identifier: METPO:1000671
label: diplococcus shaped
definition: A cell shape in which spherical cells remain attached in pairs following
  cell division, forming characteristic doublets.
definition_source: DOI:10.1038/ncomms4842
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000666
synonyms:
- synonym_text: diplococcus-shaped
  synonym_type: RELATED_SYNONYM
  source: metpo.owl
created_by: Luke Wang
evidence:
- reference: DOI:10.1038/ncomms4842
  snippet: Separation of daughter cells during bacterial cell division
  notes: Supports diplococcus-like paired morphology as linked to septal cross-wall
    splitting and daughter-cell separation.
canonical_examples:
- taxon_id: NCBITaxon:1313
  taxon_label: Streptococcus pneumoniae
  note: "Lancet-shaped diplococcus (paired cocci); the pneumococcus."
  reference: PMID:34779760
causal_graphs:
- graph_id: diplococcus_shaped_septal_separation
  title: Diplococcus paired-cell separation mechanism
  description: Evidence-backed causal sketch linking diplococcus morphology to septal
    peptidoglycan synthesis, peptidoglycan hydrolase-mediated cell separation, and
    retention of daughter-cell pairs.
  nodes:
  - node_id: diplococcus_shaped_trait
    label: diplococcus shaped
    node_type: TRAIT
    grounding: METPO:1000671
    description: Pair-forming spherical bacterial morphology.
  - node_id: septal_peptidoglycan_synthesis
    label: septal peptidoglycan synthesis
    node_type: BIOLOGICAL_PROCESS
    description: Division-associated wall synthesis at the septum.
  - node_id: septal_cross_wall
    label: septal cross wall
    node_type: CELLULAR_LOCALIZATION
    description: Peptidoglycan wall separating daughter cells.
  - node_id: pcsB_hydrolase_system
    label: PcsB hydrolase system
    node_type: GENE_OR_PROTEIN
    description: Pneumococcal cell-separation factor involved in cross-wall splitting.
  - node_id: daughter_cell_pair
    label: daughter-cell pair
    node_type: BIOLOGICAL_PROCESS
    description: Two cells remaining attached after division.
  - node_id: separation_pg_hydrolase
    label: septal peptidoglycan hydrolase
    node_type: GENE_OR_PROTEIN
    description: Cell-separation peptidoglycan hydrolase/autolysin dedicated to cleaving
      the septal cross-wall (e.g., LytB, AtlA, AmiC).
  - node_id: septum_cleavage
    label: septum cleavage
    node_type: BIOLOGICAL_PROCESS
    description: Enzymatic cleavage of septal peptidoglycan that resolves daughter
      cells.
  - node_id: hydrolase_septal_localization
    label: septal localization of separation hydrolase
    node_type: CELLULAR_LOCALIZATION
    description: Restricted targeting of the cell-separation autolysin to the division
      septum.
  - node_id: wall_teichoic_acid
    label: wall teichoic acid
    node_type: CHEMICAL
    description: Cell-wall teichoic acid polymer anchored to peptidoglycan; serves
      as recognition determinant for separation hydrolases.
  - node_id: lytr_lcp_enzyme
    label: LytR/LCP teichoic acid ligase
    node_type: GENE_OR_PROTEIN
    description: LCP-family enzyme that anchors wall teichoic acid precursor to peptidoglycan.
  - node_id: daughter_cell_separation
    label: daughter cell separation
    node_type: BIOLOGICAL_PROCESS
    description: Resolution of two daughter cells after division; incomplete separation
      retains paired cells.
    grounding: GO:0000920
  edges:
  - subject: septal_peptidoglycan_synthesis
    predicate: forms
    object: septal_cross_wall
    description: Septal wall synthesis forms the cross-wall between daughter cells.
    evidence:
    - reference: DOI:10.1016/j.cub.2021.04.041
      snippet: peptidoglycan assembly during the cell cycle
      notes: Supports septal PG assembly during ovococcal division.
    predicate_id: biolink:produces
  - subject: pcsB_hydrolase_system
    predicate: splits
    object: septal_cross_wall
    description: Cell separation requires splitting the septal cross-wall.
    evidence:
    - reference: DOI:10.1038/ncomms4842
      snippet: splitting of the septal cross wall
      notes: Supports PcsB-associated peptidoglycan hydrolase function in cell separation.
