chemotrophic

METPO:1000641 · CLASS · REVIEWED

A trophic type in which an organism obtains energy from chemical oxidation of either inorganic or organic compounds.

Trait evidence (2)

DOI:10.1016/B978-012373944-5.00083-3
chemical energy

Encyclopedia chapter classifies chemotrophy by chemical energy sources.
DOI:10.1016/j.bbabio.2008.09.008
free energy of a redox reaction

Review supports chemical redox reactions as energy sources for respiratory energy conservation.

Chemotrophic chemical redox energy conservation

DOI-backed graph linking reduced chemical substrates, inorganic and organic donor examples, redox reactions, respiratory electron transfer, proton motive force, and ATP.

MECHANISTIC · This graph represents respiratory chemotrophic energy conservation, not every chemotrophic route; fermentation and substrate-level phosphorylation are outside its scope. The E. coli K-12 AtpD example supports the shared F-type ATP-synthase module and is one beta subunit, not the complete rotary complex.

Edge evidence

chemotrophic has energy source reduced chemical substrate METPO:2007807
Chemotrophy uses chemical substrates as energy sources.
- DOI:10.1016/B978-012373944-5.00083-3 chemical energy Supports chemical energy as the defining chemotrophic energy source.
inorganic compound example of reduced chemical substrate rdfs:subClassOf
Inorganic substrates are chemical energy sources in lithotrophy.
- DOI:10.1016/B978-0-12-378630-2.00219-X oxidize inorganic atoms or molecules Supports inorganic chemical substrates in chemolithotrophic metabolism.
organic compound example of reduced chemical substrate rdfs:subClassOf
Organic substrates are chemical energy sources in organotrophy.
- DOI:10.1016/B978-012373944-5.00083-3 reduced organic compound Supports reduced organic compounds as chemical energy substrates.
reduced chemical substrate oxidized by redox reaction
Chemical energy is released through oxidation-reduction chemistry.
- DOI:10.1016/j.bbabio.2008.09.008 free energy of a redox reaction Supports redox reactions as the energy source for chemiosmotic conservation.
redox reaction feeds electrons into respiratory chain METPO:2007402
Redox reactions can feed electrons into membrane respiratory chains.
- DOI:10.1016/j.bbabio.2008.09.008 membrane-bound electron transport chain Supports membrane electron transport in respiratory energy conservation.
respiratory chain transfers electrons to terminal electron acceptor METPO:2007403
Respiratory chains transfer electrons to terminal acceptors.
- DOI:10.1128/mmbr.61.4.533-616.1997 terminal electron acceptor Supports terminal electron acceptors in respiratory metabolism.
respiratory chain generates proton motive force biolink:produces
Respiratory electron transfer generates an ion gradient.
- DOI:10.1016/j.bbabio.2008.09.008 generation of an electrochemical ion gradient Supports ion-gradient formation by electron transport.
proton motive force drives production of ATP biolink:produces
Proton motive force drives ATP synthesis.
- DOI:10.1016/j.bbabio.2008.09.008 drives ATP synthesis Supports ATP synthesis from chemotrophic respiratory energy conservation.
proton motive force used by ATP synthase
F-type ATP synthase converts proton-motive-force energy into rotary catalysis.
- DOI:10.7554/eLife.21598 the potential energy of the proton motive force into rotation of the central stalk The E. coli F1Fo structural study directly supports proton-motive-force-driven rotation of the ATP synthase represented by this node.
ATP synthase produces ATP biolink:produces
ATP synthase couples ion flow to phosphorylation of ADP.
- DOI:10.7554/eLife.21598 couples ion flow across membranes with the addition of inorganic phosphate to ADP thereby generating ATP The E. coli F1Fo study supports ATP as the catalytic product of the multisubunit ATP synthase; P0ABB4 represents only its beta component.
proton motive force can be built by quinone/quinol cycling
Proton motive force can be generated by quinone/quinol cycling.
- DOI:10.1016/j.bbabio.2008.09.008 The proton motive force (pmf) can be built up by different mechanisms like proton pumping, quinone/quinol cycling or by a redox loop.
proton pumping contributes to generation of proton motive force
Active proton pumping contributes to building the proton motive force.
- DOI:10.1016/j.bbabio.2008.09.008 The proton motive force (pmf) can be built up by different mechanisms like proton pumping, quinone/quinol cycling or by a redox loop.
redox loop contributes to generation of proton motive force
A redox loop contributes to building the proton motive force.
- DOI:10.1016/j.bbabio.2008.09.008 The proton motive force (pmf) can be built up by different mechanisms like proton pumping, quinone/quinol cycling or by a redox loop.
redox loop couples electron transport to net proton transfer across membrane
A redox loop couples electron transport to net proton transfer across the membrane without proton pumping.
- DOI:10.1016/j.bbabio.2008.09.008 The latter couples electron transport to a net proton transfer across the membrane without proton pumping.

