identifier: traitmech:000223 label: SspABCD-SspFGH system definition: A phosphorothioate defense system in which an organism possesses an SspABCD-SspFGH locus that pairs an SspABCD-family single-stranded DNA phosphorothioation module with an SspFGH restriction module to damage non-phosphorothioated phage DNA and suppress phage DNA replication. definition_source: DOI:10.1128/mbio.00613-21 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000213 synonyms: - synonym_text: SspABCD-SspFGH defense system synonym_type: EXACT_SYNONYM source: DOI:10.1128/mbio.00613-21 evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: new type of ssDNA PT-based SspABCD-SspFGH defense system capable of providing protection against phages notes: Wang et al. name SspABCD-SspFGH as a single-stranded DNA phosphorothioation-based bacterial phage-defense system. - reference: DOI:10.1128/mbio.00613-21 snippet: PT-modifying genes sspBCD and iscS in Vibrio anguillarum strain FF-93 can provide protection against a range of phages in combination with sspFGH notes: Wang et al. support a native Vibrio anguillarum FF-93 Ssp system whose IscS-SspBCD phosphorothioation module works with the sspFGH cassette. - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH coupled with IscS-SspBCD behaves as a new type of ssDNA PT modification-based defense barrier to fend off phage invasion notes: Wang et al. support the modification-plus-restriction architecture and antiphage output. - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH damages non-PT-modified DNA and exerts antiphage activity by suppressing phage DNA replication notes: Wang et al. connect SspFGH-dependent DNA damage to the observed block in phage DNA replication. - reference: DOI:10.1038/s41564-020-0700-6 snippet: SspABCD confers single-stranded and high-frequency PTs with SspB acting as a nickase notes: Xiong et al. independently support SspABCD-family single-stranded host-DNA phosphorothioation. - reference: DOI:10.3390/ijms252413316 snippet: could also be coupled to SspFGH for anti-phage activity notes: Xu and Gu summarize SspFGH as an SspABCD-coupled phosphorothioate antiphage restriction module. canonical_examples: - taxon_id: NCBITaxon:55601 taxon_label: Vibrio anguillarum note: Wang et al. identified an sspFGH cassette adjacent to the sspBCD cluster in Vibrio anguillarum FF-93 and showed that its SspFGH module couples to IscS-SspBCD phosphorothioation for phage defense. reference: DOI:10.1128/mbio.00613-21 causal_graphs: - graph_id: sspabcd_sspfgh_non_pt_dna_damage title: SspABCD-SspFGH systems couple Ssp PT marks to foreign-DNA damage description: Evidence-backed process sketch linking an SspABCD-SspFGH locus to single-stranded host DNA phosphorothioation, SspFGH-dependent damage of non-phosphorothioated phage DNA, and reduced phage DNA replication. scope_status: NONMECHANISTIC scope_notes: The graph captures SspABCD-SspFGH restriction at the system level without asserting one universal host taxon, PT frequency, a DNA-damage chemistry, a complete SspFGH subunit cycle, or relationship to SspE and archaeal PT antiviral systems. nodes: - node_id: sspabcd_sspfgh_locus label: SspABCD-SspFGH locus node_type: GENETIC_ELEMENT description: An Ssp phosphorothioation-dependent restriction locus pairing an SspABCD-family DNA modification module with SspFGH restriction activity. - node_id: ssp_single_stranded_dna_phosphorothioation label: Ssp single-stranded DNA phosphorothioation node_type: BIOLOGICAL_PROCESS description: SspABCD-family installation of single-stranded phosphorothioate marks on host DNA. - node_id: ssp_pt_self_nonself_discrimination label: Ssp PT self/nonself discrimination node_type: BIOLOGICAL_PROCESS description: Use of Ssp phosphorothioate marks to distinguish phosphorothioated host DNA from invading DNA that lacks host phosphorothioate marks. - node_id: sspfgh_non_pt_dna_damage label: SspFGH-dependent non-PT DNA damage node_type: BIOLOGICAL_PROCESS description: SspFGH-dependent damage of DNA molecules that lack host single-stranded phosphorothioate marks. - node_id: phage_dna_replication