identifier: METPO:1000698 label: gram positive definition: A gram stain in which an organism retains crystal violet dye and appears purple under microscopy due to a thick peptidoglycan cell wall. definition_source: DOI:10.3109/10520299609117151 trait_category: MORPHOLOGY term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000697 synonyms: - synonym_text: G_positive synonym_type: RELATED_SYNONYM source: metpo.owl - synonym_text: positive synonym_type: RELATED_SYNONYM source: metpo.owl evidence: - reference: DOI:10.3109/10520299609117151 snippet: retention of a crystal violet:iodine complex notes: Supports Gram-positive phenotype as retention of crystal violet-iodine complex. - reference: PMID:16950365 snippet: Staphylococcus aureus is a gram-positive bacterium notes: 'Organism example: Staphylococcus aureus is described as Gram-positive.' canonical_examples: - taxon_id: NCBITaxon:1423 taxon_label: Bacillus subtilis note: "Model Gram-positive (thick peptidoglycan, no outer membrane); strain 168 is the workhorse." reference: PMID:9384377 causal_graphs: - graph_id: gram_positive_cell_wall_retention title: Gram-positive cell-wall dye retention mechanism description: Evidence-backed causal sketch linking Gram-positive staining to thick peptidoglycan, wall teichoic acids, low decolorizer permeability, and crystal violet-iodine retention. nodes: - node_id: gram_positive_trait label: gram positive node_type: TRAIT grounding: METPO:1000698 description: Gram stain phenotype in which cells retain crystal violet and appear purple. - node_id: thick_peptidoglycan_cell_wall label: thick peptidoglycan cell wall node_type: CELLULAR_LOCALIZATION description: Multilayered peptidoglycan wall characteristic of Gram-positive bacteria. - node_id: wall_teichoic_acids label: wall teichoic acids node_type: CHEMICAL description: Anionic cell-wall glycopolymers attached to Gram-positive peptidoglycan. - node_id: lipoteichoic_acids label: lipoteichoic acids node_type: CHEMICAL description: Membrane-anchored Gram-positive cell-wall glycopolymers. grounding: CHEBI:28640 - node_id: crystal_violet_iodine_complex label: crystal violet-iodine complex node_type: CHEMICAL description: Dye complex retained after decolorization. - node_id: alcohol_decolorization label: alcohol decolorization node_type: EXPERIMENTAL_FACTOR description: Gram stain step that removes dye complex from Gram-negative cells. - node_id: iodine_mordant label: iodine mordant node_type: CHEMICAL description: Iodine added during Gram staining that acts as a mordant binding crystal violet. - node_id: cv_iodine_complex_formation label: crystal violet-iodine complex formation node_type: BIOLOGICAL_PROCESS description: Formation of large crystal violet-iodine complexes within the cell during Gram staining. - node_id: peptidoglycan_mesh_low_porosity label: peptidoglycan mesh low porosity node_type: QUALITY description: Low physical porosity of the thick peptidoglycan mesh that traps the dye complex. - node_id: d_alanine_esters label: D-alanine esters on teichoic acids node_type: CHEMICAL description: D-alanine ester modifications on teichoic acids that neutralize phosphate negative charge. - node_id: teichoic_acid_negative_charge label: teichoic-acid negative charge node_type: QUALITY description: Anionic phosphate-rich negative charge contributed by teichoic acids. - node_id: d_alanylation_teichoic_acids label: D-alanylation of teichoic acids node_type: BIOLOGICAL_PROCESS description: Modification of wall and lipoteichoic acids with D-alanine esters. - node_id: positively_charged_cell_surface label: positively charged cell surface node_type: QUALITY description: More positively charged Gram-positive cell surface resulting from D-alanylation. edges: - subject: thick_peptidoglycan_cell_wall predicate: retains object: crystal_violet_iodine_complex description: Thick Gram-positive cell walls retain the dye-iodine complex during decolorization. evidence: - reference: DOI:10.3109/10520299609117151 snippet: cell wall ... responsible for retention notes: Supports retention of crystal violet-iodine complex by the Gram-positive cell wall. - subject: wall_teichoic_acids predicate: embedded in object: thick_peptidoglycan_cell_wall description: Wall teichoic acids are major glycopolymers in the Gram-positive wall matrix. evidence: - reference: DOI:10.1038/nrmicro1861 snippet: peptidoglycan-attached notes: Supports teichoic acids as peptidoglycan-attached Gram-positive wall polymers. predicate_id: biolink:located_in - subject: