostasis review supports limited pH-homeostasis flexibility as the basis for a narrow pH-tolerance breadth. causal_graphs: - graph_id: ph_delta_low_limited_breadth title: pH-delta-low limited-breadth pH homeostasis description: DOI-backed graph linking limited pH-homeostasis flexibility to a pH growth breadth of approximately 1–2 pH units. nodes: - node_id: ph_delta_low_trait label: pH delta low node_type: TRAIT grounding: METPO:1000474 description: pH growth-supporting breadth approximately 1–2 pH units. - node_id: ph_delta label: pH delta node_type: TRAIT grounding: METPO:1000232 description: Breadth of the growth-supporting external pH range. - node_id: limited_ph_homeostasis label: limited pH-homeostasis flexibility node_type: BIOLOGICAL_PROCESS description: Modest capacity to remodel proton extrusion and envelope buffering across small pH shifts. - node_id: external_ph_stress label: external pH stress node_type: ENVIRONMENTAL_FACTOR description: External pH values outside the range maintainable as cytoplasmic pH. - node_id: cytoplasmic_ph_homeostasis label: cytoplasmic pH homeostasis node_type: BIOLOGICAL_PROCESS description: Maintenance of growth-permissive intracellular pH across external pH change. grounding: GO:0051453 - node_id: pmf_architecture label: proton motive force architecture node_type: BIOLOGICAL_PROCESS description: Tuning of Delta-psi and Delta-pH components of the proton motive force. - node_id: ph_homeostasis_capacity label: pH homeostasis capacity node_type: CAPACITY description: Capacity to balance and maintain cytoplasmic pH under pH stress. - node_id: weak_organic_acids label: weak organic acids node_type: CHEMICAL description: Uncharged weak acids that cross membranes and perturb the proton gradient. - node_id: delta_ph label: delta pH / cytoplasmic pH node_type: STATE description: Trans-membrane proton gradient and resulting cytoplasmic pH. - node_id: electrogenic_na_h_antiport label: electrogenic Na+/H+ antiport node_type: BIOLOGICAL_PROCESS description: Inward proton transport via cation/proton antiport driven by membrane potential. - node_id: alkaline_ph_homeostasis label: alkaline pH homeostasis node_type: BIOLOGICAL_PROCESS description: Maintenance of cytoplasmic pH under alkaline external conditions. - node_id: f1fo_atpase label: F1Fo-ATPase node_type: GENE_OR_PROTEIN description: Proton-coupled ATPase that expels or imports H+ using or generating PMF. edges: - subject: limited_ph_homeostasis predicate: produces object: ph_delta_low_trait description: Limited pH-homeostasis flexibility yields a 1–2 pH-unit pH-delta breadth. evidence: - reference: DOI:10.1038/nrmicro2549 snippet: pH homeostasis notes: Supports limited pH-homeostasis flexibility as the basis of narrow breadth. predicate_id: METPO:2000202 - subject: ph_delta_low_trait predicate: is a object: ph_delta description: pH delta low is a quantitative bin of the pH-delta phenotype. evidence: - reference: DOI:10.1016/j.tim.2007.02.005 snippet: proton motive force notes: Supports the 1–2 unit breadth as a value within the pH-delta distribution. predicate_id: rdfs:subClassOf - subject: external_ph_stress predicate: challenges object: cytoplasmic_ph_homeostasis description: External pH outside the maintainable cytoplasmic range challenges pH homeostasis. evidence: - reference: DOI:10.1038/nrmicro2549 notes: Diverse mechanisms for pH sensing and cytoplasmic pH homeostasis enable most bacteria to tolerate external pH outside the cytoplasmic range; general across bacteria. predicate_id: METPO:2007406 - subject: pmf_architecture predicate: determines object: ph_homeostasis_capacity description: PMF architecture (Delta-psi and Delta-pH balancing) determines pH homeostasis capacity. evidence: - reference: DOI:10.1038/nrmicro2549 notes: Bacteria tune and even reverse the relative magnitudes of Delta-psi and Delta-pH under pH stress; strong general mechanistic edge. - subject: weak_organic_acids predicate: perturbs object: delta_ph description: Weak organic acids cross the membrane and perturb the proton gradient / cytoplasmic pH. evidence: - reference: DOI:10.1038/nrmicro2549 notes: Uncharged weak-acid forms cross membranes and become trapped when charged, perturbing Delta-pH; general chemical-factor edge. - subject: electrogenic_na_h_antiport predicate: supports object: alkaline_ph_homeostasis description: Electrogenic Na+/H+ antiport supports cytoplasmic pH homeostasis under alkaline stress. evidence: - reference: DOI:10.1038/nrmicro2549 notes: Under alkaline stress, inward proton transport through cation/proton antiporters is crucial; strong general transporter-mediated edge. - subject: f1fo_atpase predicate: contributes to object: cytoplasmic_ph_homeostasis description: F1Fo-ATPase contributes to cytoplasmic pH homeostasis by expelling or importing H+. evidence: - reference: DOI:10.1038/nrmicro2549 notes: Respiratory complexes and proton-coupled ATPases use or generate PMF to expel or import H+; general higher-level edge. predicate_id: RO:0002326 curation_history: - timestamp: '2026-05-05T01:35:46.838505+00:00' curator: seed_from_metpo action: SEEDED_FROM_METPO changes: imported from data/raw/metpo.owl (CLASS) llm_assisted: false - timestamp: '2026-05-13T10:00:00-07:00' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added DOI-backed definition and causal graph linking limited pH-homeostasis flexibility to the narrow-breadth pH-delta-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: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 5 evidence-backed generic edges (9 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 (METPO:2007406×1, RO:0002326×1). llm_assisted: true - timestamp: '2026-06-24T17:21:17Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0051453×1). llm_assisted: true