magnetosome

GO:0110143 · Membrane organelle · Membrane bounded organelle · Proposed

A membrane-bounded organelle of magnetotactic bacteria enclosing a nanocrystal of a magnetic iron mineral — magnetite (Fe3O4) or greigite (Fe3S4). Magnetosomes are invaginations of the cytoplasmic membrane that are filled with iron, and are arranged into a chain along a cytoskeletal filament so that the cell behaves as a swimming compass needle. [GO:0110143]

Xrefs: uniprot.location:SL-0510 — Magnetosome MICRO:0000216 — magnetosome

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
magnetosome membrane	Lipid	part of			ESSENTIAL	Invagination of the cytoplasmic membrane that encloses the mineral crystal and carries the Mam proteins. `DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 review magnetosome membrane invagination as the first step of biogenesis.
magnetosome membrane proteins (Mam/Mms)	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	mamA, mamB, mamE, mamM, mamO, mms6	ESSENTIAL	Encoded by the magnetosome gene island; control membrane invagination, iron transport, and crystal nucleation and size. `DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 describe the mam and mms genes of the magnetosome island and their roles in biogenesis. `DOI:10.1002/pro.2827` Barber-Zucker & Zarivach 2015 survey the magnetosome-associated proteins and their assigned roles.
magnetite	Small molecule	part of	`CHEBI:46726`		ESSENTIAL	The magnetic mineral core (Fe3O4), biomineralised to a species-specific size and habit within the vesicle. Some lineages make greigite (Fe3S4, CHEBI:86238) instead. `DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 describe magnetite (and greigite) biomineralisation inside the magnetosome vesicle.
MamK filament	Protein complex	acts on	`cellstructuremech:mamk_filament`	mamK	DISPENSABLE	Cytoskeletal filament that aligns assembled magnetosomes into a chain. Machinery acting on the assembled organelle rather than a constituent of it: vesicles still form and mineralise without the filament, but they scatter. `DOI:10.1038/nrmicro.2016.99` Uebe and Schuler 2016 describe MamK filaments arranging magnetosomes in a chain. `DOI:10.1002/pro.2827` Barber-Zucker and Zarivach 2015 describe MamK as the actin-like filament associated with magnetosome chains.
MamJ connector	Protein	acts on	`InterPro:IPR060787`	mamJ	DISPENSABLE	Acidic connector that links magnetosome vesicles to MamK filaments. `DOI:10.1038/nrmicro.2016.99` Uebe and Schuler 2016 review MamJ as a connector between magnetosome vesicles and MamK filaments. `DOI:10.1002/pro.2827` Barber-Zucker and Zarivach 2015 describe MamJ connecting magnetosome membranes to the MamK filament.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

magnetosome membrane proteins (Mam/Mms)

Accession	Protein	Gene	Organism	Entry
`UniProtKB:Q93DY9`	Magnetosome protein MamA	mamA	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (2 references) The single reviewed UniProtKB entry for gene mamA in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:11571158` Grünberg K et al. 2001, ‘A large gene cluster encoding several magnetosome proteins is conserved in different species of magnetotactic bacteria.’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of Q93DY9. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of Q93DY9.
`UniProtKB:V6F510`	Magnetosome protein MamB	mamB	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (3 references) The single reviewed UniProtKB entry for gene mamB in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:11571158` Grünberg K et al. 2001, ‘A large gene cluster encoding several magnetosome proteins is conserved in different species of magnetotactic bacteria.’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F510. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F510. `PMID:22007638` Uebe R et al. 2011, ‘The cation diffusion facilitator proteins MamB and MamM of Magnetospirillum gryphiswaldense have distinct and complex functions, and are involved in magnetite biomineralization and magnetosome membrane assembly.’, Mol Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F510.
`UniProtKB:V6F2B6`	Magnetosome formation protease MamE	mamE	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (2 references) The single reviewed UniProtKB entry for gene mamE in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:11571158` Grünberg K et al. 2001, ‘A large gene cluster encoding several magnetosome proteins is conserved in different species of magnetotactic bacteria.’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F2B6. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F2B6.
`UniProtKB:V6F235`	Magnetosome protein MamM	mamM	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (2 references) The single reviewed UniProtKB entry for gene mamM in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F235. `PMID:22007638` Uebe R et al. 2011, ‘The cation diffusion facilitator proteins MamB and MamM of Magnetospirillum gryphiswaldense have distinct and complex functions, and are involved in magnetite biomineralization and magnetosome membrane assembly.’, Mol Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of V6F235.
`UniProtKB:Q93DZ1`	Probable membrane transporter protein MamO	mamO	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene mamO in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of Q93DZ1.
`UniProtKB:Q6NE76`	Magnetite biomineralization protein Mms6	mms6	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (1 reference) The single reviewed UniProtKB entry for gene mms6 in Magnetospirillum gryphiswaldense MSR-1, a taxon this record names. Identifier for the component's declared gene symbol; it is not itself evidence that the protein is part of this structure. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence cited by UniProt for the 'Magnetosome membrane' localisation of Q6NE76.

