identifier: traitmech:000068 label: polyphosphate granule definition: An intracellular storage inclusion of inorganic polyphosphate (a polymer of many phosphate residues), historically called a volutin or metachromatic granule, serving as a phosphate and energy reserve. definition_source: DOI:10.1146/annurev.biochem.77.083007.093039 trait_category: MORPHOLOGY term_kind: CLASS mapping_status: REVIEWED parent_traits: - traitmech:000066 synonyms: - synonym_text: volutin granule synonym_type: RELATED_SYNONYM source: DOI:10.1146/annurev.biochem.77.083007.093039 - synonym_text: metachromatic granule synonym_type: RELATED_SYNONYM source: DOI:10.1146/annurev.biochem.77.083007.093039 evidence: - reference: DOI:10.1146/annurev.biochem.77.083007.093039 notes: Rao, Gómez-García & Kornberg review inorganic polyphosphate, accumulated as granules, as a phosphate/energy reserve essential for growth and survival. - reference: DOI:10.1038/s41579-020-0413-0 notes: Greening & Lithgow include polyphosphate bodies among bacterial intracellular inclusions. canonical_examples: - taxon_id: NCBITaxon:29405 taxon_label: Microlunatus phosphovorus note: "Model polyphosphate-accumulating organism (volutin granules; enhanced biological phosphorus removal)." reference: PMID:22923697 causal_graphs: - graph_id: polyphosphate_granule_storage title: Polyphosphate granules store phosphate and energy as inorganic polyP description: Evidence-backed causal sketch linking inorganic polyphosphate accumulation to volutin/metachromatic granules supporting growth and survival. nodes: - node_id: polyp_granule_trait label: polyphosphate granule node_type: TRAIT grounding: traitmech:000068 description: Cytoplasmic inclusion of inorganic polyphosphate. - node_id: inorganic_polyphosphate label: inorganic polyphosphate node_type: CHEMICAL description: Polymer of many phosphate residues stored as a granule. - node_id: phosphate_energy_reserve label: phosphate / energy reserve node_type: QUALITY description: Reservoir of phosphate and high-energy phosphoanhydride bonds. - node_id: ppk label: polyphosphate kinase (PPK) node_type: GENE_OR_PROTEIN description: Enzyme that synthesizes inorganic polyphosphate from ATP. - node_id: ppx label: exopolyphosphatase (PPX) node_type: GENE_OR_PROTEIN description: Enzyme that degrades inorganic polyphosphate. - node_id: divalent_cations label: divalent cations node_type: CHEMICAL description: Divalent metal cations (Ca2+, Mg2+, Fe2+/Fe3+, Zn2+) bound by polyP. - node_id: stress_survival label: stress survival / stress response node_type: BIOLOGICAL_PROCESS description: Survival during stationary phase, nutrient starvation, and stress. edges: - subject: inorganic_polyphosphate predicate: located in object: polyp_granule_trait description: Inorganic polyphosphate accumulates as granules in the cytoplasm. evidence: - reference: DOI:10.1146/annurev.biochem.77.083007.093039 notes: Rao, Gómez-García & Kornberg review polyphosphate accumulation as granules. predicate_id: biolink:located_in - subject: polyp_granule_trait predicate: contributes to object: phosphate_energy_reserve description: PolyP granules supply phosphate and energy for growth and survival. evidence: - reference: DOI:10.1038/s41579-020-0413-0 notes: Greening & Lithgow include polyphosphate bodies among bacterial intracellular inclusions. predicate_id: RO:0002326 - subject: ppk predicate: synthesizes object: inorganic_polyphosphate description: Polyphosphate kinase (PPK) synthesizes inorganic polyP using ATP. evidence: - reference: DOI:10.1371/journal.pbio.3002558 notes: Polyphosphate is synthesized by polyphosphate kinase (PPK), which rapidly synthesizes polyP using ATP as a co-substrate. - subject: ppx predicate: degrades object: inorganic_polyphosphate description: Exopolyphosphatase (PPX) degrades inorganic polyphosphate. evidence: - reference: DOI:10.1371/journal.pbio.3002558 notes: Polyphosphate is degraded by exopolyphosphatase PPX; canonical core metabolism edge. predicate_id: METPO:2000007 - subject: inorganic_polyphosphate predicate: binds object: divalent_cations description: PolyP chelates/binds divalent cations, affecting polyP biophysics and granule composition. evidence: - reference: DOI:10.3390/biom14080937 notes: PolyP granules contain associated cations; polyP can bind iron and inhibit Fenton chemistry. Strong general biochemical edge. - subject: inorganic_polyphosphate predicate: promotes object: stress_survival description: PolyP accumulation promotes survival in stationary phase and nutrient starvation. evidence: - reference: DOI:10.3390/biom14080937 notes: PolyP serves as phosphate/energy storage and supports survival in stationary phase and nutrient starvation; ppk mutants show stress sensitivity. predicate_id: RO:0002213 curation_history: - timestamp: '2026-06-03T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate MORPHOLOGY trait (polyphosphate/volutin granule); storage sub-variant of intracellular inclusion. llm_assisted: true - timestamp: '2026-06-09T15:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (polyP granule phosphate/energy reserve) 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 (4 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:13Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×1). llm_assisted: true - timestamp: '2026-06-24T17:23:39Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000007×1). llm_assisted: true