identifier: traitmech:000061
label: twitching motility
definition: A flagella-independent surface motility driven by the extension, attachment,
  and retraction of type IV pili, producing intermittent, jerky translocation of cells
  across moist surfaces.
definition_source: DOI:10.1146/annurev.micro.56.012302.160938
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000702
synonyms:
- synonym_text: twitching
  synonym_type: RELATED_SYNONYM
  source: DOI:10.1146/annurev.micro.56.012302.160938
evidence:
- reference: DOI:10.1146/annurev.micro.56.012302.160938
  notes: Mattick, "Type IV pili and twitching motility", describes twitching as type-IV-pilus-driven
    surface translocation operating like a grappling hook.
- reference: DOI:10.1146/annurev.micro.57.030502.091014
  notes: Harshey, "Bacterial motility on a surface", places twitching among the distinct
    surface-translocation strategies of bacteria.
canonical_examples:
- taxon_id: NCBITaxon:287
  taxon_label: Pseudomonas aeruginosa
  note: "Canonical type-IV-pilus twitching-motility model. Neisseria gonorrhoeae is a parallel model."
  reference: PMID:22746331
causal_graphs:
- graph_id: twitching_type_iv_pilus_retraction
  title: Twitching motility via type IV pilus extension and retraction
  description: Evidence-backed causal sketch linking type-IV-pilus dynamics (extension,
    surface attachment, retraction) to flagella-independent surface translocation.
  nodes:
  - node_id: twitching_trait
    label: twitching motility
    node_type: TRAIT
    grounding: traitmech:000061
    description: Flagella-independent surface motility on moist substrates.
  - node_id: type_iv_pilus
    label: type IV pilus
    node_type: CELLULAR_LOCALIZATION
    description: Surface filament that extends, attaches, and retracts to pull the
      cell forward.
    grounding: GO:0044096
  - node_id: pilus_assembly
    label: type IV pilus assembly
    node_type: BIOLOGICAL_PROCESS
    grounding: GO:0043107
    description: Polymerization and disassembly cycles driving pilus extension and
      retraction.
  - node_id: pilb_extension_atpase
    label: PilB extension ATPase
    node_type: GENE_OR_PROTEIN
    description: Cytoplasmic motor ATPase that powers type IV pilus filament extension.
  - node_id: pilt_retraction_atpase
    label: PilT retraction ATPase
    node_type: GENE_OR_PROTEIN
    description: Cytoplasmic motor ATPase that powers type IV pilus retraction.
  - node_id: pilus_extension
    label: type IV pilus extension
    node_type: BIOLOGICAL_PROCESS
    description: Polymerization of pilin subunits extending the pilus filament.
  - node_id: pilus_retraction
    label: type IV pilus retraction
    node_type: BIOLOGICAL_PROCESS
    description: Depolymerization of pilin subunits retracting the pilus and pulling
      the cell.
  - node_id: pilq_secretin
    label: PilQ secretin
    node_type: GENE_OR_PROTEIN
    description: Outer-membrane secretin channel through which the pilus filament
      is exposed to the cell surface.
  - node_id: pilus_filament_surface_exposure
    label: type IV pilus surface exposure
    node_type: BIOLOGICAL_PROCESS
    description: Exposure of the assembled pilus filament beyond the cell envelope
      to the external surface.
  - node_id: pilmnop_alignment_complex
    label: PilM/N/O/P alignment complex
    node_type: CELLULAR_LOCALIZATION
    description: Inner-membrane/periplasmic alignment subcomplex of the type IV pilus
      machine.
  - node_id: t4p_machine
    label: type IV pilus machine
    node_type: CELLULAR_LOCALIZATION
    description: Multiprotein nanomachine assembling, extending and retracting the
      type IV pilus.
  edges:
  - subject: type_iv_pilus
    predicate: enables
    object: twitching_trait
    description: Type IV pili are the molecular engines of twitching motility.
    evidence:
    - reference: DOI:10.1146/annurev.micro.56.012302.160938
      notes: Mattick describes twitching as type-IV-pilus-driven surface translocation.
    predicate_id: RO:0002327
  - subject: pilus_assembly
    predicate: enables
    object: twitching_trait
    description: Extension–attachment–retraction cycles pull the cell across the surface.
    evidence:
    - reference: DOI:10.1146/annurev.micro.57.030502.091014
      notes: Harshey treats twitching as a distinct surface-translocation strategy.
    predicate_id: RO:0002327
  - subject: pilb_extension_atpase
    predicate: drives
    object: pilus_extension
    description: PilB ATPase powers extension of the type IV pilus filament.
    evidence:
    - reference: DOI:10.1128/jb.00359-24
      notes: 'Roberge & Burrows 2024: "Extension is driven by PilB bound to PilC";
        T4P undergo cycles of extension/retraction powered by cytoplasmic motor ATPases.'
  - subject: pilt_retraction_atpase
    predicate: drives
    object: pilus_retraction
    description: PilT ATPase powers retraction of the type IV pilus filament.
    evidence:
    - reference: DOI:10.1128/jb.00359-24
      notes: 'Roberge & Burrows 2024: "Retraction is driven by PilT, which engages
        with PilC within the same cytoplasmic socket."'
  - subject: pilus_retraction
    predicate: enables
    object: twitching_trait
    description: Pilus retraction pulls the cell across the surface, producing twitching
      translocation.
    evidence:
    - reference: DOI:10.1128/jb.00442-23
      notes: 'Geiger et al. 2024: twitching is movement that pulls the cell across
        a surface through cooperative binding, pulling, and unbinding.'
    predicate_id: RO:0002327
  - subject: pilq_secretin
    predicate: enables surface exposure of
    object: pilus_filament_surface_exposure
    description: PilQ secretin is required for surface exposure of the assembled pilus
      filament.
    evidence:
    - reference: DOI:10.1099/mic.0.001311
      notes: 'Pelicic 2023: pilQ pilT mutants assemble filaments trapped in the periplasm,
        indicating PilQ is required for surface exposure.'
  - subject: pilmnop_alignment_complex
    predicate: part of
    object: t4p_machine
    description: The PilM/N/O/P alignment subcomplex is a structural part of the type
      IV pilus machine.
    evidence:
    - reference: DOI:10.1038/s41467-024-53638-y
      notes: 'Guo et al. 2024: the T4P machine includes an alignment subcomplex consisting
        of PilP, PilO, PilN, and PilM.'
    predicate_id: biolink:part_of
curation_history:
- timestamp: '2026-06-03T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate MORPHOLOGY/motility trait (twitching motility) under
    the existing motile class (METPO:1000702).
  llm_assisted: true
- timestamp: '2026-06-09T15:00:00Z'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added evidence-backed causal graph (type IV pilus retraction → twitching)
    with GO node grounding and RO predicate groundings; promoted PROPOSED to REVIEWED.
  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
    (GO:0044096×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 5 evidence-backed generic edges (8 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:14Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×1, biolink:part_of×1).
  llm_assisted: true