identifier: traitmech:000071 label: magnetosome definition: A membrane-bounded intracellular organelle containing a magnetic iron-mineral crystal (magnetite or greigite); chains of magnetosomes allow magnetotactic bacteria to align with and navigate along geomagnetic field lines. definition_source: DOI:10.1038/nrmicro.2016.99 trait_category: MORPHOLOGY term_kind: CLASS mapping_status: REVIEWED parent_traits: - traitmech:000066 synonyms: - synonym_text: magnetotactic synonym_type: RELATED_SYNONYM source: DOI:10.1038/nrmicro842 evidence: - reference: DOI:10.1038/nrmicro.2016.99 notes: Uebe & Schüler review magnetosome biogenesis as the formation of membrane-bounded magnetic-mineral organelles in magnetotactic bacteria. - reference: DOI:10.1038/nrmicro842 notes: Bazylinski & Frankel, "Magnetosome formation in prokaryotes", describe magnetosomes and the magnetotactic lifestyle they enable. canonical_examples: - taxon_id: NCBITaxon:431944 taxon_label: Magnetospirillum gryphiswaldense MSR-1 note: "Primary model for magnetosome biosynthesis (mamAB operon; MamK/MamJ-organised magnetite chains for magnetotaxis). AMB-1 (NCBITaxon:342108) is a co-equal model." reference: DOI:10.1038/s41579-025-01234-2 causal_graphs: - graph_id: magnetosome_magnetotaxis title: Magnetosome chains enable magnetotactic navigation description: Evidence-backed causal sketch linking membrane-bounded magnetic-mineral organelles arranged in chains to alignment with geomagnetic fields and magnetotactic navigation. nodes: - node_id: magnetosome_trait label: magnetosome node_type: TRAIT grounding: traitmech:000071 description: Membrane-bounded organelle containing a magnetic iron-mineral crystal. - node_id: magnetic_mineral_crystal label: magnetic iron-mineral crystal node_type: CHEMICAL description: Magnetite (Fe3O4) or greigite (Fe3S4) crystal inside the magnetosome. - node_id: magnetotaxis label: magnetotaxis node_type: BIOLOGICAL_PROCESS description: Movement biased along geomagnetic field lines. - node_id: mamk_protein label: MamK node_type: GENE_OR_PROTEIN description: Actin-like cytoskeletal protein that organizes magnetosomes into chains. - node_id: mamk_filaments label: actin-like MamK filaments node_type: CELLULAR_LOCALIZATION description: Long actin-like cytoskeletal filaments formed by MamK polymerization. - node_id: magnetosome_chain label: magnetosome chain assembly node_type: BIOLOGICAL_PROCESS description: Linear arrangement of magnetosomes into a chain acting as a cellular compass. - node_id: mamab_operon label: mamAB operon node_type: GENE_OR_PROTEIN description: Core magnetosome gene operon sufficient for rudimentary biomineralization. - node_id: biomineralization label: magnetosome biomineralization node_type: BIOLOGICAL_PROCESS description: Intracellular formation of the magnetic iron-mineral crystal. - node_id: mamb_protein label: MamB node_type: GENE_OR_PROTEIN description: Magnetosome membrane protein implicated in membrane invagination and crystal formation. grounding: UniProtKB:A0A6J4ZQS8 - node_id: membrane_invagination label: magnetosome membrane invagination node_type: BIOLOGICAL_PROCESS description: Invagination of the cytoplasmic membrane forming the magnetosome vesicle. - node_id: low_sulfide_environment label: oxygen-poor, low-sulfide environment node_type: ENVIRONMENTAL_FACTOR description: Habitat with low oxygen and low sulfide favoring magnetite mineralization. - node_id: magnetite_magnetosome label: magnetite magnetosome node_type: CHEMICAL description: Magnetosome containing a magnetite (Fe3O4) crystal. - node_id: sulfide_rich_habitat label: sulfide-rich habitat node_type: ENVIRONMENTAL_FACTOR description: Sulfide-rich habitat favoring greigite mineralization. - node_id: greigite_magnetosome label: greigite magnetosome node_type: CHEMICAL description: Magnetosome