MamJ connector

Accession	Protein	Gene	Organism	Entry
`UniProtKB:V6F519`	Magnetosome-associated protein MamJ	mamJ	Magnetospirillum gryphiswaldense MSR-1 (`NCBITaxon:431944`)	REVIEWED
Role and evidence (1 reference) Reviewed MSR-1 MamJ accession for the acidic connector that links magnetosome vesicles to MamK filaments. `PMID:14766587` Grünberg K et al. 2004, ‘Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense’, Appl Environ Microbiol. ECO:0000269 experimental evidence for the magnetosome localisation of V6F519, as cited by UniProt.
`UniProtKB:Q2W8Q7`	Magnetosome-associated protein MamJ	mamJ	Paramagnetospirillum magneticum AMB-1 (`NCBITaxon:342108`)	REVIEWED
Role and evidence (2 references) Reviewed AMB-1 MamJ accession for the acidic connector that links magnetosome vesicles to MamK filaments. `PMID:20212111` Murat D et al. 2010, ‘Comprehensive genetic dissection of the magnetosome gene island reveals the step-wise assembly of a prokaryotic organelle.’, Proc Natl Acad Sci U S A. ECO:0000269 experimental evidence for the magnetosome localisation of Q2W8Q7, as cited by UniProt. `PMID:27481925` Arakaki A et al. 2016, ‘Comparative Subcellular Localization Analysis of Magnetosome Proteins Reveals a Unique Localization Behavior of Mms6 Protein onto Magnetite Crystals.’, J Bacteriol. ECO:0000269 experimental evidence for the magnetosome localisation of Q2W8Q7, as cited by UniProt.

Taxonomic distribution

NCBITaxon:28211 Alphaproteobacteria — VARIABLE: Magnetotaxis is confined to particular lineages; the cultured models are here. [DOI:10.1038/nrmicro.2016.99]
NCBITaxon:1236 Gammaproteobacteria — RARE: Magnetotactic representatives are known but few. [DOI:10.1038/nrmicro.2016.99]
NCBITaxon:2157 Archaea — ABSENT: No magnetotactic archaeon has been described. [DOI:10.1038/nrmicro.2016.99]

Canonical examples

NCBITaxon:431944 Magnetospirillum gryphiswaldense MSR-1 — The genetic model for magnetosome biogenesis. [DOI:10.1038/nrmicro.2016.99]
NCBITaxon:342108 Paramagnetospirillum magneticum AMB-1 — The second cultured model; source of much of the cell-biological work. [DOI:10.1038/nrmicro.2016.99]

Functions

magnetoreception — The magnetosome chain gives the cell a permanent magnetic dipole, so it aligns passively with the geomagnetic field while swimming.
- DOI:10.1038/nrmicro.2016.99 Uebe & Schüler 2016 describe the chain as a compass needle aligning the cell with the geomagnetic field.

Associated traits

CONFERS traitmech:000071 — magnetosome magnetosome
- DOI:10.1038/nrmicro.2016.99 Uebe & Schuler 2016 describe the magnetosome as the structure whose possession defines the magnetotactic phenotype TraitMech records as traitmech:000071.

Physical properties

DIAMETER: 35-120 UO:0000018 (magnetite crystal, species-dependent) [DOI:10.1038/nrmicro.2016.99]

Mechanism graphs

Membrane invagination, mineralisation and chain assembly make the cell a compass (ASSEMBLY)

Subject	Predicate	Object	Evidence
Mam proteins	forms	magnetosome membrane	`DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016: magnetosome membrane invagination is protein-directed.
Mam proteins	transports	iron atom	`DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 describe MamB/MamM-type transporters supplying iron.
iron atom	is mineralised into	magnetite	`DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 describe magnetite biomineralisation within the vesicle.
MamK filament	aligns	magnetosome chain	`DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016: MamK/MamJ organise the chain; mamJ deletion scatters magnetosomes.
magnetosome chain	produces	cellular magnetic dipole	`DOI:10.1038/nrmicro.2016.99` Uebe & Schüler 2016 describe the chain's summed magnetic moment orienting the cell.

Discussions

CURATION_TODO (OPEN): Add a micrograph whose imaged organism is identified to species. Commons carries CC BY 3.0 TEM images of magnetosome chains from Pósfai et al. (PMC3840360), but their captions identify the cells only as 'magnetotactic Alphaproteobacteria' or an unnamed strain, and the schema requires an image taxon the record already claims.
KNOWLEDGE_GAP (OPEN): Most magnetosome proteins carry no experimental evidence for their magnetosome localisation in UniProt. Seeding UniProt SL-0510 for Magnetospirillum gryphiswaldense MSR-1 returned 27 reviewed proteins; only MamJ carries an ECO:0000269 PubMed citation for the localisation itself, so only it produced a protein example. The rest are annotated by rule or similarity. That is a statement about the annotation, not about the biology — but it means per-protein localisation evidence has to come from the primary literature rather than from UniProt.