lipoteichoic_acids predicate: contributes to object: thick_peptidoglycan_cell_wall description: Lipoteichoic acids are membrane-attached glycopolymers in Gram-positive cell envelopes. evidence: - reference: DOI:10.1038/nrmicro1861 snippet: membrane-attached notes: Supports lipoteichoic acids as membrane-attached Gram-positive glycopolymers. predicate_id: RO:0002326 - subject: alcohol_decolorization predicate: fails to remove object: crystal_violet_iodine_complex description: Gram-positive cells retain dye complex after decolorization and remain purple. evidence: - reference: DOI:10.3109/10520299609117151 snippet: retention of a crystal violet:iodine complex notes: Supports retention during the Gram reaction. - subject: crystal_violet_iodine_complex predicate: produces object: gram_positive_trait description: Retained dye complex produces the observed Gram-positive staining phenotype. evidence: - reference: DOI:10.1128/jb.156.2.837-845.1983 snippet: crystal violet-iodine complex notes: Supports the dye complex as the chemical basis of staining. predicate_id: METPO:2000202 - subject: iodine_mordant predicate: causes object: cv_iodine_complex_formation description: Iodine acts as a mordant, interacting with crystal violet to form large complexes. evidence: - reference: DOI:10.52403/ijrr.20230934 notes: When iodine is added, it interacts with CV+ to form large complexes. predicate_id: biolink:causes - subject: cv_iodine_complex_formation predicate: produces object: crystal_violet_iodine_complex description: Formation of the crystal violet-iodine complex retained within the peptidoglycan mesh. evidence: - reference: DOI:10.1038/s42003-026-10072-8 notes: The Gram stain relies on retention of crystal violet-iodine complexes within the peptidoglycan mesh. predicate_id: METPO:2000202 - subject: peptidoglycan_mesh_low_porosity predicate: increases object: crystal_violet_iodine_complex description: Low-porosity thick peptidoglycan walls trap and retain the dye complex. evidence: - reference: DOI:10.1038/s42003-026-10072-8 notes: Crystal violet-iodine retention depends on the physical porosity of the peptidoglycan mesh; thick, low-porosity walls can trap the complex. predicate_id: RO:0002213 - subject: d_alanine_esters predicate: neutralizes object: teichoic_acid_negative_charge description: D-alanine esters neutralize the phosphate-rich negative charge of teichoic acids. evidence: - reference: DOI:10.1038/s41564-023-01411-0 notes: These polymers are commonly modified with D-alanine esters that neutralize phosphate-rich negative charge. - subject: d_alanylation_teichoic_acids predicate: increases object: positively_charged_cell_surface description: D-alanylation of both teichoic acid types leads to a more positively charged cell surface. evidence: - reference: DOI:10.1093/femsre/fuaa064 notes: D-alanylation of both teichoic acid types leads to a more positively charged cell surface. predicate_id: RO:0002213 - subject: wall_teichoic_acids predicate: influences object: positively_charged_cell_surface description: Wall teichoic acids and their anionic/cationic balance affect cell-surface charge. evidence: - reference: DOI:10.1146/annurev-micro-092412-155620 notes: WTAs anionic/cationic balance affects cell-surface charge and antimicrobial interactions. curation_history: - timestamp: '2026-05-05T01:35:46.902486+00:00' curator: seed_from_metpo action: SEEDED_FROM_METPO changes: imported from data/raw/metpo.owl (CLASS) llm_assisted: false - timestamp: '2026-05-06T14:40:41-07:00' curator: codex action: CURATED_WITH_ORGANISM_EXAMPLE changes: Added Staphylococcus aureus organism example with PMID-backed evidence. 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 Gram stain source and added causal graph for Gram-positive cell-wall dye retention, peptidoglycan, wall teichoic acids, and lipoteichoic acids. llm_assisted: true - timestamp: '2026-05-20T03:35:31Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002326×1, METPO:2000202×1). llm_assisted: true - timestamp: '2026-06-13T21:03:26Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:located_in×1). llm_assisted: true - timestamp: '2026-06-14T06:55:38Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:28640×1). llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 6 evidence-backed generic edges (7 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:13Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 4 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×2, biolink:causes×1, METPO:2000202×1). llm_assisted: true