containing a greigite (Fe3S4) crystal. edges: - subject: magnetic_mineral_crystal predicate: located in object: magnetosome_trait description: The magnetic mineral crystal sits inside the magnetosome membrane. evidence: - reference: DOI:10.1038/nrmicro.2016.99 notes: Uebe & Schüler review magnetosome biogenesis as the formation of membrane-bounded magnetic-mineral organelles. predicate_id: biolink:located_in - subject: magnetosome_trait predicate: enables object: magnetotaxis description: Chains of magnetosomes act as a cellular compass, aligning the organism with geomagnetic field lines. evidence: - reference: DOI:10.1038/nrmicro842 notes: Bazylinski & Frankel describe magnetosomes and the magnetotactic lifestyle they enable. predicate_id: RO:0002327 - subject: mamk_protein predicate: organizes object: magnetosome_chain description: The actin-like protein MamK organizes magnetosomes into chains. evidence: - reference: DOI:10.1128/mbio.01649-23 notes: MTB align their magnetosome organelles into chains, organized by the actin-like MamK; broadly conserved. - subject: mamk_protein predicate: polymerizes into object: mamk_filaments description: MamK polymerizes into long actin-like filaments that scaffold the magnetosome chain. evidence: - reference: DOI:10.1128/mbio.01649-23 notes: MamK polymerizes into long, actin-like filaments. - subject: magnetosome_chain predicate: enables object: magnetotaxis description: Chain assembly of magnetosomes underlies the cellular compass enabling magnetotaxis. evidence: - reference: DOI:10.1128/mbio.01649-23 notes: Magnetosomes aligned into chains by MamK form the magnetic compass for navigation. predicate_id: RO:0002327 - subject: mamab_operon predicate: sufficient for object: biomineralization description: The mamAB operon is sufficient for rudimentary magnetosome biomineralization. evidence: - reference: DOI:10.1111/mmi.15330 notes: The mamAB operon is sufficient for rudimentary biomineralization. - subject: biomineralization predicate: produces object: magnetic_mineral_crystal description: Biomineralization forms the magnetic iron-mineral crystal within the magnetosome. evidence: - reference: DOI:10.1111/mmi.15330 notes: Magnetosome biomineralization yields the intracellular magnetic mineral crystal. predicate_id: METPO:2000202 - subject: mamb_protein predicate: promotes object: membrane_invagination description: MamB promotes invagination of the cytoplasmic membrane to form the magnetosome vesicle. evidence: - reference: DOI:10.1111/mmi.15330 notes: MamB likely recruits MAPs and promotes membrane invagination. predicate_id: RO:0002213 - subject: low_sulfide_environment predicate: favors object: magnetite_magnetosome description: Oxygen-poor, low-sulfide environments favor magnetite magnetosomes. evidence: - reference: DOI:10.1111/mmi.15330 notes: Magnetite is more common in oxygen-poor, low-sulfide environments. - subject: sulfide_rich_habitat predicate: favors object: greigite_magnetosome description: Sulfide-rich habitats favor greigite magnetosomes. evidence: - reference: DOI:10.1111/mmi.15330 notes: Greigite dominates in sulfide-rich habitats. curation_history: - timestamp: '2026-06-03T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate MORPHOLOGY trait (magnetosome); organelle sub-variant of intracellular inclusion. llm_assisted: true - timestamp: '2026-06-09T15:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (magnetosome / magnetotaxis) with 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 8 evidence-backed generic edges (11 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:13Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002327×1, METPO:2000202×1, RO:0002213×1). llm_assisted: true - timestamp: '2026-06-26T07:15:19Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:A0A6J4ZQS8×1). llm_assisted: true