identifier: traitmech:000069
label: sulfur globule
definition: An intracellular (or periplasmic) inclusion of elemental sulfur formed
  as an intermediate during the oxidation of reduced sulfur compounds, characteristic
  of many sulfur-oxidizing and phototrophic sulfur bacteria.
definition_source: DOI:10.1016/S0065-2911(08)00002-7
trait_category: MORPHOLOGY
term_kind: CLASS
mapping_status: REVIEWED
parent_traits:
- traitmech:000066
synonyms:
- synonym_text: sulfur inclusion
  synonym_type: RELATED_SYNONYM
  source: DOI:10.1016/S0065-2911(08)00002-7
evidence:
- reference: DOI:10.1016/S0065-2911(08)00002-7
  notes: Frigaard & Dahl describe sulfur globules as sulfur-storage inclusions formed
    during oxidative sulfur metabolism in phototrophic sulfur bacteria.
- reference: DOI:10.1038/s41579-020-0413-0
  notes: Greening & Lithgow include sulfur globules among bacterial intracellular
    storage inclusions/organelles.
canonical_examples:
- taxon_id: NCBITaxon:90373
  taxon_label: Thiomargarita namibiensis
  note: "Giant sulfur bacterium storing conspicuous intracellular sulfur globules. Beggiatoa is a co-canonical exemplar."
  reference: PMID:10205058
causal_graphs:
- graph_id: sulfur_globule_sulfur_oxidation_intermediate
  title: Sulfur globules store elemental sulfur during oxidative sulfur metabolism
  description: Evidence-backed causal sketch linking oxidative sulfur metabolism to
    deposition of elemental sulfur as intracellular/periplasmic globules.
  nodes:
  - node_id: sulfur_globule_trait
    label: sulfur globule
    node_type: TRAIT
    grounding: traitmech:000069
    description: Intracellular / periplasmic inclusion of elemental sulfur.
  - node_id: elemental_sulfur
    label: elemental sulfur
    node_type: CHEMICAL
    description: S0 stored as a globule intermediate.
    grounding: CHEBI:26833
  - node_id: oxidative_sulfur_metabolism
    label: oxidative sulfur metabolism
    node_type: BIOLOGICAL_PROCESS
    description: Oxidation of reduced sulfur compounds (e.g. sulfide, thiosulfate).
  - node_id: sqr
    label: sulfide:quinone oxidoreductase (SQR)
    node_type: GENE_OR_PROTEIN
    description: Flavoenzyme that oxidizes sulfide, initiating intracellular sulfur
      oxidation.
  - node_id: sulfane_sulfur
    label: sulfane sulfur
    node_type: CHEMICAL
    description: Reactive zero-valent sulfur species produced during sulfide oxidation.
  - node_id: polysulfide
    label: polysulfide (H2Sn)
    node_type: CHEMICAL
    description: Short-chain inorganic polysulfide intermediate of sulfide oxidation.
  - node_id: persulfide_dioxygenase
    label: persulfide dioxygenase (PDO)
    node_type: GENE_OR_PROTEIN
    description: Enzyme oxidizing glutathione persulfide (GSSH) to sulfite.
  - node_id: sulfite
    label: sulfite
    node_type: CHEMICAL
    description: Oxidation product of glutathione persulfide via PDO.
  edges:
  - subject: oxidative_sulfur_metabolism
    predicate: produces
    object: elemental_sulfur
    description: Oxidation of reduced sulfur compounds generates elemental sulfur
      as an intermediate.
    evidence:
    - reference: DOI:10.1016/S0065-2911(08)00002-7
      notes: Frigaard & Dahl describe sulfur globules as sulfur-storage intermediates
        formed during oxidative sulfur metabolism.
    predicate_id: METPO:2000202
  - subject: elemental_sulfur
    predicate: located in
    object: sulfur_globule_trait
    description: The deposited elemental sulfur forms a globule inclusion.
    evidence:
    - reference: DOI:10.1038/s41579-020-0413-0
      notes: Greening & Lithgow include sulfur globules among bacterial intracellular
        storage inclusions.
    predicate_id: biolink:located_in
  - subject: sqr
    predicate: produces
    object: sulfane_sulfur
    description: SQR-catalyzed oxidation of sulfide generates sulfane sulfur intermediates.
    evidence:
    - reference: DOI:10.3390/ijms252010962
      notes: Initial oxidation of sulfide occurs under the action of SQR, producing
        sulfane sulfur; generalizes broadly to intracellular sulfur oxidizers.
    predicate_id: METPO:2000202
  - subject: sqr
    predicate: produces
    object: polysulfide
    description: SQR oxidizes sulfide to short-chain inorganic polysulfide (H2Sn,
      n>=2).
    evidence:
    - reference: DOI:10.1128/aem.01941-21
      notes: SQR oxidized H2S into short-chain inorganic polysulfide (H2Sn, n >= 2);
        broad sulfur-chemistry mechanism.
    predicate_id: METPO:2000202
  - subject: polysulfide
    predicate: precursor of
    object: sulfur_globule_trait
    description: Polysulfide/sulfane sulfur spontaneously generates S8 that aggregates
      into sulfur globules.
    evidence:
    - reference: DOI:10.1128/aem.01941-21
      notes: SQR oxidized H2S to H2Sn, which spontaneously generated S8; S8 aggregated
        into sulfur globules.
  - subject: persulfide_dioxygenase
    predicate: oxidizes
    object: sulfite
    description: PDO oxidizes glutathione persulfide (GSSH) to sulfite (GSSH + O2
      + H2O -> GSH + SO3^2- + 2H+).
    evidence:
    - reference: DOI:10.3390/ijms252010962
      notes: 'PDO acts on GSSH: GSSH + O2 + H2O -> GSH + SO3^2- + 2H+; well-defined
        enzymatic edge.'
    predicate_id: METPO:2000016
curation_history:
- timestamp: '2026-06-03T00:00:00Z'
  curator: claude
  action: PROPOSED_FROM_RESEARCH
  changes: Proposed candidate MORPHOLOGY trait (sulfur globule); storage 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 (oxidative sulfur metabolism → elemental
    sulfur globule) with METPO/biolink predicate groundings; promoted PROPOSED to
    REVIEWED.
  llm_assisted: true
- timestamp: '2026-06-14T05:51:46Z'
  curator: claude
  action: GROUND_CAUSAL_NODES
  changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv
    (CHEBI:26833×1).
  llm_assisted: true
- timestamp: '2026-06-23T00:00:00Z'
  curator: claude
  action: ENRICH_CAUSAL_GRAPH
  changes: Added 4 evidence-backed generic edges (5 new nodes) from the deep-research
    report.
  llm_assisted: true
- timestamp: '2026-06-24T17:21:14Z'
  curator: claude
  action: GROUND_CAUSAL_PREDICATES
  changes: Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv
    (METPO:2000202×2, METPO:2000016×1).
  llm_assisted: true