identifier: traitmech:000705
label: aerobic overflow metabolism
definition: A physiological phenotype in which microbial cells divert part of their
  catabolic carbon flux to excreted, incompletely oxidized products with lower ATP
  yield per substrate than complete respiration, despite possessing respiratory capacity
  and sufficient oxygen for respiration.
definition_source: DOI:10.1038/msb.2009.82
trait_category: PHYSIOLOGY
term_kind: CLASS
mapping_status: PROPOSED
parent_traits:
- METPO:1000059
evidence:
- reference: DOI:10.1038/msb.2009.82
  snippet: S. cerevisiae and E. coli fully oxidize glucose at low concentrations and
    shift to overflow metabolism at high glucose concentrations.
  notes: Molenaar et al. 2009, PMID:19888218, PMC2795476; Current growth models and
    their limitations, not the abstract. The surrounding paragraph supplies the fully
    aerobic, incomplete-oxidation and retained respiratory-capacity differentia. This
    Perspective contains original modeling, not new experimental replication of the
    cited organisms. The terminology discussion also includes mixed-acid-to-lactate
    shifts; the qualified label here does not define every use of unqualified overflow
    metabolism.
- reference: DOI:10.1038/nature15765
  snippet: cells use fermentation instead of the more efficient respiration to generate
    energy, despite the availability of oxygen.
  notes: Basan et al. 2015, PMID:26632588, PMC4843128; scientific abstract. Relevant
    Results, growth Methods, model scope, Extended Data Table 1, actual Figure 1 and
    Extended Data Figure 2 were inspected through public XML and figure assets. Acetate
    excretion depends on growth conditions; the fitted threshold is not universal.
    The oxidative-fermentation accounting includes oxygen-dependent NADH oxidation.
    Net excretion does not exclude acetate reuptake. Proteome allocation is a tested
    model in this system, not a necessary mechanism for every member of the trait.
    Complete supplements, equations and referenced batch-culture methods were not
    independently reanalyzed. Publisher retrieval failed; the public full-text XML
    was accessible.
- reference: DOI:10.1111/febs.13019
  snippet: All fermenting yeasts exhibited significant ethanol formation within the
    first 20 min in response to a glucose pulse
  notes: Hagman et al. 2014, PMID:25161062, PMC4240471; Results and Discussion / Consumption
    of glucose and generation of biomass and ethanol, not the abstract. Introduction,
    relevant Results, Experimental procedures and actual Figures 1-2 were inspected.
    Glucose pulses into initially respiratory cultures produced ethanol in responsive
    yeasts while dissolved oxygen was controlled above 30% air saturation. The authors
    report no first-hour repression of respiration; Figure 2 does not establish monotonic
    or unchanged oxygen-consumption rates. Replication excludes V. polyspora; E. coryli
    received supplementation. This short-term Crabtree assay is not an exact synonym
    for the entire microbial phenotype. Supplemental time series and strain origins
    were not fully reviewed.
discussions:
- discussion_id: aerobic-overflow-scope-and-parent
  prompt: Retain oxygen-sufficient overflow as a conditional phenotype with an explicit
    hierarchy boundary.
  kind: CURATION_TODO
  status: OPEN
  rationale: 'The qualifier aerobic is deliberate. Unqualified overflow, Crabtree
    effect, respiro-fermentation and industrial aerobic fermentation are not asserted
    as exact synonyms. The local METPO:1002005 fermentation record is donor/acceptor-defined
    and excludes external electron acceptors; Basan''s oxidative branch uses different
    accounting. https://github.com/berkeleybop/metpo/issues/468 discusses fermentation
    hierarchy, and the pinned ontology already differs from the retained local parent/definition.
    Neither that process nor METPO:1000060 metabolism is adopted as an is-a parent
    of this organismal phenotype. METPO:1000059 phenotype is used pending upstream
    hierarchy review. Product-specific ethanol/butanediol fermentation, aerotolerance,
    facultative anaerobiosis, copiotrophy and diauxic growth are not equivalent. Product
    detection or oxygen presence alone is insufficient: oxygen limitation must be
    excluded. No universal substrate, product, concentration, growth-rate threshold,
    complete respiratory shutdown or fixed molecular mechanism is required.'
  posed_by: codex
  posed_date: '2026-10-12'
- discussion_id: aerobic-overflow-examples-and-mechanism
  prompt: Resolve natural strain provenance and taxon-specific mechanisms before adding
    canonical examples or a graph.
  kind: KNOWLEDGE_GAP
  status: OPEN
  rationale: Laboratory reference strains and engineered perturbations are qualified
    evidence, not proof that every member of a species has this phenotype under all
    conditions. Canonical taxa require primary strain provenance and authority-resolved
    identities. No common protein-resolved causal graph is established here; bacterial
    and yeast mechanisms must retain their experimental scope. Gene presence and predicted
    flux alone do not demonstrate overflow. Canonical examples, causal graphs and
    external xrefs are therefore unasserted. Qualified MED and Crossref records for
    all three citations exposed no linked correction or retraction on 2026-10-12;
    this bounded check is not a guarantee that no notice exists. Basan's publisher
    access remains unavailable.
  posed_by: codex
  posed_date: '2026-10-12'
curation_history:
- timestamp: '2026-10-12T01:03:22Z'
  curator: codex
  action: MINTED_TRAITMECH_ID
  changes: Added aerobic overflow metabolism with three DOI-backed sources and directly
    checked snippets. Reserved 000705, v581 and 1065800-1065899 after ignored/hidden
    worktree and pending-PR checks. Oxygen-sufficient scope, hierarchy and inference
    limits are explicit. Existing traits unchanged; timestamp is the observed UTC
    curation decision.
  llm_assisted: true
- timestamp: '2026-10-12T01:08:15Z'
  curator: codex
  action: CLARIFIED_EVIDENCE_SCOPE
  changes: 'Address #1881: distinguish the authors'' reported lack of early respiratory
    repression from a claim that individual oxygen-consumption rates never decrease.
    Retain the original curation event unchanged.'
  llm_assisted: true
- timestamp: '2026-10-12T01:53:37Z'
  curator: codex
  action: REPLACED_UNSUPPORTIVE_SNIPPET
  changes: 'Address #1883: replace the yeast data-collection quotation with an 18-word
    Results span that reports significant ethanol formation after a glucose pulse.
    Retain oxygen-controlled assay context, the 25-word bound and both earlier curation
    events unchanged.'
  llm_assisted: true