TraitMech

TraitMech › PHYSIOLOGY

chemolithoheterotrophic

METPO:1000638 · CLASS · REVIEWED

A trophic type characterized by the use of inorganic chemical compounds as electron donors for energy generation while utilizing organic compounds as the primary carbon source.

Trait evidence (2)

  • DOI:10.1038/s41598-021-81412-3
    chemolithoheterotrophy

    Experimental study supports chemolithoheterotrophy as Fe(II) oxidation for energy with glucose as carbon source.

  • DOI:10.1128/mBio.01112-19
    oxidize sulfur to fuel the uptake of organic compounds

    Study supports sulfur oxidation coupled to organic compound uptake in a chemolithoheterotrophic symbiont context.

Chemolithoheterotrophic inorganic chemical energy and organic carbon use

DOI-backed graph linking inorganic chemical electron donors, Fe(II) and reduced sulfur examples, respiratory energy conservation, organic carbon uptake, and biomass.

MECHANISTIC · This modular graph covers Fe(II), reduced-sulfur, and H2 donor branches coupled to organic-carbon assimilation. The S. alaskensis example anchors only the H2 branch; Q1J422 is the catalytic large-subunit component of its group 2a hydrogenase, not the complete multisubunit enzyme or the sulfur/iron branches.

Chemolithoheterotrophic inorganic chemical energy and organic carbon use Interactive directed graph showing evidence-backed causal relationships for chemolithoheterotrophic.

Edge evidence

  • chemolithoheterotrophic has electron donor inorganic chemical donor METPO:2007701

    Inorganic chemical compounds serve as the electron donors for chemolithoheterotrophy.

  • ferrous iron example of inorganic chemical donor rdfs:subClassOf

    Fe(II) is an experimentally supported inorganic donor for chemolithoheterotrophy.

  • reduced sulfur compound example of inorganic chemical donor rdfs:subClassOf

    Reduced sulfur compounds can fuel chemolithoheterotrophic metabolism.

    • DOI:10.1128/mBio.01112-19 oxidize sulfur to fuel Supports sulfur oxidation as an energy source coupled to organic compound uptake.
  • molecular hydrogen example of inorganic chemical donor rdfs:subClassOf

    H2 is a reduced inorganic donor that can supplement energy during organic-carbon-supported growth.

    • DOI:10.1038/s41564-023-01322-0 uses an abundant reduced gas as an energy source The culture study shows that S. alaskensis consumes H2 while growing on organic carbon, supporting H2 as the inorganic energy donor in this branch.
  • molecular hydrogen oxidized by group 2a [NiFe]-hydrogenase

    The group 2a uptake hydrogenase mediates aerobic H2 oxidation in S. alaskensis.

    • DOI:10.1038/s41564-023-01322-0 encodes a plasmid-borne group 2a [NiFe]-hydrogenase, aerobically consumed H2 The primary growth, gas-consumption, and hucL-expression experiments pair the enzyme class with H2 oxidation in strain RB2256; Q1J422 is only its large-subunit component.
  • inorganic chemical donor feeds electrons into respiratory chain METPO:2007402

    Oxidized inorganic donors feed electrons into respiratory energy conservation.

  • respiratory chain generates proton motive force biolink:produces

    Respiratory electron transfer generates an ion gradient.

  • proton motive force drives production of ATP biolink:produces

    Proton motive force powers ATP synthesis.

  • chemolithoheterotrophic has carbon source organic compound METPO:2007806

    Organic compounds provide carbon for chemolithoheterotrophic growth.

  • organic compound imported by organic nutrient uptake

    Organic compounds are taken up for heterotrophic carbon assimilation.

  • organic nutrient uptake supports formation of biomass

    Uptaken organic carbon supports cell-material production.

  • Sox sulfur-oxidation pathway has output sulfate RO:0002234

    The conserved soxCDYZAXB gene cluster enables complete oxidation of thiosulfate to sulfate without free intermediates.

    • DOI:10.1038/s41396-021-01163-x Gene clusters of the conserved soxCDYZAXB gene order facilitate the complete oxidation of thiosulfate to sulfate, without free intermediates.
  • thiosulfate oxidized by Sox sulfur-oxidation pathway

    Thiosulfate, a reduced inorganic sulfur donor, is oxidized by the Sox pathway.