Protein and taxon examples

Graph node Protein Taxon UniProt status Role and evidence

ATP synthase

Graph node	Protein	Taxon	UniProt status	Role and evidence
ATP synthase	`UniProtKB:P0ABB4` ATP synthase subunit beta (atpD)	Escherichia coli K-12 `NCBITaxon:83333`	`REVIEWED` retrieved 2026-08-24 · entry v155 · sequence v2	Beta component of the F1 catalytic head of the E. coli F1Fo ATP synthase; this accession is not presented as the complete rotary complex. `DOI:10.7554/eLife.21598` the potential energy of the proton motive force into rotation of the central stalk that drives conformational changes in the F1 catalytic sites The primary cryo-EM study resolves the E. coli F1Fo complex and its beta-containing catalytic head; UniProtKB P0ABB4 verifies the reviewed AtpD component and K-12 taxon.

UniProtKB:P0ABB4
ATP synthase subunit beta (atpD)

Escherichia coli K-12
NCBITaxon:83333

REVIEWED
retrieved 2026-08-24 · entry v155 · sequence v2

Beta component of the F1 catalytic head of the E. coli F1Fo ATP synthase; this accession is not presented as the complete rotary complex.

DOI:10.7554/eLife.21598 the potential energy of the proton motive force into rotation of the central stalk that drives conformational changes in the F1 catalytic sites The primary cryo-EM study resolves the E. coli F1Fo complex and its beta-containing catalytic head; UniProtKB P0ABB4 verifies the reviewed AtpD component and K-12 taxon.

Provenance

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

Parent traits (1)

trophic type METPO:1000631

Synonyms (2)

TT_chemotroph RELATED_SYNONYM · metpo.owl
chemotroph RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

METPO:1000641 [-1.746, -0.197, -4.063, +1.592, …]

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).

physiology organotrophic 0.838
physiology lithotrophic 0.527
physiology chemoorganotrophic 0.506
environment NaCl delta low 0.426
physiology trophic type 0.415
morphology orange pigmented 0.410
environment pH range mid2 0.408
environment temperature delta mid2 0.407

Deep research

Generated by just research-trait; source: research/traits/physiology/chemotrophic-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: microbial chemotrophic trait

## 1. Scope summary

**Target:** `METPO:1000641` — **chemotrophic**; category **PHYSIOLOGY**; term kind **CLASS**; mapping **REVIEWED**; parent `METPO:1000631`.

**Operational definition.** Chemotrophy is the physiological capacity to obtain usable energy from oxidation–reduction reactions involving chemical compounds. A donor is oxidized, electrons pass to an acceptor, and the released free energy is conserved—commonly through a membrane electron-transfer chain, ion-motive force, and ATP synthesis. This agrees with the supplied definition: “A trophic type in which an organism obtains energy from chemical oxidation of either inorganic or organic compounds.” Modern reviews likewise describe chemotrophs as exploiting environmental electron donors and acceptors and respiratory complexes as generating proton-motive force for ATP synthase. (gupta2020extracellularelectronuptake pages 5-6)

### Important boundaries

1. **Chemotrophy is an energy-source classification, not a carbon-source classification.** Chemotrophs may be autotrophic, using CO₂, or heterotrophic, using organic carbon. Therefore, neither “autotrophic” nor “heterotrophic” should be made equivalent to `METPO:1000641`.
2. **Chemolithotrophy** is the subset using inorganic electron donors such as H₂, Fe(II), reduced sulfur compounds, ammonia, nitrite, or CO. **Chemoorganotrophy** uses organic donors. The parent chemotrophic graph should remain donor-agnostic, with these as branches.
3. **Phototrophy** differs because light is the primary energy input. A facultative organism can express both modes under different conditions, but phototrophic growth alone is not evidence for chemotrophy.
4. **Aerobic versus anaerobic respiration** concerns the terminal acceptor, not whether an organism is chemotrophic. Oxygen, nitrate, sulfate, sulfur species, metals, and other compounds can serve as acceptors in different taxa. Sulfur oxidizers, for example, couple reduced-sulfur oxidation to oxygen or nitrate reduction. (gupta2020extracellularelectronuptake pages 8-9)
5. **Fermentation is a boundary case.** It is chemical energy metabolism, but it lacks an external terminal electron acceptor and often conserves energy by substrate-level phosphorylation. Curating fermentation under this broad METPO definition may be defensible, but a respiratory-chain mechanism must not be asserted for every fermentative chemotroph.
6. **Electroautotrophy/electrolithotrophy is another boundary case.** Electrode-derived electrons can support metabolism and CO₂ fixation, but an electrode is not conventionally a molecular compound. It should be represented as an assay-specific extension or sibling mode rather than silently generalized to all chemotrophy. (wang2024characterizethegrowth pages 22-23, llorente2024novelelectrochemicalstrategies pages 1-2)
7. **Genes alone do not establish the trait.** Detection of `sox`, hydrogenase, or carbon-fixation genes supports metabolic potential, but physiological evidence requires donor-dependent growth, substrate turnover, energy conservation, or comparable functional measurements.

