identifier: traitmech:000098
label: genome size
definition: A quantitative genomics property describing the total length of an organism's
  genome (typically expressed in megabase pairs), which varies widely across prokaryotes
  and reflects lifestyle and evolutionary forces.
definition_source: DOI:10.1038/nrmicro3331
trait_category: GENOMICS
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- METPO:1000188
synonyms:
- synonym_text: genome length
  synonym_type: RELATED_SYNONYM
  source: DOI:10.1038/nrmicro3331
evidence:
- reference: DOI:10.1038/nrmicro3331
  notes: Batut et al. review reductive genome evolution, linking genome size to population
    size and lifestyle across prokaryotes.
- reference: DOI:10.1038/ismej.2014.60
  notes: Giovannoni et al. discuss streamlining theory and the small genomes of abundant
    free-living microbes.
causal_graphs:
- graph_id: genome_size_population_lifestyle
  title: Genome size reflects effective population size and lifestyle
  description: Evidence-backed causal sketch linking effective population size and
    lifestyle to reductive evolution shaping prokaryotic genome length.
  nodes:
  - node_id: genome_size_trait
    label: genome size
    node_type: TRAIT
    grounding: traitmech:000098
    description: Total genomic length of an organism.
  - node_id: effective_population_size
    label: effective population size
    node_type: ENVIRONMENTAL_FACTOR
    description: Long-term breeding population size shaping selection efficiency.
  - node_id: reductive_genome_evolution
    label: reductive genome evolution
    node_type: BIOLOGICAL_PROCESS
    description: Selective and drift-driven loss of genomic content.
    grounding: METPO:1007721
  - node_id: ocean_depth
    label: ocean depth
    node_type: ENVIRONMENTAL_FACTOR
    description: Depth layer in the marine water column (epipelagic to bathypelagic).
  - node_id: soil_ph
    label: soil pH
    node_type: ENVIRONMENTAL_FACTOR
    description: Acidity/alkalinity of soil habitat.
    grounding: ENVO:09200010
  - node_id: horizontal_gene_transfer
    label: horizontal gene transfer
    node_type: BIOLOGICAL_PROCESS
    description: Acquisition of genetic material between organisms, expanding gene
      content.
    grounding: GO:0009292
  - node_id: mobile_genetic_elements
    label: mobile genetic elements
    node_type: CHEMICAL
    description: Plasmids, phages, ICEs, transposons and insertion sequences that
      move DNA between genomes.
  - node_id: gene_loss
    label: gene loss
    node_type: BIOLOGICAL_PROCESS
    description: Loss of protein-coding genes leading to genome reduction.
  - node_id: metabolic_versatility
    label: metabolic versatility
    node_type: CAPACITY
    description: Breadth of metabolic functions encoded by a genome.
  edges:
  - subject: effective_population_size
    predicate: regulates
    object: reductive_genome_evolution
    description: Large Ne strengthens selection against superfluous DNA; small Ne
      permits drift-driven loss in symbionts.
    evidence:
    - reference: DOI:10.1038/nrmicro3331
      notes: Batut et al. compare reductive genome evolution at both ends of the population-size
        spectrum.
    predicate_id: RO:0002211
  - subject: reductive_genome_evolution
    predicate: causes
    object: genome_size_trait
    description: Reductive evolution sets the observed genome length.
    evidence:
    - reference: DOI:10.1038/ismej.2014.60
      notes: Giovannoni et al. link streamlining theory to small genomes in abundant
        free-living microbes.
    predicate_id: biolink:causes
  - subject: ocean_depth
    predicate: positively associated with
    object: genome_size_trait
    description: Average genome size of marine communities increases with ocean depth.
    evidence:
    - reference: DOI:10.1038/s41467-023-36988-x
      notes: 'Ngugi 2023: AGS increases with depth across epipelagic, mesopelagic
        and bathypelagic metagenomes.'
  - subject: soil_ph
    predicate: negatively associated with
    object: genome_size_trait
    description: Low-pH soils host communities with larger average genomes.
    evidence:
    - reference: DOI:10.1101/2021.11.17.469016
      notes: 'Chuckran 2023: negative AGS-pH relationship in soil; strengthened after
        microbial-DNA correction (R2 0.32->0.57).'
  - subject: horizontal_gene_transfer
    predicate: increases
    object: genome_size_trait
    description: HGT is a driving force behind genome expansion, adding accessory
      gene content.
    evidence:
    - reference: DOI:10.1038/s41559-024-02357-0
      notes: 'Dmitrijeva 2024: HGT described as driving force behind genome expansion;
        ~42.5% of genes affected by HGT per species.'
    predicate_id: RO:0002213
  - subject: mobile_genetic_elements
    predicate: mediates
    object: horizontal_gene_transfer
    description: MGEs (plasmids, phages, ICEs, transposons, insertion sequences) carry
      out HGT.
    evidence:
    - reference: DOI:10.1111/1462-2920.16630
      notes: 'Kogay 2024: MGEs crucial for horizontal gene transfer, including plasmids,
        ICEs, transposons, IS and phages.'
  - subject: gene_loss
    predicate: decreases
    object: genome_size_trait
    description: Loss of protein-coding genes reduces genome length.
    evidence:
    - reference: DOI:10.1038/s41467-024-50368-z
      notes: 'Dong 2024: KO-abundance changes track genome size, indicating protein-coding
        gene loss and genome reduction.'
    predicate_id: RO:0002212
  - subject: metabolic_versatility
    predicate: positively associated with
    object: genome_size_trait
    description: Greater metabolic versatility is correlated with larger genomes.
    evidence:
    - reference: DOI:10.1038/s41564-023-01465-0
      notes: 'Piton 2023: soil bacterial trait axis of metabolic versatility strongly
        positively correlated with genome size (R2=0.64).'
curation_history:
- timestamp: '2026-06-05T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate GENOMICS trait (genome size) from literature research.
  llm_assisted: true
- timestamp: '2026-06-08T14:00:00Z'
  curator: claude
  action: CURATED_CAUSAL_GRAPH
  changes: Added evidence-backed causal graph (genome size / population-size and lifestyle)
    with RO/biolink predicate groundings; promoted PROPOSED to REVIEWED.
  llm_assisted: true
- timestamp: '2026-06-16T06:54:40Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (METPO:1007721×1).
  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: '2026-06-24T17:21:11Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (RO:0002213×1, RO:0002212×1).
  llm_assisted: true
- timestamp: '2026-06-24T17:21:18Z'
  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: '2026-06-24T17:23:32Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (ENVO:09200010×1).
  llm_assisted: true