  • branched thiosulfate oxidation pathway produces intermediate elemental sulfur

    Truncated soxXYZAB with reverse Dsr/Apr/Sat oxidizes thiosulfate via an elemental sulfur intermediate.

    • DOI:10.1038/s41396-021-01163-x Branched thiosulfate oxidation pathway in which Dsr operating in reverse oxidizes sulfane-derived sulfur to sulfite, with elemental sulfur as intermediate.
  • organic carbon import system supports organic nutrient uptake

    Amino acid and carboxylic acid import systems support organic carbon uptake in heterotrophs and mixotrophs.

    • DOI:10.1038/s41396-021-01163-x Import systems for amino acids and carboxylic acids were overly abundant in mixotrophs and heterotrophs, supporting the organic-carbon dependency of the trait.
  • thiosulfate example of reduced sulfur compound rdfs:subClassOf

    Thiosulfate is a reduced sulfur electron donor oxidized during chemolithomixotrophic growth.

    • DOI:10.1111/1462-2920.13232 obligate aerobic chemolithomixotroph that can oxidize sulfide, thiosulfate and elemental sulfur Verified against the open primary article.
  • branched thiosulfate oxidation pathway contributes to respiratory chain RO:0002326

    Branched thiosulfate oxidation transfers substrate electrons into respiratory cytochromes.

    • DOI:10.1128/AEM.00956-13 oxidizes sulfone, as well as sulfane, sulfur atoms to sulfate by transferring electrons to c-type cytochromes Verified against the open primary article.

Protein and taxon examples

Graph nodeProteinTaxonUniProt statusRole and evidence
group 2a [NiFe]-hydrogenase UniProtKB:Q1J422
Group 2a [NiFe]-hydrogenase large subunit HucL (Sala_3198) 		Sphingopyxis alaskensis RB2256
NCBITaxon:317655 		UNREVIEWED
retrieved 2026-08-24 · entry v98 · sequence v1

Catalytic large-subunit component of the plasmid-borne group 2a [NiFe]-hydrogenase; this accession is not presented as the complete hydrogenase complex.

  • DOI:10.1038/s41564-023-01322-0 group 2a [NiFe]-hydrogenase large subunit gene (hucL; locus Sala_3198) The primary study measured Sala_3198 expression during aerobic growth and H2 oxidation. UniProtKB Q1J422 maps that exact locus to the S. alaskensis RB2256 reference proteome.

Provenance

Identifier source
METPO (2026-06-12)
Author
Anthea Guo
Definition source
DOI:10.1038/s41598-021-81412-3

Parent traits (1)

Synonyms (1)

  • chemolithoheterotroph RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000638 [-3.114, -0.723, -4.275, +1.898, …]

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/chemolithoheterotrophic-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-focused research report: chemolithoheterotrophic

## 1. Trait record and scope

- **Trait label:** chemolithoheterotrophic
- **Trait identifier:** **METPO:1000638**
- **Category / kind / status:** PHYSIOLOGY / CLASS / REVIEWED
- **Parent:** METPO:1000631
- **Synonym:** chemolithoheterotroph

### Operational definition

The trait describes a trophic strategy in which a microorganism obtains respiratory energy/electrons from oxidation of an **inorganic chemical donor**, while **organic compounds provide the primary assimilated carbon for biomass**. The strongest operational test therefore combines:

1. oxidation of an inorganic donor;
2. respiration or another demonstrated energy-conserving process;
3. uptake and assimilation of labeled organic carbon; and
4. absent or quantitatively negligible autotrophic CO2 assimilation.

*Arcobacter peruensis* provides a particularly strong assay-level example: it oxidized sulfide, completely reduced nitrate to N2, assimilated acetate, and showed negligible bicarbonate assimilation. Its genome also lacked canonical autotrophic CO2-fixation machinery (callbeck2019arcobacterperuensissp. pages 1-2, callbeck2019arcobacterperuensissp. pages 7-9, callbeck2019arcobacterperuensissp. pages 5-7).