## 2. Recommended graph architecture

The existing 13-node/12-edge graph appears appropriately sized for a **minimal core**, but it should separate universal bioenergetics from taxon-specific examples:

**chemical electron donor → donor oxidation/redox reaction → electron transfer → energy-conserving membrane complex → ion-motive force → ATP synthase → ATP → growth/maintenance**

Add conditional branches for:

- terminal electron acceptor reduction;
- reverse electron transport and reducing-equivalent generation;
- carbon fixation only for chemoautotrophs;
- substrate-level phosphorylation for fermentative chemoorganotrophs;
- donor-specific modules such as Fe(II)/Cyc2/Rus or thiosulfate/Sox.

The literature supports outer-membrane cytochromes, periplasmic carriers, and inner-membrane respiratory complexes as an electron-transfer route that generates proton-motive force, which ATP synthase uses to make ATP. Reverse electron flow can generate NADH for CO₂ fixation. (gupta2020extracellularelectronuptake pages 5-6)

## 3. Candidate nodes grouped by type

Ontology identifiers below are limited to high-confidence mappings. Labels without CURIEs should undergo ontology lookup before YAML insertion.

### Trait and taxon/context nodes

- chemotrophic — `METPO:1000641`
- chemolithotrophy — label-only pending METPO verification
- chemoorganotrophy — label-only pending METPO verification
- chemoautotrophy — label-only pending METPO verification
- *Acidithiobacillus ferrooxidans* — NCBITaxon identifier should be verified at curation time
- *Hydrogenovibrio* strain 104 / hydrothermal-vent *Hydrogenovibrio* isolates — strain-specific label
- sulfate-reducing bacteria — taxonomic/functional group; not one NCBITaxon node
- autotrophic electroactive microbial enrichment — assay-community node

### Chemicals and environmental substrates

- chemical electron donor — role node; label-only
- chemical electron acceptor — role node; label-only
- dioxygen — `CHEBI:15379`
- carbon dioxide — `CHEBI:16526`
- proton — `CHEBI:15378`
- ATP — `CHEBI:30616`
- Fe(II), Fe(III), molecular hydrogen, sulfide, elemental sulfur, thiosulfate, nitrate, sulfate, water, NADH, acetate, formate, propionate — use ChEBI after identifier validation
- reduced inorganic sulfur compounds — collection/class node rather than a single molecule
- polarized carbon electrode — experimental-factor/material node

Showing the first 60 of 253 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.

Escherichia coli K-12 NCBITaxon:83333 DOI:10.7554/eLife.21598 Strain-level chemoorganotrophic respiratory model paired to the reviewed AtpD beta component of its F-type ATP synthase.

Curation history

2026-05-05T01:35:46.872607+00:00 · SEEDED_FROM_METPO · seed_from_metpo
imported from data/raw/metpo.owl (CLASS)
2026-05-09T00:00:00-07:00 · ADDED_CAUSAL_GRAPH · codex
Added DOI-backed causal graph for chemical substrate oxidation, respiratory electron transfer, proton motive force, and ATP synthesis.
2026-05-20T03:35:31Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000010×1).
2026-05-23T08:21:50Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (rdfs:subClassOf×2, biolink:produces×1).
2026-05-23T21:30:07Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007402×1, METPO:2007403×1).
2026-05-24T04:38:01Z · GROUND_CAUSAL_NODES · claude
Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0016491×1, GO:0022904×1).
2026-05-24T04:41:04Z · GROUND_CAUSAL_NODES · claude
Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (METPO:1007504×1, METPO:1007500×1).
2026-05-24T08:14:33Z · GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:50860×1).
2026-05-26T02:30:13Z · 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.
2026-06-13T21:03:27Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:produces×1).
2026-06-23T00:00:00Z · ENRICH_CAUSAL_GRAPH · claude
Added 4 evidence-backed generic edges (4 new nodes) from the deep-research report.
2026-08-06T01:00:00Z · MIGRATE_MICROBE_DOMAIN_EDGES · claude
Re-grounded 1 causal edge(s) off microbe-domain METPO predicates (1 to has energy 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.
2026-08-24T12:30:00-07:00 · REVIEWED_CAUSAL_GRAPH_PROTEIN_TAXON · codex
Marked the respiratory chemotrophy graph mechanistic, documented its scope, added DOI-cited E. coli K-12 as the canonical strain, and paired the generic ATP synthase complex with reviewed AtpD component P0ABB4 without treating one subunit as the whole complex.