identifier: METPO:1000696
label: triangular shaped
definition: A cell shape in which an organism forms flat, triangular or wedge-shaped
  cells.
definition_source: DOI:10.1146/annurev-cellbio-101011-155745
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000666
synonyms:
- synonym_text: triangular
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
evidence:
- reference: DOI:10.1146/annurev-cellbio-101011-155745
  snippet: cell shape is genetically determined
  notes: Cell-shape review supports anisotropic envelope architecture as the basis
    for non-round cell geometries such as triangles.
- reference: DOI:10.1146/annurev-micro-090816-093703
  snippet: archaeal cell shape
  notes: Archaeal cell-shape review supports unusual flat polygonal cells in halophilic
    archaea.
canonical_examples:
- taxon_id: NCBITaxon:29282
  taxon_label: Haloarcula japonica
  note: "Flat triangular/disc-shaped halophilic archaeon; textbook example of non-rod/coccus cell geometry."
  reference: DOI:10.1016/S0723-2020(11)80165-7
causal_graphs:
- graph_id: triangular_shaped_planar_polygonal_growth
  title: Triangular-shape planar polygonal envelope growth
  description: DOI-backed graph linking planar anisotropic envelope growth and S-layer-constrained
    polygonal geometry to flat triangular cells.
  nodes:
  - node_id: triangular_shaped_trait
    label: triangular shaped
    node_type: TRAIT
    grounding: METPO:1000696
    description: Flat triangular or wedge-shaped cell geometry.
  - node_id: planar_envelope_growth
    label: planar envelope growth
    node_type: BIOLOGICAL_PROCESS
    description: Cell-envelope expansion in a 2D plane.
  - node_id: slayer_constraints
    label: S-layer constraints
    node_type: ORGANELLE
    description: Paracrystalline S-layer imposing geometric constraints on shape.
    grounding: GO:0030115
  - node_id: polygonal_geometry
    label: polygonal geometry
    node_type: BIOLOGICAL_PROCESS
    description: Flat, angular cell geometry with defined edges.
  - node_id: rigid_slayer_sheets
    label: rigid S-layer sheets
    node_type: ORGANELLE
    description: Overlapping paracrystalline S-layer sheets cross-linked by a dense
      net of protein bridges, producing high mechanical rigidity.
  - node_id: outer_membrane
    label: outer membrane
    node_type: CELLULAR_LOCALIZATION
    description: Cell outer membrane that conforms to the angular polygonal envelope
      geometry.
    grounding: GO:0019867
  - node_id: peptidoglycan_layer
    label: peptidoglycan layer
    node_type: CELLULAR_LOCALIZATION
    description: Peptidoglycan-based cell wall layer that does not adopt the polygonal
      cell shape.
  edges:
  - subject: planar_envelope_growth
    predicate: enables
    object: polygonal_geometry
    description: Planar envelope growth allows flat polygonal cell forms.
    evidence:
    - reference: DOI:10.1146/annurev-micro-090816-093703
      snippet: archaeal cell shape
      notes: Supports planar growth as the basis for flat archaeal cells.
    predicate_id: RO:0002327
  - subject: slayer_constraints
    predicate: causes
    object: polygonal_geometry
    description: S-layer geometry constrains the cell into angular polygonal forms.
    evidence:
    - reference: DOI:10.1146/annurev-cellbio-101011-155745
      snippet: cell shape is genetically determined
      notes: Supports envelope-architecture constraints (e.g., S-layer) as shape determinants.
    predicate_id: biolink:causes
  - subject: polygonal_geometry
    predicate: manifests as
    object: triangular_shaped_trait
    description: Angular polygonal geometry manifests the triangular-shaped trait.
    evidence:
    - reference: DOI:10.1146/annurev-micro-090816-093703
      snippet: archaeal cell shape
      notes: Supports the trait endpoint in triangular halophilic archaea.
    predicate_id: METPO:2007400
  - subject: slayer_constraints
    predicate: determines
    object: polygonal_geometry
    description: The S-layer is the determining factor for the polygonal (angular)
      cell shape.
    evidence:
    - reference: DOI:10.3389/fmicb.2021.766527
      notes: Cryo-ET shows "the S-layer is the determining factor for their polygonal
        cell shape"; generic S-layer-driven polygonal envelope mechanism.
  - subject: rigid_slayer_sheets
    predicate: confers rigidity to
    object: polygonal_geometry
    description: Very rigid, protein-bridge-cross-linked S-layer sheets confer mechanical
      rigidity that stabilizes the angular polygonal morphology.
    evidence:
    - reference: DOI:10.3389/fmicb.2021.766527
      notes: '"these S-layer sheets are very rigid" and a "dense net of protein bridges...
        establishes the observed rigidity"; structural stabilization of angular morphology.'
  - subject: polygonal_geometry
    predicate: shapes
    object: outer_membrane
    description: The outer membrane conforms to (follows) the polygonal cell shape
      imposed by the envelope.
    evidence:
    - reference: DOI:10.3389/fmicb.2021.766527
      notes: '"the outer membrane followed the polygonal cell shape"; outer membrane
        is a participant conforming to polygonal geometry.'
  - subject: polygonal_geometry
    predicate: does not shape
    object: peptidoglycan_layer
    description: The peptidoglycan layer does not adopt the polygonal cell shape,
      bounding the mechanism to S-layer and outer membrane.
    evidence:
    - reference: DOI:10.3389/fmicb.2021.766527
      notes: '"the S-layer and outer membrane, but not the peptidoglycan layer and
        the cytoplasmic membrane, exhibited the polygonal shape"; negative boundary
        edge.'
curation_history:
- timestamp: '2026-05-05T01:35:46.901416+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-11T22:45:00-07:00'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added DOI-backed causal graph linking planar anisotropic envelope growth
    and S-layer constraints to triangular-shaped halophile morphology.
  llm_assisted: true
- timestamp: '2026-05-20T03:35:31Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×1).
  llm_assisted: true
- timestamp: '2026-05-23T21:30:07Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2007400×1).
  llm_assisted: true
- timestamp: '2026-05-24T04:13:19Z'
  curator: claude
  action: RENAME_PREDICATE_LABELS
  changes: 'Renamed 1 causal-edge predicate label(s) to align with existing groundings:
    shapes → causes ×1.'
  llm_assisted: true
- timestamp: '2026-05-24T04:13:22Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (biolink:causes×1).
  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: '2026-06-24T17:21:19Z'
  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