### Boundaries with adjacent traits

| Nearby trait | Energy/electron source | Primary biomass carbon | Curation distinction |
|---|---|---|---|
| **Chemolithoheterotrophy** | Inorganic donor | Organic carbon | Target trait; require evidence that inorganic oxidation benefits energy metabolism and organics supply biomass carbon. |
| **Chemolithoautotrophy** | Inorganic donor | CO2/HCO3− | Exclude when canonical carbon fixation and substantial inorganic-carbon assimilation sustain biomass. |
| **Chemoorganoheterotrophy** | Organic donor | Organic carbon | Exclude if sulfur or Fe transformations are detoxification/incidental and do not contribute energy. |
| **Mixotrophy** | Often both inorganic and organic donors | Both inorganic and organic carbon | Do not automatically merge with this trait. A facultative organism can express chemolithoheterotrophy under one condition and mixotrophy under another. |
| **Lithoheterotrophic genomic potential** | Predicted inorganic oxidation | Predicted organic uptake | Treat as uncertain unless physiology, isotope incorporation, or condition-specific expression links both modules. |

The Kentron symbionts illustrate a genome-supported boundary: they possess sulfur-based energy metabolism but lack RuBisCO and key enzymes of the canonical autotrophic pathways. Their assignment is compelling but remains less direct than pure-culture isotope physiology because organic-carbon use was reconstructed from multi-omics rather than demonstrated in an isolated growth experiment (seah2019sulfuroxidizingsymbiontswithout pages 2-4).

## 2. Current evidence and recent developments

Trait-specific mechanistic evidence remains concentrated in well-resolved 2019 studies rather than in 2023–2024 publications. The recent literature retrieved for 2023–2024 largely concerned sulfur biotechnology, genomes, or autotrophic iron oxidation and did not provide stronger direct chemolithoheterotrophic physiology. Such sources should inform pathway context, not serve as primary evidence for this trait.

A notable post-2024 development is a 2025 *Nature Communications* study of estuarine nitrate-respiring heterotrophs. DNA stable-isotope probing indicated that sulfur oxidation can augment heterotrophic denitrification: sulfide addition increased organic-carbon assimilation by **64.1% in Azoarcus** and **8.0% in Pseudomonas**. The work also reported complete denitrification and reduced N2O release in organic-rich and organic-limited conditions. This broadens chemolithoheterotrophy from exceptional isolates to potentially important estuarine functional guilds, although these effects remain taxon- and incubation-specific (shao2025versatilenitraterespiringheterotrophs pages 1-2).

Groundwater microcosm work similarly suggests that reduced-sulfur oxidation can conserve organic substrates for biosynthesis. Fifteen sulfur-oxidizing MAGs encoded cytochrome-c oxidase and respiratory-chain functions, while twelve encoded nitrate-reduction enzymes. However, that work emphasized mixotrophic communities and did not isolate chemolithoheterotrophic growth in pure culture; those edges should remain provisional (taubert2021bolsteringfitnessvia pages 15-19).

## 3. Candidate causal-graph nodes

Identifiers below are supplied only where confidence is high. Labels are deliberately retained without CURIEs when database-specific verification was unavailable; this avoids inventing identifiers.

### Trait and taxa

- **METPO:1000638** — chemolithoheterotrophic
- *Arcobacter peruensis* PSE-93 / BCCM LMG-31510 — label-only taxon node pending current NCBITaxon verification
- “Candidatus Kentron” — label-only clade node
- *Kentrophoros* host ciliates — label-only taxon node
- sulfur-stimulated groundwater microbial community — community-level node, uncertain
- estuarine nitrate-respiring heterotrophs, including *Azoarcus* and *Pseudomonas* — taxon-specific 2025 extension

### Chemicals and nutrients

- sulfide / hydrogen sulfide — inorganic electron donor
- thiosulfate — inorganic electron donor
- elemental sulfur — inorganic electron donor/intermediate
- nitrate — terminal electron acceptor

Showing the first 60 of 235 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 (1)

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

  • Sphingopyxis alaskensis RB2256 NCBITaxon:317655 DOI:10.1038/s41564-023-01322-0 Strain-level facultative chemolithoheterotrophic example that oxidizes H2 during aerobic growth on organic carbon, paired to its group 2a hydrogenase large subunit.

