identifier: traitmech:000368 label: MqsRAC system definition: A phage defense system in which an organism possesses a tripartite MqsRAC toxin-antitoxin-chaperone locus represented by DefenseFinder as a two-profile model requiring MqsRAC__mqsC and MqsRAC__mqsR. definition_source: DOI:10.1128/spectrum.03388-23 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000209 synonyms: - synonym_text: MqsRAC synonym_type: RELATED_SYNONYM source: DOI:10.1128/spectrum.03388-23 - synonym_text: MqsR/MqsA/MqsC synonym_type: RELATED_SYNONYM source: DOI:10.1128/spectrum.03388-23 - synonym_text: MqsRAC__mqsC synonym_type: RELATED_SYNONYM source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md - synonym_text: MqsRAC__mqsR synonym_type: RELATED_SYNONYM source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md evidence: - reference: PMID:38054715 snippet: Therefore, our results are important since we show for the first time that a phage-defense system, the MqsRAC toxin/antitoxin system, allows the host to survive infection by forming persister cells, rather than inducing cell suicide. notes: Fernandez-Garcia et al. support MqsRAC as a phage-defense system whose outcome is host survival through persister-cell formation rather than cell suicide. - reference: PMID:38054715 snippet: Moreover, we demonstrate that the MqsRAC system works in concert with restriction/modification systems. notes: Fernandez-Garcia et al. connect the MqsRAC system to restriction/modification systems during phage inhibition. - reference: DOI:10.1128/spectrum.03388-23 snippet: the tripartite system MqsR (RNase toxin)/MqsA (antitoxin)/MqsC (SecB-type chaperone) notes: Fernandez-Garcia et al. describe MqsR/MqsA/MqsC as a tripartite toxin-antitoxin-chaperone phage-exclusion system from Escherichia coli C496_10. - reference: DOI:10.1128/spectrum.03388-23 snippet: We found there was a 2,100 to a 5,000-fold reduction in the EOP with phage T2 when the cells produced MqsR/MqsA/MqsC notes: Fernandez-Garcia et al. support MqsRAC-mediated reduction of T2 efficiency of plating. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: MqsRAC | 10\.1101/2022\.05\.12\.491691 | Mapping the landscape of anti-phage defense mechanisms in the E\. coli pangenome notes: The DefenseFinder article registry maps the named MqsRAC system to Vassallo et al.'s E. coli pangenome phage-defense screen. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "MqsRAC\tMqsRAC\t2\t2\tMqsRAC__mqsC, MqsRAC__mqsR\t\t\t" notes: The DefenseFinder rules table models MqsRAC as a two-profile system requiring the MqsRAC__mqsC and MqsRAC__mqsR profiles. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| MqsRAC__mqsC | MqsRAC__mqsC | MqsRAC | Custom | 20 |' notes: The DefenseFinder HMM inventory records MqsRAC__mqsC under MqsRAC. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| MqsRAC__mqsR | MqsRAC__mqsR | MqsRAC | Custom | 20 |' notes: The DefenseFinder HMM inventory records MqsRAC__mqsR under MqsRAC. causal_graphs: - graph_id: mqsrac_locus_promotes_persister_phage_defense title: MqsRAC loci support T2 phage inhibition description: Conservative system-level sketch linking possession of an MqsRAC locus to persister-cell formation and T2 inhibition without asserting a universal phage trigger, lethal abortive-infection route, or exact MqsRAC profile-to-activity mapping. scope_status: NONMECHANISTIC scope_notes: The graph captures MqsRAC as a named DefenseFinder two-profile phage-defense system while leaving natural phage breadth, upstream MqsRAC activation logic, the exact relationship between the two DefenseFinder profiles and the tripartite MqsR/MqsA/MqsC locus, and cooperating restriction/modification contexts unresolved. nodes: - node_id: mqsrac_locus label: MqsRAC locus node_type: GENETIC_ELEMENT description: A toxin-antitoxin-chaperone locus represented by DefenseFinder MqsRAC__mqsC and MqsRAC__mqsR profiles. - node_id: