identifier: traitmech:000528
label: cellular buoyancy
definition: A physiology trait in which intracellular gas vesicles reduce a microbial
  cell's effective density enough to provide buoyancy and vertical positioning in
  the water column.
definition_source: DOI:10.1186/s13036-024-00426-3
trait_category: PHYSIOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000059
synonyms:
- synonym_text: buoyancy
  synonym_type: RELATED_SYNONYM
  source: DOI:10.1186/s13036-024-00426-3
evidence:
- reference: DOI:10.1186/s13036-024-00426-3
  snippet: can provide buoyancy for them to move up and down the water to obtain nutrients
  notes: Feng et al. review gas-vesicle physical properties that provide buoyancy
    for photosynthetic bacteria and halophilic archaea.
- reference: DOI:10.1186/s13036-024-00426-3
  snippet: give them the buoyancy to move upward so that they can get enough light
    for photosynthesis
  notes: Feng et al. describe gas vesicles giving photosynthetic bacteria buoyancy
    to move upward toward sufficient light.
- reference: DOI:10.3390/life12091455
  snippet: Approximately 3–10% of the cell volume must be occupied by gas vesicles
    to provide buoyancy
  notes: Pfeifer reviews gas-vesicle proteins and summarizes the fraction of cell
    volume that must contain gas vesicles to confer buoyancy.
canonical_examples:
- taxon_id: NCBITaxon:1126
  taxon_label: Microcystis aeruginosa
  note: Mlouka et al. mapped the M. aeruginosa gas-vesicle gene cluster and DNA rearrangements
    that lead to loss of cellular buoyancy.
  reference: DOI:10.1128/JB.186.8.2355-2365.2004
causal_graphs:
- graph_id: gas_vesicles_confer_cellular_buoyancy
  title: Gas vesicles confer cellular buoyancy
  description: Evidence-backed causal sketch linking a proteinaceous gas-filled organelle
    to cellular buoyancy.
  scope_status: NONMECHANISTIC
  scope_notes: The graph records the organelle-scale physical gas-vesicle branch and
    leaves taxon-specific Gvp protein assembly to the gas-vesicle morphology record.
    It does not assert that all planktonic depth regulation is gas-vesicle mediated.
  nodes:
  - node_id: gas_vesicle_shell
    label: gas vesicle shell
    node_type: CELLULAR_LOCALIZATION
    description: Proteinaceous shell enclosing the gas-vesicle lumen.
    grounding: GO:0033172
  - node_id: gas_vesicle
    label: gas vesicle
    node_type: ORGANELLE
    description: Hollow gas-filled protein nanocompartment that displaces cytoplasmic
      volume.
    grounding: GO:0031411
  - node_id: cellular_buoyancy_trait
    label: cellular buoyancy
    node_type: TRAIT
    description: Gas-vesicle-mediated capacity for upward flotation or water-column
      positioning.
    grounding: traitmech:000528
  edges:
  - subject: gas_vesicle_shell
    predicate: part of
    predicate_id: biolink:part_of
    object: gas_vesicle
    description: The protein shell encloses the internal gas volume as part of the
      gas vesicle.
    evidence:
    - reference: DOI:10.1186/s13036-024-00426-3
      snippet: The gas vesicle (GV) is like a hollow nanoparticle consisting of an
        internal gas and a protein shell
      notes: Feng et al. describe the gas vesicle as an internal gas compartment bounded
        by a protein shell.
  - subject: gas_vesicle
    predicate: confers
    predicate_id: METPO:2007700
    object: cellular_buoyancy_trait
    description: Gas-filled vesicles lower effective cellular density and provide
      buoyancy.
    evidence:
    - reference: DOI:10.1186/s13036-024-00426-3
      snippet: can provide buoyancy for them to move up and down the water to obtain
        nutrients
      notes: Feng et al. review gas-vesicle physical properties that provide buoyancy
        for photosynthetic bacteria and halophilic archaea.
    - reference: DOI:10.1186/s13036-024-00426-3
      snippet: give them the buoyancy to move upward so that they can get enough light
        for photosynthesis
      notes: Feng et al. describe gas vesicles giving photosynthetic bacteria buoyancy
        to move upward toward sufficient light.
discussions:
- discussion_id: cellular-buoyancy-xref-gap
  prompt: Resolve exact external ontology xrefs for gas-vesicle-mediated cellular
    buoyancy.
  kind: CURATION_TODO
  status: OPEN
  rationale: No exact active local METPO class was accepted for the organism-level
    cellular-buoyancy physiology trait. The only buoyancy hit in the local METPO snapshot
    is obsolete buoyancy structure, and GO:0031411 denotes the gas vesicle organelle
    rather than the gas-vesicle-conferred physiological disposition.
  posed_by: codex
  posed_date: '2026-10-01'
curation_history:
- timestamp: '2026-10-01T22:49:00Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Minted cellular buoyancy as a DOI-backed PHYSIOLOGY TraitRecord after an
    ignored-and-hidden duplicate review found no exact same-scope TraitMech, METPO,
    history, or prior proposal record; the replacement placeholder is reserved in
    proposals/metpo_traitmech_v405.
  llm_assisted: true