identifier: traitmech:000102
label: pangenome openness
definition: A genomics trait describing the structure of a species' pangenome — the
  balance of core versus accessory genes and whether the pangenome is open (continually
  acquiring new genes across genomes) or closed.
definition_source: DOI:10.1073/pnas.0506758102
trait_category: GENOMICS
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000188
synonyms:
- synonym_text: open pangenome
  synonym_type: NARROW_SYNONYM
  source: DOI:10.1073/pnas.0506758102
evidence:
- reference: DOI:10.1073/pnas.0506758102
  notes: Tettelin et al. introduced the microbial pan-genome concept, distinguishing
    core and dispensable genes and open versus closed pangenomes.
- reference: DOI:10.1038/nmicrobiol.2017.40
  notes: McInerney, McNally & O'Connell review why prokaryotes have pangenomes and
    what drives their openness.
canonical_examples:
- taxon_id: NCBITaxon:562
  taxon_label: Escherichia coli
  note: "Textbook open pan-genome: enormous accessory-genome diversity across strains relative to the core genome."
  reference: PMID:20623278
causal_graphs:
- graph_id: pangenome_openness_hgt
  title: Horizontal gene transfer drives open pangenomes
  description: Evidence-backed causal sketch linking HGT and ecological breadth to
    open versus closed pangenome structure.
  nodes:
  - node_id: pangenome_openness_trait
    label: pangenome openness
    node_type: TRAIT
    grounding: traitmech:000102
    description: Open versus closed structure of a species' pangenome.
  - node_id: horizontal_gene_transfer
    label: horizontal gene transfer
    node_type: BIOLOGICAL_PROCESS
    description: Acquisition of genes between lineages outside vertical descent.
    grounding: GO:0009292
  - node_id: accessory_gene_pool
    label: accessory gene pool
    node_type: QUALITY
    description: Strain-variable genes outside the species core.
  - node_id: plasmid
    label: plasmid
    node_type: GENE_OR_PROTEIN
    description: Mobile genetic element acting as a vehicle for accessory genes.
  - node_id: prophage
    label: prophage
    node_type: GENE_OR_PROTEIN
    description: Integrated bacteriophage genome contributing to gene flux.
  - node_id: gene_gain_loss_dynamics
    label: gene gain and loss dynamics
    node_type: BIOLOGICAL_PROCESS
    description: Ongoing acquisition and loss of genes across sampled lineages.
  - node_id: core_gene_fraction
    label: core gene fraction
    node_type: QUALITY
    description: Proportion of genes conserved across all genomes in the species.
  - node_id: rare_gene_fraction
    label: rare gene fraction
    node_type: QUALITY
    description: Proportion of genes present in only a few genomes.
  - node_id: sampling_bias
    label: sampling bias
    node_type: EXPERIMENTAL_FACTOR
    description: Bias in which genomes are sampled, distorting openness estimates.
  - node_id: annotation_error
    label: annotation error
    node_type: EXPERIMENTAL_FACTOR
    description: Misannotation of genes that distorts presence/absence calls.
  - node_id: apparent_pangenome_openness
    label: apparent pangenome openness
    node_type: QUALITY
    description: Estimated openness that may reflect artifacts rather than true HGT
      dynamics.
  edges:
  - subject: horizontal_gene_transfer
    predicate: causes
    object: pangenome_openness_trait
    description: HGT continually adds new accessory genes, keeping the pangenome open.
    evidence:
    - reference: DOI:10.1073/pnas.0506758102
      notes: Tettelin et al. introduce the pan-genome concept distinguishing open
        vs closed pangenomes.
    predicate_id: biolink:causes
  - subject: pangenome_openness_trait
    predicate: associated with
    object: accessory_gene_pool
    description: Open pangenomes accumulate large accessory gene pools across strains.
    evidence:
    - reference: DOI:10.1038/nmicrobiol.2017.40
      notes: McInerney et al. review the ecological and population drivers of pangenome
        openness.
    predicate_id: biolink:associated_with
  - subject: plasmid
    predicate: enables
    object: horizontal_gene_transfer
    description: Plasmids are mobile vehicles for accessory genes, increasing opportunity
      for gene acquisition.
    evidence:
    - reference: DOI:10.1099/mgen.0.001021
      notes: Gene gain and loss mediated by mobile genetic elements including plasmids.
    predicate_id: RO:0002327
  - subject: prophage
    predicate: promotes
    object: pangenome_openness_trait
    description: Prophage-associated gene flux contributes to recent gain/loss and
      accessory genome expansion.
    evidence:
    - reference: DOI:10.3390/microorganisms12050986
      notes: Prophages, integrases, and transfer/mobile elements identified as main
        drivers of pangenome openness.
    predicate_id: RO:0002213
  - subject: gene_gain_loss_dynamics
    predicate: shapes
    object: pangenome_openness_trait
    description: Open/closed behavior reflects balance of ongoing gene gain versus
      loss across sampled lineages.
    evidence:
    - reference: DOI:10.1101/2022.04.23.489244
      notes: HGT and resultant gene gain and loss dynamics are central drivers of
        pangenome composition.
  - subject: core_gene_fraction
    predicate: negatively associated with
    object: pangenome_openness_trait
    description: A larger conserved core leaves less flexible accessory fraction;
      empirically anticorrelated with openness.
    evidence:
    - reference: DOI:10.3390/microorganisms12050986
      notes: Strong inverse correlation between core gene percentage and openness
        coefficient (corr = -0.910).
  - subject: rare_gene_fraction
    predicate: positively associated with
    object: pangenome_openness_trait
    description: A higher proportion of rare genes indicates continued acquisition
      and non-saturation of the pangenome.
    evidence:
    - reference: DOI:10.3390/microorganisms12050986
      notes: Positive correlation between rare gene percentage and openness coefficient
        (corr = 0.742).
  - subject: sampling_bias
    predicate: biases estimate of
    object: apparent_pangenome_openness
    description: Apparent openness can reflect which genomes were sampled rather than
      true HGT dynamics.
    evidence:
    - reference: DOI:10.1101/2022.04.23.489244
      notes: Gene accumulation curves can be misleading because they may reflect sampling
        temporal/diversity bias.
  - subject: annotation_error
    predicate: biases estimate of
    object: apparent_pangenome_openness
    description: Misannotation inflates or deflates presence/absence calls and can
      misclassify open/closed status.
    evidence:
    - reference: DOI:10.1101/2022.04.23.489244
      notes: Higher rates of annotation error can lead to incorrect estimates of whether
        a pangenome is open or closed.
curation_history:
- timestamp: '2026-06-05T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate GENOMICS trait (pangenome openness) from literature
    research.
  llm_assisted: true
- timestamp: '2026-06-08T14:00:00Z'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added evidence-backed causal graph (HGT-driven open pangenome) with biolink
    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:0009292×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 7 evidence-backed generic edges (8 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:11Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002327×1, RO:0002213×1).
  llm_assisted: true