mqsrac_persister_formation label: MqsRAC-dependent persister cell formation node_type: BIOLOGICAL_PROCESS description: Formation of persister cells during T2 phage attack in cells producing MqsR/MqsA/MqsC. - node_id: rm_assisted_t2_inhibition label: restriction/modification-assisted T2 inhibition node_type: BIOLOGICAL_PROCESS description: Inhibition of T2 phage by MqsR/MqsA/MqsC in concert with restriction/modification systems. - node_id: mqsrac_system_trait label: MqsRAC system node_type: TRAIT grounding: traitmech:000368 description: Possession of a genome-encoded MqsRAC toxin-antitoxin-chaperone phage-defense system. - node_id: phage_defense_system label: phage defense system node_type: TRAIT grounding: traitmech:000209 description: Possession of one or more genome-encoded immune systems that inhibit bacteriophage infection. edges: - subject: mqsrac_locus predicate: contributes to predicate_id: RO:0002326 object: mqsrac_persister_formation description: Fernandez-Garcia et al. show that the MqsR/MqsA/MqsC toxin-antitoxin-chaperone system can promote persister-cell formation during T2 attack, and DefenseFinder models MqsRAC as a two-profile system. evidence: - reference: PMID:38054715 snippet: Therefore, our results are important since we show for the first time that a phage-defense system, the MqsRAC toxin/antitoxin system, allows the host to survive infection by forming persister cells, rather than inducing cell suicide. notes: Fernandez-Garcia et al. connect the MqsRAC system to persister-cell formation. - reference: DOI:10.1128/spectrum.03388-23 snippet: the tripartite system MqsR (RNase toxin)/MqsA (antitoxin)/MqsC (SecB-type chaperone) notes: Fernandez-Garcia et al. identify the system components as MqsR, MqsA, and MqsC. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: MqsRAC | 10\.1101/2022\.05\.12\.491691 | Mapping the landscape of anti-phage defense mechanisms in the E\. coli pangenome notes: The DefenseFinder article registry maps the named MqsRAC system to Vassallo et al.'s E. coli pangenome phage-defense screen. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "MqsRAC\tMqsRAC\t2\t2\tMqsRAC__mqsC, MqsRAC__mqsR\t\t\t" notes: The DefenseFinder rules table models MqsRAC as a two-profile system requiring the MqsRAC__mqsC and MqsRAC__mqsR profiles. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| MqsRAC__mqsC | MqsRAC__mqsC | MqsRAC | Custom | 20 |' notes: The DefenseFinder HMM inventory records MqsRAC__mqsC under MqsRAC. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| MqsRAC__mqsR | MqsRAC__mqsR | MqsRAC | Custom | 20 |' notes: The DefenseFinder HMM inventory records MqsRAC__mqsR under MqsRAC. - subject: mqsrac_locus predicate: contributes to predicate_id: RO:0002326 object: rm_assisted_t2_inhibition description: Fernandez-Garcia et al. report that the MqsR/MqsA/MqsC toxin-antitoxin-chaperone system works in concert with restriction/modification systems during T2 inhibition. evidence: - reference: DOI:10.1128/spectrum.03388-23 snippet: Therefore, MqsR/MqsA/MqsC works in concert with restriction/modification systems to inhibit T2 phage. notes: Fernandez-Garcia et al. connect the MqsRAC system to restriction/modification activity during T2 inhibition. - subject: mqsrac_persister_formation predicate: confers predicate_id: METPO:2007700 object: mqsrac_system_trait description: MqsRAC-dependent survival through persister-cell formation realizes the MqsRAC system trait. evidence: - reference: PMID:38054715 snippet: Therefore, our results are important since we show for the first time that a phage-defense system, the MqsRAC toxin/antitoxin system, allows the host to survive infection by forming persister cells, rather than inducing cell suicide. notes: Fernandez-Garcia et al. report MqsRAC-dependent host survival through persister-cell formation rather than cell suicide. - subject: rm_assisted_t2_inhibition predicate: confers