label: phage DNA replication node_type: BIOLOGICAL_PROCESS description: Replication of invading bacteriophage DNA after host cell entry. - node_id: sspabcd_sspfgh_system_trait label: SspABCD-SspFGH system node_type: TRAIT grounding: traitmech:000223 description: Possession of a genome-encoded SspABCD-SspFGH restriction-modification defense system. - node_id: phosphorothioate_defense_system_trait label: phosphorothioate defense system node_type: TRAIT grounding: traitmech:000213 description: Possession of a genome-encoded phosphorothioate-based phage defense system. edges: - subject: sspabcd_sspfgh_locus predicate: contributes to predicate_id: RO:0002326 object: ssp_single_stranded_dna_phosphorothioation description: The SspABCD-family modification module installs single-stranded PT marks on host DNA. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: IscS and SspBCD in FF-93 also confer DNA PT modification at 5'-CPSCA-3' consensus sequences notes: Wang et al. support single-stranded host-DNA phosphorothioation by the FF-93 IscS-SspBCD module. - subject: sspabcd_sspfgh_locus predicate: contributes to predicate_id: RO:0002326 object: sspfgh_non_pt_dna_damage description: SspABCD-SspFGH loci pair the Ssp modification module with SspFGH-dependent restriction activity against DNA lacking PT marks. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH coupled with IscS-SspBCD behaves as a new type of ssDNA PT modification-based defense barrier notes: Wang et al. support the paired Ssp phosphorothioation and SspFGH restriction architecture. - subject: ssp_single_stranded_dna_phosphorothioation predicate: contributes to predicate_id: RO:0002326 object: ssp_pt_self_nonself_discrimination description: SspFGH uses Ssp phosphorothioate marks as a recognition tag to discriminate self DNA from invading non-PT DNA. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH employs ssDNA PT modification as a recognition tag to introduce damage to non-PT-modified phage genomes notes: Wang et al. support PT-dependent self/nonself discrimination by the SspFGH barrier. - subject: ssp_pt_self_nonself_discrimination predicate: activates predicate_id: RO:0002213 object: sspfgh_non_pt_dna_damage description: Ssp PT self/nonself discrimination leads to SspFGH-dependent damage of non-PT phage DNA. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH introduces damage to non-PT DNA and consequently impairs phage DNA replication notes: Wang et al. connect SspFGH non-PT DNA damage to the restriction output. - subject: sspfgh_non_pt_dna_damage predicate: mitigates predicate_id: METPO:2007407 object: phage_dna_replication description: SspFGH-dependent damage of phage DNA suppresses phage DNA replication. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: its DNA replication was markedly suppressed in the presence of IscS-SspBCD-SspFGH notes: Wang et al. directly connect the SspFGH barrier to impaired phage DNA replication. - subject: sspfgh_non_pt_dna_damage predicate: confers predicate_id: METPO:2007700 object: sspabcd_sspfgh_system_trait description: SspFGH-dependent non-PT DNA damage realizes the SspABCD-SspFGH antiphage defense trait. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: SspFGH provided moderate levels of protection against phages notes: Wang et al. support phage restriction as the SspFGH system output. - subject: sspabcd_sspfgh_system_trait predicate: is a predicate_id: rdfs:subClassOf object: phosphorothioate_defense_system_trait description: SspABCD-SspFGH possession is a phosphorothioate-defense-system trait. evidence: - reference: DOI:10.1128/mbio.00613-21 snippet: new type of ssDNA PT-based SspABCD-SspFGH defense system notes: Wang et al. place SspABCD-SspFGH among single-stranded DNA phosphorothioation-based defense systems. curation_history: - timestamp: '2026-09-15T17:06:06Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted SspABCD-SspFGH system as a DOI-backed GENOMICS TraitRecord under the phosphorothioate defense system parent after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v100. llm_assisted: true