  - subject: septal_cross_wall
    predicate: incomplete separation yields
    object: daughter_cell_pair
    description: Incomplete or regulated separation of septal cross-wall material
      yields attached cell pairs.
    evidence:
    - reference: DOI:10.1128/JB.183.10.3108-3116.2001
      snippet: short chains with few or no free diplococci
      notes: Supports the relationship between pneumococcal separation state and diplococcus
        occurrence.
  - subject: daughter_cell_pair
    predicate: manifests as
    object: diplococcus_shaped_trait
    description: Attached daughter-cell pairs manifest the diplococcus-shaped trait.
    evidence:
    - reference: DOI:10.1038/ncomms4842
      snippet: daughter cells during bacterial cell division
      notes: Supports paired morphology as an outcome of daughter-cell separation
        dynamics.
    predicate_id: METPO:2007400
  - subject: separation_pg_hydrolase
    predicate: mediates
    object: septum_cleavage
    description: A dedicated peptidoglycan hydrolase mediates septum cleavage between
      daughter cells.
    evidence:
    - reference: DOI:10.1038/s42003-023-04808-z
      notes: Minimisation of cell chain size relies on a peptidoglycan hydrolase dedicated
        to septum cleavage (conserved separation-autolysin mechanism).
  - subject: septum_cleavage
    predicate: enables
    object: daughter_cell_separation
    description: Cleavage of the septal cross-wall enables resolution of daughter
      cells, favoring diplococci/short chains over long chains.
    evidence:
    - reference: DOI:10.1038/s42003-023-04808-z
      notes: Septum cleavage is the proximate process producing paired cells rather
        than long chains.
    predicate_id: RO:0002327
  - subject: hydrolase_septal_localization
    predicate: enables
    object: daughter_cell_separation
    description: Restricting the separation autolysin to the septum enables correct
      daughter-cell separation geometry.
    evidence:
    - reference: DOI:10.1038/s42003-023-04808-z
      notes: Restricted septal localization of the autolysin confines its lethal activity
        to its site of action, enabling separation; mislocalization yields chaining.
    predicate_id: RO:0002327
  - subject: wall_teichoic_acid
    predicate: promotes
    object: hydrolase_septal_localization
    description: Wall teichoic acid serves as a recognition determinant that promotes
      septal localization/binding of the separation hydrolase.
    evidence:
    - reference: DOI:10.1016/j.celrep.2023.112756
      notes: Separation-hydrolase binding is reduced in WTA-deficient cells but preserved
        in LTA-deficient cells; WTA acts as an envelope-polymer address for the autolysin.
    predicate_id: RO:0002213
  - subject: lytr_lcp_enzyme
    predicate: produces
    object: wall_teichoic_acid
    description: LytR/LCP-family ligase mediates the final step of wall teichoic acid
      formation and anchoring to peptidoglycan.
    evidence:
    - reference: DOI:10.1371/journal.pbio.3001990
      notes: LytR is the major enzyme mediating the final step in WTA formation, anchoring
        the TA precursor to PGN.
    predicate_id: METPO:2000202
  - subject: daughter_cell_separation
    predicate: incomplete separation yields
    object: daughter_cell_pair
    description: Incomplete daughter-cell separation retains attached cell pairs.
    evidence:
    - reference: DOI:10.1038/s42003-023-04808-z
      notes: Loss of septum-cleaving hydrolase activity shifts cells from separated/paired
        toward long chains; regulated separation yields paired cells.
curation_history:
- timestamp: '2026-05-05T01:35:46.887641+00:00'
  curator: seed_from_metpo
  action: SEEDED_FROM_METPO
  changes: imported from data/raw/metpo.owl (CLASS)
  llm_assisted: false
- timestamp: '2026-05-11T20:05:00-07:00'
  curator: codex
  action: CURATED_WITH_LITERATURE
  changes: Added DOI-backed definition and causal graph for septal peptidoglycan,
    PcsB-associated cross-wall splitting, daughter-cell pairing, and diplococcus morphology.
  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: '2026-06-13T21:03:26Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (biolink:produces×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 6 evidence-backed generic edges (6 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:0002327×2, RO:0002213×1, METPO:2000202×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:23:33Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (GO:0000920×1).
  llm_assisted: true