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chemoheterotrophic

METPO:1000636 · CLASS · REVIEWED

A trophic type in which an organism obtains both energy and carbon from organic compounds.

Trait evidence (2)

Chemoheterotrophic organic energy and carbon metabolism

DOI-backed graph linking organic molecules as chemical energy and carbon sources to catabolism, respiration or fermentation, ATP, and biomass.

MECHANISTIC · This broad graph combines respiratory, fermentative, glycolytic, and mannitol-utilization branches rather than asserting one universal route. The E. coli K-12 MtlD example anchors only mannitol-1-phosphate conversion and does not represent the multicomponent PTS or all chemoheterotrophic catabolism.

Chemoheterotrophic organic energy and carbon metabolism Interactive directed graph showing evidence-backed causal relationships for chemoheterotrophic.

Edge evidence

  • chemoheterotrophic has energy source organic molecule METPO:2007807

    Chemoheterotrophs derive chemical energy from organic compounds.

    • DOI:10.1021/acsomega.3c02205 organic molecules ... energy source Supports organic molecules as energy sources in chemoheterotrophic growth.
  • chemoheterotrophic has carbon source organic molecule METPO:2007806

    Chemoheterotrophs use organic compounds as carbon sources.

  • organic molecule broken down by catabolism

    Organic molecules are catabolized to release energy and precursors.

  • catabolism can proceed through respiration

    Organic catabolism can conserve energy through respiration.

  • catabolism can proceed through fermentation

    Organic catabolism can conserve energy through fermentation.

    • DOI:10.3389/fmicb.2021.703525 substrate ... electron donor as well as acceptor Supports fermentation of organic substrates without external electron acceptors.
  • respiration has output ATP RO:0002234

    Respiration supports ATP synthesis.

  • fermentation has output ATP RO:0002234

    Fermentation can produce ATP by substrate-level phosphorylation.

  • catabolism has output precursor metabolites RO:0002234

    Catabolism supplies precursors for biosynthesis.

  • precursor metabolites incorporated into biomass biolink:part_of

    Organic-carbon precursors are incorporated into biomass.

  • Embden-Meyerhof glycolysis pathway contributes to catabolism RO:0002326

    Embden-Meyerhof glycolysis is a core route of organic-substrate catabolism in chemoheterotrophs.

    • DOI:10.1128/mbio.00992-24 harbor the Embden-Meyerhof-Parnas glycolysis pathway; broad mechanistic core of chemoheterotrophic catabolism.
  • fermentation generates short-chain fatty acids biolink:produces

    Fermentation of organic substrates yields short-chain fatty acids such as acetate, succinate, and propionate.

    • DOI:10.1016/j.chom.2024.05.011 subsequent fermentation to short-chain fatty acids (acetate, succinate, propionate); broadly useful fermentation output edge.
  • PEP-dependent phosphotransferase system (mannitol PTS) imports and phosphorylates mannitol

    A PEP-dependent phosphotransferase system imports and phosphorylates mannitol as an organic substrate.

  • mtlD mannitol-1-phosphate dehydrogenase converts fructose-6-phosphate

    mtlD converts mannitol-1-phosphate to fructose-6-phosphate, feeding catabolism into glycolysis.

  • fructose-6-phosphate broken down by Embden-Meyerhof glycolysis pathway

    Fructose-6-phosphate is metabolized through the Embden-Meyerhof glycolysis pathway.

  • mannitol participates in catabolism biolink:participates_in

    Imported mannitol is converted through mannitol-1-phosphate and fructose-6-phosphate before entering glycolytic catabolism.

    • DOI:10.1371/journal.pbio.3002198 mannitol 1P (toxic when accumulating) is oxidized by MtlD to fructose 6P, where it enters glycolysis Verified against the open PLOS Biology primary article.

Protein and taxon examples

Graph nodeProteinTaxonUniProt statusRole and evidence
mtlD mannitol-1-phosphate dehydrogenase UniProtKB:P09424
Mannitol-1-phosphate 5-dehydrogenase (mtlD) 		Escherichia coli K-12
NCBITaxon:83333 		REVIEWED
retrieved 2026-08-24 · entry v187 · sequence v3

E. coli MtlD enzyme catalyzing the mannitol-1-phosphate dehydrogenase step that connects PTS uptake to fructose-6-phosphate and glycolysis.

  • DOI:10.1128/jb.159.3.986-990.1984 Purification and properties of D-mannitol-1-phosphate dehydrogenase from Escherichia coli The primary purification study establishes the E. coli enzyme and catalytic activity; UniProtKB P09424 is the reviewed K-12 MtlD entry.

