identifier: METPO:1000697
label: gram stain
definition: A phenotype where microorganisms are grouped based on their ability to
  retain crystal violet dye in the Gram staining procedure.
definition_source: DOI:10.3109/10520299609117151
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000059
synonyms:
- synonym_text: Morphology.cell morphology.gram stain
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
- synonym_text: gram_stain
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
created_by: Luke Wang
evidence:
- reference: DOI:10.3109/10520299609117151
  snippet: retention of a crystal violet:iodine complex
  notes: Supports Gram staining as differential retention of crystal violet-iodine
    complex.
causal_graphs:
- graph_id: gram_stain_cell_envelope_retention
  title: Gram stain cell-envelope retention mechanism
  description: Evidence-backed causal sketch linking Gram stain phenotype to crystal
    violet-iodine complex formation, peptidoglycan architecture, outer membrane loss
    during decolorization, and counterstaining.
  nodes:
  - node_id: gram_stain_trait
    label: gram stain
    node_type: TRAIT
    grounding: METPO:1000697
    description: Differential staining phenotype based on retention of crystal violet
      dye.
  - node_id: crystal_violet
    label: crystal violet
    node_type: CHEMICAL
    description: Primary dye used in the Gram staining procedure.
    grounding: CHEBI:41688
  - node_id: iodine_mordant
    label: iodine mordant
    node_type: CHEMICAL
    description: Iodine solution that forms a dye-iodine complex with crystal violet.
  - node_id: crystal_violet_iodine_complex
    label: crystal violet-iodine complex
    node_type: CHEMICAL
    description: Dye complex retained or removed during Gram staining.
  - node_id: peptidoglycan_cell_wall
    label: peptidoglycan cell wall
    node_type: CELLULAR_LOCALIZATION
    grounding: GO:0009274
    description: Cell-wall polymer layer influencing stain retention.
  - node_id: outer_membrane
    label: outer membrane
    node_type: CELLULAR_LOCALIZATION
    description: Gram-negative cell-envelope membrane disrupted during decolorization.
    grounding: GO:0019867
  - node_id: alcohol_decolorization
    label: alcohol decolorization
    node_type: EXPERIMENTAL_FACTOR
    description: Decolorization step that differentiates Gram-positive and Gram-negative
      staining.
  edges:
  - subject: crystal_violet
    predicate: reacts with
    object: iodine_mordant
    description: Crystal violet and iodine form a dye complex during the Gram stain.
    evidence:
    - reference: DOI:10.1128/jb.156.2.837-845.1983
      snippet: produce a chemical precipitate
      notes: Supports chemical formation of the crystal violet-iodine precipitate.
  - subject: crystal_violet_iodine_complex
    predicate: is retained by
    object: peptidoglycan_cell_wall
    description: Cell-wall architecture determines whether the dye complex remains
      after decolorization.
    evidence:
    - reference: DOI:10.3109/10520299609117151
      snippet: cell wall ... responsible for retention
      notes: Review supports the Gram-positive cell wall as responsible for retaining
        the dye-iodine complex.
  - subject: alcohol_decolorization
    predicate: removes
    object: outer_membrane
    description: Decolorization disrupts the Gram-negative outer membrane and helps
      remove dye complex.
    evidence:
    - reference: DOI:10.1128/jb.156.2.837-845.1983
      snippet: alcohol-acetone decolorization
      notes: Supports decolorization as a chemical step differentiating Gram reactions.
  - subject: outer_membrane
    predicate: regulates
    object: gram_stain_trait
    description: The Gram-negative outer membrane contributes to dye loss and counterstain
      appearance.
    evidence:
    - reference: DOI:10.1038/s41579-019-0201-x
      snippet: defining feature of the Gram-negative cell envelope
      notes: Supports the outer membrane as a defining Gram-negative envelope feature.
    predicate_id: RO:0002211
  - subject: peptidoglycan_cell_wall
    predicate: causes
    object: gram_stain_trait
    description: Peptidoglycan thickness and envelope architecture determine Gram
      stain outcome.
    evidence:
    - reference: DOI:10.3109/10520299609117151
      snippet: mechanism of the Gram stain
      notes: Supports cell-wall mediated Gram reaction.
    predicate_id: biolink:causes
curation_history:
- timestamp: '2026-05-05T01:35:46.901879+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-11T00:00:00-07:00'
  curator: codex
  action: CURATED_WITH_LITERATURE
  changes: Reviewed Gram stain trait and added DOI-backed causal graph for crystal
    violet-iodine complex retention, peptidoglycan cell wall architecture, outer membrane
    influence, and alcohol decolorization.
  llm_assisted: true
- timestamp: '2026-05-24T04:38:00Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (GO:0019867×1).
  llm_assisted: true
- timestamp: '2026-05-26T05:00:48Z'
  curator: claude
  action: RENAME_PREDICATE_LABELS
  changes: 'Renamed 2 causal-edge predicate label(s) to align with existing groundings:
    influences → regulates ×1; determines → causes ×1.'
  llm_assisted: true
- timestamp: '2026-05-26T05:00:50Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002211×1, biolink:causes×1).
  llm_assisted: true
- timestamp: '2026-06-14T05:51:46Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:41688×1).
  llm_assisted: true