identifier: traitmech:000101 label: rRNA operon copy number definition: A quantitative genomics property describing the number of ribosomal RNA (rrn) operons encoded in a genome, which correlates with maximal growth rate and ecological strategy. definition_source: DOI:10.1128/AEM.66.4.1328-1333.2000 trait_category: GENOMICS term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000188 synonyms: - synonym_text: rrn copy number synonym_type: RELATED_SYNONYM source: DOI:10.1128/AEM.66.4.1328-1333.2000 evidence: - reference: DOI:10.1128/AEM.66.4.1328-1333.2000 notes: Klappenbach, Dunbar & Schmidt show rRNA operon copy number reflects ecological strategies, with fast responders carrying more copies. - reference: DOI:10.1038/nmicrobiol.2016.160 notes: Roller, Stoddard & Schmidt link rrn copy number to bacterial growth rate and growth efficiency. canonical_examples: - taxon_id: NCBITaxon:691 taxon_label: Vibrio natriegens note: "high rRNA-operon copy number (fast growth)" reference: PMID:23969053 - taxon_id: NCBITaxon:562 taxon_label: Escherichia coli note: "seven rRNA operons" reference: PMID:15528533 causal_graphs: - graph_id: rrn_copy_growth_rate title: rRNA operon copy number sets ribosome biogenesis and growth rate description: Evidence-backed causal sketch linking rrn copy number to ribosome biogenesis capacity and maximal growth rate. nodes: - node_id: rrna_copy_trait label: rRNA operon copy number node_type: TRAIT grounding: traitmech:000101 description: Number of rrn operons encoded per genome. - node_id: ribosome_biogenesis label: ribosome biogenesis node_type: BIOLOGICAL_PROCESS grounding: GO:0042254 description: Assembly of ribosomal RNA and proteins into functional ribosomes. - node_id: maximal_growth_rate label: maximal growth rate node_type: QUALITY description: Upper bound on per-cell exponential growth rate. - node_id: rrna_transcription label: rRNA transcription node_type: BIOLOGICAL_PROCESS description: Synthesis of ribosomal RNA from rrn operons by RNA polymerase. grounding: GO:0009303 - node_id: growth_efficiency label: growth efficiency node_type: QUALITY description: Carbon/substrate use efficiency of biomass production. - node_id: chemotactic_motility label: chemotactic motility node_type: BIOLOGICAL_PROCESS description: Directed cell movement in response to chemical gradients. - node_id: genome_size label: genome size node_type: QUALITY description: Total genome length of an organism. edges: - subject: rrna_copy_trait predicate: enables object: ribosome_biogenesis description: Higher rrn copy number raises rRNA transcription capacity for ribosome assembly. evidence: - reference: DOI:10.1128/AEM.66.4.1328-1333.2000 notes: Klappenbach et al. tie rrn copy number to copiotrophic strategies with fast ribosome assembly. predicate_id: RO:0002327 - subject: rrna_copy_trait predicate: associated with object: maximal_growth_rate description: rrn copy number correlates with maximal growth rate across bacteria. evidence: - reference: DOI:10.1038/nmicrobiol.2016.160 notes: Roller et al. link rrn copy number to bacterial growth rate and growth efficiency. predicate_id: biolink:associated_with - subject: rrna_copy_trait predicate: increases capacity for object: rrna_transcription description: Multiple rrn operons increase capacity to raise rRNA transcription and ribosome synthesis rapidly. evidence: - reference: DOI:10.1128/AEM.66.4.1328-1333.2000 notes: rrn transcription can account for up to ~70% of cellular transcription during rapid growth; multiple operons increase ability to raise ribosome synthesis rapidly. - subject: rrna_copy_trait predicate: decreases object: growth_efficiency description: Higher rrn copy number is associated with lower growth (carbon use) efficiency. evidence: - reference: DOI:10.1038/nmicrobiol.2016.160 notes: 'Roller et al.: growth efficiency is inversely related to maximal growth rate and rrn copy number.' predicate_id: RO:0002212 - subject: rrna_copy_trait predicate: positively associated with object: chemotactic_motility description: Higher rrn copy number is associated with greater probability of chemotactic motility across genomes. evidence: - reference: DOI:10.1038/nmicrobiol.2016.160 notes: Chemotactic motility shows a positive relationship with log2-rrn (up to +41.25% non-phylogenetic, +10.60% phylogenetic) across 1,167 genomes. - subject: rrna_copy_trait predicate: positively correlates with object: genome_size description: rrn copy number positively correlates with genome size across bacteria. evidence: - reference: DOI:10.1038/nmicrobiol.2016.160 notes: Genome size and rrn copy number show a positive logarithmic relationship; ~+0.66 Mbp phylogenetically for 15 vs 1 rrn. curation_history: - timestamp: '2026-06-05T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate GENOMICS trait (rRNA operon copy number) from literature research. llm_assisted: true - timestamp: '2026-06-08T14:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (rrn copy / ribosome biogenesis / growth rate) with GO node grounding and RO/biolink predicate groundings; promoted PROPOSED to REVIEWED. llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 4 evidence-backed generic edges (4 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:11Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002212×1). 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 (GO:0009303×1). llm_assisted: true