Provenance

Identifier source
METPO (2026-06-12)
Definition source
DOI:10.1016/B978-012373944-5.00083-3

Parent traits (1)

Synonyms (2)

  • aerobic_chemo_heterotrophy RELATED_SYNONYM · metpo.owl
  • chemoheterotroph RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000636 [-2.849, -3.249, -2.560, +0.024, …]

512-dim DeepWalkSkipGramEnsmallen embedding from kg-microbe (2026-04-25).

Nearest neighbors in embedding space

Top-8 cosine-similar METPO traits from the 2026-04-25 deepwalk (512-D).

Deep research

Generated by just research-trait; source: research/traits/physiology/chemoheterotrophic-deep-research-falcon.md

Unreviewed literature output — not curated TraitMech content Ontology identifiers suggested below have not been resolved against their ontologies, and some are known to be wrong. Check any CURIE against the source before using it. 
# Curation report: chemoheterotrophic (`METPO:1000636`)

## Executive scope summary

`METPO:1000636` denotes a **trophic capacity in which organic compounds provide both carbon and chemical energy**. It is broader than *aerobic chemoheterotrophy*: oxygen-dependent respiration is one possible implementation, while anaerobic respiration and fermentation are also compatible branches. It is not synonymous with degradation of every organic substrate, obligate heterotrophy, growth in darkness, or a particular respiratory pathway.

The most defensible TraitMech graph is therefore a compact, substrate-to-growth core:

**extracellular organic compound → uptake/depolymerization → central carbon metabolism → (i) carbon skeletons and (ii) reducing equivalents/ATP → biomass formation**, with separate optional branches for aerobic respiration, anaerobic respiration, and fermentation.

The 2023 cyanobacterial review is especially useful for scope: chemoorganoheterotrophic growth uses organic molecules as carbon and energy sources, but substrate range varies by strain. It also shows why darkness should be an assay condition rather than part of the universal definition: dark growth is particularly diagnostic in phototrophic cyanobacteria, whereas many non-phototrophic chemoheterotrophs do not require darkness. (stebegg2023heterotrophyamongcyanobacteria pages 2-2, stebegg2023heterotrophyamongcyanobacteria pages 1-2)

## 1. Trait boundaries and nearby concepts

- **Chemoheterotrophy versus photoheterotrophy:** both use organic carbon, but photoheterotrophs derive energy primarily from light. A cyanobacterium may switch among modes according to environmental conditions, so trophic annotations can be conditional rather than organism-wide absolutes. (stebegg2023heterotrophyamongcyanobacteria pages 2-2, stebegg2023heterotrophyamongcyanobacteria pages 14-15)
- **Chemoheterotrophy versus autotrophy:** autotrophs obtain biomass carbon primarily through inorganic-carbon fixation. Absence of a carbon-fixation pathway can support heterotrophy, but genome content alone does not demonstrate growth on organic compounds. SAR86, for example, lacks autotrophic fixation pathways and contains pathways for organic-carbon use, supporting—but still genomically inferring—an obligately heterotrophic lifestyle. (dupont2012genomicinsightsto pages 8-9)
- **Chemoheterotrophy versus mixotrophy:** mixotrophs can combine or switch between organic-carbon use and autotrophic carbon fixation. A condition-specific chemoheterotrophic growth result should not automatically classify the organism as an obligate chemoheterotroph. The 2023 review calls cyanobacteria “multitrophs” that adopt different modes under different conditions. (stebegg2023heterotrophyamongcyanobacteria pages 14-15)
- **Aerobic chemoheterotrophy:** a child or compositional phenotype requiring oxygen-linked respiration. Oxygen must not be placed in the universal parent graph.
- **Anaerobic respiratory chemoheterotrophy:** organic substrate supplies carbon and normally reducing power, while nitrate, sulfate, Fe(III), or another external acceptor supports respiration. Buckel explicitly distinguishes such acceptor-dependent metabolism from fermentation. (buckel2021energyconservationin pages 1-2)
- **Fermentative chemoheterotrophy:** the organic substrate functions as both electron donor and acceptor; energy may be conserved through substrate-level phosphorylation and, in some anaerobes, ion-gradient mechanisms. Fermentation has much lower thermodynamic yield than complete aerobic glucose oxidation: the reviewed comparison reports fermentation-scale values below about −20 kJ mol⁻¹ versus −2,872 kJ mol⁻¹ for aerobic glucose oxidation. (buckel2021energyconservationin pages 1-2)
- **Assay phenotype:** suitable evidence includes reproducible growth or biomass increase in a defined medium where an organic compound supplies carbon and energy, preferably with no alternative energy source. Substrate disappearance, respiration, fermentation products, ATP production, or isotope incorporation can strengthen the conclusion.

