identifier: traitmech:000209 label: phage defense system definition: A genomics trait describing possession of one or more bacterial or archaeal immune systems that inhibit bacteriophage infection. definition_source: DOI:10.1038/s41579-019-0278-2 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - METPO:1000188 synonyms: - synonym_text: antiphage defense system synonym_type: EXACT_SYNONYM source: DOI:10.1126/science.aar4120 - synonym_text: anti-phage system synonym_type: EXACT_SYNONYM source: DOI:10.1038/s41586-019-1894-8 - synonym_text: pan-immune system synonym_type: RELATED_SYNONYM source: DOI:10.1038/s41579-019-0278-2 evidence: - reference: DOI:10.1038/s41579-019-0278-2 snippet: Viruses and their hosts are engaged in a constant arms race leading to the evolution of antiviral defence mechanisms notes: Bernheim and Sorek define the bacterial bacteriophage-defense context and review the pan-genomic diversity and cost of antiviral defense systems. - reference: DOI:10.1038/s41579-019-0278-2 snippet: individual microorganisms often encode multiple distinct defence systems notes: The pan-immune-system model supports treating possession of one or more defense systems as a strain-level genomics trait rather than a single protein, locus, or pathway. - reference: DOI:10.1038/s41586-019-1894-8 snippet: Bacteria have evolved numerous immune mechanisms, both innate and adaptive notes: Hampton et al. review innate and adaptive anti-phage systems and the phage counter-defense mechanisms that evade them. - reference: DOI:10.1038/s41586-019-1894-8 snippet: Here we review the spectrum of anti-phage systems and highlight their evasion by bacteriophages notes: This supports the umbrella scope spanning diverse CRISPR-Cas, restriction-modification, BREX, DISARM, abortive-infection, and related anti-phage defenses. - reference: DOI:10.1126/science.aar4120 snippet: Candidate immune systems were then experimentally validated for their activities notes: The Science article summary for Doron et al. supports genomic discovery and experimental validation of antiphage defense systems from microbial pangenomes. canonical_examples: - taxon_id: NCBITaxon:1308 taxon_label: Streptococcus thermophilus note: S. thermophilus is the organism in which CRISPR-Cas adaptive immunity was experimentally shown to provide phage resistance. reference: DOI:10.1126/science.1138140 causal_graphs: - graph_id: phage_defense_system_hierarchy title: Antiphage defense systems resist viral challenge description: Evidence-backed ontology sketch linking phage pressure to the umbrella phage-defense-system trait and its reviewed CRISPR-Cas and restriction-modification children. scope_status: NONMECHANISTIC scope_notes: This parent trait groups independently reviewed genome-level anti-phage defense systems without claiming that CRISPR-Cas, restriction-modification, BREX, DISARM, abortive infection, or other defense families share one universal molecular mechanism. nodes: - node_id: bacteriophage_pressure label: bacteriophage pressure node_type: ENVIRONMENTAL_FACTOR description: Selective pressure imposed by bacteriophage infection. - node_id: phage_defense_system_trait label: phage defense system node_type: TRAIT grounding: traitmech:000209 description: Possession of one or more genome-encoded immune systems that inhibit bacteriophage infection. - node_id: crispr_cas_system label: CRISPR-Cas system node_type: TRAIT grounding: traitmech:000094 description: Adaptive immune system using CRISPR arrays and Cas proteins to recognize invading nucleic acids. - node_id: restriction_modification_system label: restriction-modification system node_type: TRAIT grounding: traitmech:000095 description: Paired methyltransferase and restriction-endonuclease system for self/non-self DNA discrimination. edges: - subject: bacteriophage_pressure predicate: selects for predicate_id: METPO:2007401 object: phage_defense_system_trait description: Virus-host arms races select for microbial antiviral defense mechanisms. evidence: - reference: DOI:10.1038/s41579-019-0278-2 snippet: constant arms race leading to the evolution of antiviral defence mechanisms notes: Bernheim and Sorek frame bacteriophages and bacterial hosts as engaged in an evolutionary arms race. - subject: crispr_cas_system predicate: is a predicate_id: rdfs:subClassOf object: phage_defense_system_trait description: CRISPR-Cas possession is an adaptive phage-defense system. evidence: - reference: DOI:10.1126/science.aar4120 snippet: well-known defense arsenals such as restriction-modification and CRISPR systems notes: The Science article summary for Doron et al. places CRISPR systems among the recognized microbial defense arsenals. - subject: restriction_modification_system predicate: is a predicate_id: rdfs:subClassOf object: phage_defense_system_trait description: Restriction-modification possession is an innate phage-defense system. evidence: - reference: DOI:10.1126/science.aar4120 snippet: well-known defense arsenals such as restriction-modification and CRISPR systems notes: The Science article summary for Doron et al. places restriction-modification systems among the recognized microbial defense arsenals. discussions: - discussion_id: phage-defense-system-xref-gap prompt: Resolve exact ontology xrefs for organism-level phage defense system possession before adding TraitRecord xrefs. kind: CURATION_TODO status: OPEN rationale: The pinned METPO snapshot retains only obsolete phage defense, and GO:0051607 defense response to virus is a biological process rather than this GENOMICS possession trait. CRISPR-Cas, restriction-modification, BREX, DISARM, abortive-infection, and other mechanism terms are narrower than the umbrella parent curated here. posed_by: codex posed_date: '2026-09-15' curation_history: - timestamp: '2026-09-15T07:55:00Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted phage defense system as a DOI-backed GENOMICS TraitRecord after an ignored-and-hidden duplicate review found only obsolete METPO phage defense and future-gap mentions; the replacement placeholder is reserved in proposals/metpo_traitmech_v86. llm_assisted: true