predicate_id: METPO:2007700 object: mqsrac_system_trait description: MqsR/MqsA/MqsC-mediated T2 inhibition realizes the MqsRAC system trait. evidence: - reference: DOI:10.1128/spectrum.03388-23 snippet: We found there was a 2,100 to a 5,000-fold reduction in the EOP with phage T2 when the cells produced MqsR/MqsA/MqsC notes: Fernandez-Garcia et al. report reduced T2 efficiency of plating in cells producing MqsR/MqsA/MqsC. - subject: mqsrac_system_trait predicate: is a predicate_id: rdfs:subClassOf object: phage_defense_system description: MqsRAC system possession is a phage-defense-system trait. evidence: - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: MqsRAC | 10\.1101/2022\.05\.12\.491691 | Mapping the landscape of anti-phage defense mechanisms in the E\. coli pangenome notes: The DefenseFinder article registry maps the named MqsRAC system to Vassallo et al.'s E. coli pangenome phage-defense screen. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "MqsRAC\tMqsRAC\t2\t2\tMqsRAC__mqsC, MqsRAC__mqsR\t\t\t" notes: The DefenseFinder rules table models MqsRAC as a two-profile system requiring the MqsRAC__mqsC and MqsRAC__mqsR profiles. discussions: - discussion_id: mqsrac-breadth-and-profile-gap prompt: Resolve MqsRAC natural phage breadth, phage-activation signals, the exact DefenseFinder profile-to-MqsR/MqsA/MqsC relationship, and cooperating restriction/modification contexts before minting narrower MqsRAC mechanism children. kind: KNOWLEDGE_GAP status: OPEN rationale: Fernandez-Garcia et al. support MqsR/MqsA/MqsC as an Escherichia coli C496_10 toxin-antitoxin-chaperone system that inhibits T2 phage through persister-cell formation and in concert with restriction/modification systems, while DefenseFinder models MqsRAC through MqsRAC__mqsC and MqsRAC__mqsR markers. Natural phage breadth, the phage signal that activates MqsRAC, MqsA coverage in the DefenseFinder model, and cooperating restriction/modification contexts remain unresolved. evidence: - reference: PMID:38054715 snippet: Moreover, we demonstrate that the MqsRAC system works in concert with restriction/modification systems. notes: Fernandez-Garcia et al. leave the MqsRAC and restriction/modification connection at system-level resolution. attaches_to: - causal_graphs#mqsrac_locus_promotes_persister_phage_defense posed_by: codex posed_date: '2026-09-22' curation_history: - timestamp: '2026-09-22T15:02:00Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted MqsRAC system as a DOI-backed GENOMICS TraitRecord under phage defense system after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, history, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v245. llm_assisted: true - timestamp: '2026-09-22T15:03:00Z' curator: codex action: REVIEW_CANONICAL_EXAMPLE_EVIDENCE_GAP changes: 'Reviewed the MqsRAC canonical_examples gap and left canonical_examples empty: the current evidence supports a MqsR/MqsA/MqsC system from Escherichia coli C496_10 expressed from its natural promoter in a K-12 host, but it does not cite a directly observed natural microbial taxon broad enough for a canonical example of endogenous MqsRAC system possession. No paid research was used.' llm_assisted: true - timestamp: '2026-09-22T15:15:00Z' curator: codex action: GRAPH_EDGE_DIRECTION_REVIEW changes: 'Addressed issue #1258 by replacing the unsupported MqsRAC persister-cell formation to restriction/modification-assisted T2 inhibition edge with independent MqsRAC locus to restriction/modification-assisted T2 inhibition and MqsRAC-dependent persister formation to MqsRAC system trait edges.' llm_assisted: true - timestamp: '2026-09-22T15:18:00Z' curator: codex action: REVIEW_RESTRICTION_MODIFICATION_SPECIFICITY changes: 'Addressed issue #1259 by generalizing unsupported McrBC-specific wording to restriction/modification-assisted T2 inhibition throughout the MqsRAC graph and discussion.' llm_assisted: true