## 2. Candidate graph nodes

### Trait and phenotype nodes

- `chemoheterotrophic` — **`METPO:1000636`**
- chemoheterotrophic growth
- aerobic chemoheterotrophy
- anaerobic respiratory chemoheterotrophy
- fermentative chemoheterotrophy
- mixotrophic growth — label-only pending ontology review
- biomass formation / cellular growth — GO grounding should be verified during curation

### Environmental and experimental nodes

- organic-carbon availability; dissolved organic carbon
- organic compound as sole carbon and energy source
- light/dark condition — diagnostic mainly for phototrophic taxa
- oxic, microoxic, and anoxic conditions
- oxygen availability
- alternative terminal-electron-acceptor availability
- temperature, salinity, pH, and hydrostatic pressure as taxon-specific modifiers
- defined-medium growth assay; substrate-utilization assay
- respirometry; fermentation-product measurement
- stable-isotope tracing, especially `13C` incorporation or `13CO2` production

### Chemicals and nutrients

Recommended high-confidence chemical candidates, with identifiers to validate against the current ChEBI release before committing:

- organic compound / organic carbon source — generic label may be preferable
- glucose — `CHEBI:17234`
- fructose — `CHEBI:15824`
- sucrose — `CHEBI:17992`
- glycerol — `CHEBI:17754`
- pyruvate — protonation-state-specific ChEBI term must be selected deliberately
- acetyl-CoA — `CHEBI:15351`
- oxygen — `CHEBI:15379`
- nitrate — `CHEBI:17632`

Showing the first 60 of 241 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.

Canonical examples (3)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

Curation history

  1. · SEEDED_FROM_METPO · seed_from_metpo

    imported from data/raw/metpo.owl (CLASS)

  2. · ADDED_CAUSAL_GRAPH · codex

    Added DOI-backed causal graph for organic molecules as energy and carbon sources feeding catabolism, respiration or fermentation, ATP, and biomass.

  3. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 5 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×3, METPO:2000010×1, METPO:2000006×1).

  4. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (METPO:1007501×1).

  5. · RETYPE_CAUSAL_NODES · claude

    Re-typed 1 causal-node node_type field(s) to align with CausalNodeTypeEnum semantics: biomass: BIOLOGICAL_PROCESS → CHEMICAL ×1.

  6. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:part_of×1).

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:72695×1).

  8. · ENRICH_CAUSAL_GRAPH · claude

    Added 5 evidence-backed generic edges (6 new nodes) from the deep-research report.

  9. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002326×1, biolink:produces×1).

  10. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:26666×1).

  11. · MIGRATE_MICROBE_DOMAIN_EDGES · claude

    Re-grounded 5 causal edge(s) off microbe-domain METPO predicates (1 to has energy source, 1 to has carbon source, 3 to has output), issue 301. The previous predicates are transitively rdfs:subPropertyOf METPO:2000001, whose rdfs:domain is METPO:1000525 (microbe), so a causal-graph subject entailed that the subject IS a microbe; CausalNodeTypeEnum has no organism member, so no such edge could ever satisfy the domain. Edge directions are unchanged - this pass only relabels and re-grounds. RO:0002234 (has output) is used where the subject is an activity, since biolink gives it the domain 'biological process or activity'; the METPO replacements are proposed in proposals/metpo_traitmech_v8 and v9 and are placeholder ids until METPO mints them.

  12. · NORMALISE_NODE_TYPE · claude

    Under the PATHWAY-vs-BIOLOGICAL_PROCESS rule, one node_id means one thing corpus-wide (issue 356): fermentation is typed BIOLOGICAL_PROCESS. PATHWAY is a named, conventionally enumerable multi-step route; BIOLOGICAL_PROCESS is everything else. A CLASS of routes rather than one route -- fermentation names a mode of energy conservation with many distinct implementations, so its steps cannot be enumerated without picking one. Was 3 BIOLOGICAL_PROCESS to 2 before this tranche. NOTE its groundings disagree with each other (GO:0006113 x3, METPO:1002005, and METPO:1000845 which is ACETOGENESIS, a different concept) -- filed as #391 and deliberately NOT touched here, because retyping a node while carrying a wrong CURIE along unchanged would make it look reviewed.

  13. · REVIEWED_CAUSAL_GRAPH_PROTEIN_TAXON · codex

    Marked the graph mechanistic, scoped its alternative catabolic branches, reviewed the multicomponent mannitol PTS as label-only, and added DOI-cited E. coli K-12 MtlD P09424 with an exact InterPro family grounding.

  14. · CONNECT_CAUSAL_GRAPH_COMPONENTS · codex

    Resolved issue #183 graph fragmentation (2 components to 1) with 1 public-source, verbatim-snippet-backed connector(s). No paid research service was called.