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 inorganic chemical donors, Fe(II), reduced sulfur, respiratory energy conservation, organic nutrient uptake, and biomass.

  3. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000009×1, METPO:2000006×1).

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (rdfs:subClassOf×2, biolink:produces×1).

  5. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007402×1).

  6. · GROUND_CAUSAL_NODES · claude

    Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:29033×1, GO:0022904×1).

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (METPO:1007500×1, METPO:1007501×1).

  8. · RETYPE_CAUSAL_NODES · claude

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

  9. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:50860×1).

  10. · RETYPE_CAUSAL_NODES · claude

    Re-typed 1 causal-node node_type field(s) to align with CausalNodeTypeEnum semantics: proton motive force: BIOLOGICAL_PROCESS → STATE ×1.

  11. · GROUND_CAUSAL_PREDICATES · claude

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

  12. · ENRICH_CAUSAL_GRAPH · claude

    Added 4 evidence-backed generic edges (6 new nodes) from the deep-research report.

  13. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002327×1).

  14. · GROUND_CAUSAL_NODES · claude

    Grounded 3 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:16094×1, CHEBI:16189×1, CHEBI:26833×1).

  15. · REVERSE_CAUSAL_EDGE_DIRECTION · claude

    Reversed 1 causal edge from <trait> uses electron donor <chemical> to <chemical> enables <trait> (predicate_id METPO:2000009 -> RO:0002327), issue 295. METPO:2000009 is rdfs:subPropertyOf METPO:2000001, whose rdfs:domain is METPO:1000525 (microbe), so the trait-subject form entailed that this TRAIT node is a microbe; CausalNodeTypeEnum has no organism member, so no causal-graph edge can satisfy that domain. Evidence unchanged; only subject/predicate/object/predicate_id and the edge description moved. Note RO:0002327 has range 'biological process or activity', so the new form is not fully range-correct either - tracked in issue 302.

  16. · MIGRATE_ENABLES_TRAIT_EDGES · claude

    Migrated 1 causal edge(s) off enables/RO:0002327 with a TRAIT object (1 to has electron donor), issue 302. RO:0002327 has range 'biological process or activity', which a trait (a disposition) cannot satisfy, so the previous form entailed trait is-a BiologicalProcessOrActivity. The replacements are proposed in proposals/metpo_traitmech_v8 and are placeholder ids until METPO mints them. 1 electron edge(s) were also reversed back to trait -> chemical, restoring the donor/acceptor role that PR 300 collapsed onto enables (issue 303); the organism-subject problem that forced that collapse does not arise here because these predicates take a causal-node domain rather than METPO:2000001's microbe domain (issue 301).

  17. · MIGRATE_MICROBE_DOMAIN_EDGES · claude

    Re-grounded 1 causal edge(s) off microbe-domain METPO predicates (1 to has carbon source), 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.

  18. · REGROUND_CAUSAL_EDGE · claude

    Edge sox_pathway -> sulfate in graph chemolithoheterotrophic_inorganic_energy_organic_carbon: re-grounded it from enables/RO:0002327 to has output/RO:0002234. Issue 334. biolink declares enables range 'biological process or activity', which of CausalNodeTypeEnum only BIOLOGICAL_PROCESS, PATHWAY and MOLECULAR_FUNCTION satisfy, so this edge entailed a false type on its object. The subject IS an activity (PATHWAY), which is the documented dividing line: activity subjects take RO:0002234, whose domain 'biological process or activity' they satisfy, rather than the METPO term minted for the subjects RO cannot cover.

  19. · REVIEWED_CAUSAL_GRAPH_PROTEIN_TAXON · codex

    Marked the graph mechanistic, reviewed the broad importer as label-only, added DOI-cited S. alaskensis RB2256 and its H2 branch, and paired the group 2a hydrogenase node with reference-proteome component Q1J422 without treating one large subunit as the complete complex.

  20. · CONNECT_CAUSAL_GRAPH_COMPONENTS · codex

    Resolved issue #183 graph fragmentation (3 components to 1): added 2 public-source connector(s). No paid research service was called.