Evidence

DOI:10.1038/nrmicro.2016.99 Uebe R & Schüler D 2016, 'Magnetosome biogenesis in magnetotactic bacteria', Nature Reviews Microbiology.
DOI:10.1002/pro.2827 Barber-Zucker & Zarivach 2015, 'From invagination to navigation: the story of magnetosome-associated proteins', Protein Science — independent review of the magnetosome protein complement and chain assembly.

Curation history

2026-08-31T03:48:12Z claude · CREATED_RECORD — Drafted from the cited review. Every GO term, taxon id and DOI was resolved against OLS, NCBI Taxonomy and Crossref before writing; evidence notes state what the review says, not a reading of primary literature. Not yet human-reviewed.
2026-08-31T03:48:24Z uniprot_sl · ADD_UNIPROT_SL_XREF — Added uniprot.location:SL-0510 (Magnetosome); mapping read from the GO line of UniProt subcell.txt.
2026-08-31T03:49:12Z uniprot_sl · SEED_PROTEIN_EXAMPLES — Added 1 taxon-paired protein example(s) from UniProtKB reviewed entries annotated to SL-0510 (Magnetosome), matched to components by gene symbol, each carrying UniProt's ECO:0000269 PubMed evidence for the localisation.
2026-08-31T03:49:13Z claude · NOTE_EVIDENCE_GAP — Recorded that only 1 of 27 reviewed MSR-1 magnetosome proteins carries experimental localisation evidence in UniProt.
2026-08-31T03:50:27Z claude · FIX_ID_LABEL_FINDINGS — id-label gate: CHEBI:50290 was written from memory for magnetite and resolves to 'sapphyrin PCI-2052'; replaced with the verified CHEBI:46726 magnetite. Node labels aligned to the ontology labels (magnetite, iron atom).
2026-08-31T03:54:23Z claude · ADD_CORROBORATION — Added an independent second review (#63) and the parent_structures link to intracellular membrane-bounded organelle (#64).
2026-08-31T04:08:43Z claude · ADD_TRAIT_EVIDENCE — TraitLink.evidence became required in the schema; cited the review already backing the record for the magnetosome trait link.
2026-08-31T06:02:12Z claude · APPLY_COMPONENT_BOUNDARY — Component-boundary rule (#66): MamK/MamJ is machinery acting on the assembled magnetosome, so its essentiality moves from CONDITIONAL to DISPENSABLE — the organelle forms without it.
2026-08-31T06:12:34Z claude · SET_COMPONENT_ROLE — component_role became required (#77) so the constituent/machinery distinction is machine-readable rather than prose. Set per component; ASSOCIATED_MACHINERY only where the protein acts on the already-assembled structure.
2026-09-01T20:52:03Z micro_xrefs · ADD_XREF — Added MICRO:0000216 (magnetosome) as a curator-reviewed identity xref; exact non-obsolete MicrO id and label verified through OLS.
2026-09-02T05:45:20Z interpro_groundings · GROUND_COMPONENTS — Applied exact integrated InterPro family groundings to none; recorded label-only decisions for mamk_filament. The fixed reviewed allow-list required exact component identity, reviewed UniProt examples, type=family entries, and unchanged family consensus across curated scope examples.
2026-09-02T23:27:21Z uniprot_sl · ENRICH_EVIDENCE_NOTES — #41: added the cited paper's author, year, title and journal to 1 UniProt-seeded evidence note(s), fetched from PubMed esummary. The notes were previously identical per accession, so a reader could not tell the cited papers apart. Only notes byte-identical to the seeded boilerplate were touched.
2026-09-04T01:40:08Z codex · ENHANCE_CAUSAL_GRAPH — Added the missing description to the magnetosome iron-mineralisation edge.
2026-09-08T07:38:17Z uniprot_sl · SEED_PROTEIN_EXAMPLES — Added 1 taxon-paired protein example(s) from UniProtKB reviewed entries annotated to SL-0510 (Magnetosome), matched to components by gene symbol, each carrying UniProt's ECO:0000269 PubMed evidence for the localisation.
2026-09-08T07:39:32Z uniprot_genes · SEED_PROTEIN_EXAMPLES — #183: added 7 protein example(s) by resolving each of the component's declared gene symbols to the single reviewed UniProtKB entry for that symbol in a taxon this record names, deduplicated by accession. Symbols resolving to more than one reviewed entry were skipped rather than chosen between.
2026-09-13T08:10:42Z codex · GROUND_MAMK_FILAMENT — Split the combined MamK/MamJ associated-machinery component so the MamK filament now grounds to cellstructuremech:mamk_filament while MamJ remains a reviewed label-only connector component.
2026-09-13T08:12:26Z codex · GROUND_MAMJ_CONNECTOR — Grounded the split MamJ connector component to the exact InterPro MamJ family and narrowed its protein-example roles to the connector component.

Source: data/structures/membrane_organelle/magnetosome.yaml