autotrophic
METPO:1000632 · CLASS · REVIEWED
A trophic type in which an organism produces organic compounds from inorganic carbon sources (primarily carbon dioxide or bicarbonate) using energy from light (photoautotrophy) or from the oxidation of inorganic compounds (chemoautotrophy).
Autotrophic inorganic carbon fixation
Edge evidence
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autotrophic
has carbon source
carbon dioxide
METPO:2007806Autotrophs use CO2 as an inorganic carbon source.
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DOI:10.1038/nrmicro.2016.130require only CO2 as a carbon source
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bicarbonate
alternative inorganic carbon source for
autotrophic
Bicarbonate is another inorganic carbon species available for autotrophic fixation.
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DOI:10.1128/AEM.02473-10autotrophic carbon dioxide assimilation pathway
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energy and reductant
regulates
CO2-fixation pathway
RO:0002211Autotrophic carbon fixation requires energy and reducing power.
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DOI:10.1038/nrmicro2365energy demand of the autotrophic pathways
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carbon dioxide
fixed by
CO2-fixation pathway
METPO:2007404CO2 is converted into organic carbon by autotrophic fixation pathways.
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DOI:10.1128/AEM.02473-10autotrophic CO2 fixation
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Calvin-Benson cycle
example of
CO2-fixation pathway
rdfs:subClassOfThe Calvin-Benson cycle is a major autotrophic CO2-fixation pathway.
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DOI:10.1128/AEM.02473-10Calvin-Benson reductive pentose phosphate cycle
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RuBisCO
catalyzes
Calvin-Benson cycle
biolink:catalyzesRuBisCO is the key carboxylating enzyme of the Calvin-Benson cycle.
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DOI:10.1128/AEM.02473-10ribulose-1,5-bisphosphate carboxylase
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CO2-fixation pathway
has output
precursor metabolites
RO:0002234Fixed carbon is converted into central biosynthetic precursors.
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DOI:10.1128/AEM.02473-10converted to other central intermediates
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precursor metabolites
incorporated into
biomass
biolink:part_ofFixed-carbon precursors are incorporated into cellular biomass.
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DOI:10.1038/nrmicro.2016.130microbial autotrophic production
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environmental pH
determines speciation of
dissolved inorganic carbon
pH sets the relative abundance of CO2, bicarbonate, and carbonate available for fixation.
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DOI:10.1128/aem.01557-23
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carbon-concentrating mechanism
supplies substrate to
CO2-fixation pathway
CCMs elevate intracellular CO2 to enhance autotrophic carbon fixation.
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DOI:10.1128/aem.01557-23
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carboxysome
contains
RuBisCO
Carboxysomes encapsulate RuBisCO to concentrate CO2 around the carboxylating enzyme.
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DOI:10.1111/ppl.14140
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carboxysome
contains
carbonic anhydrase
Carboxysomes house carbonic anhydrase alongside RuBisCO.
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DOI:10.1128/aem.01075-24
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carbonic anhydrase
converts
carbon dioxide
Carbonic anhydrase converts bicarbonate to CO2 for RuBisCO fixation.
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DOI:10.1128/aem.01075-24
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Wood-Ljungdahl pathway
example of
CO2-fixation pathway
rdfs:subClassOfThe Wood-Ljungdahl pathway is an autotrophic CO2-fixation pathway producing acetyl-CoA.
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DOI:10.1039/D4CB00099D
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Wood-Ljungdahl pathway
has output
acetyl-CoA
RO:0002234The Wood-Ljungdahl pathway yields acetyl-CoA from fixed CO2.
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DOI:10.1039/D4CB00099D
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CO dehydrogenase/acetyl-CoA synthase (CODH/ACS)
catalyzes
Wood-Ljungdahl pathway
biolink:catalyzesCODH/ACS catalyzes the terminal acetyl-CoA-forming step of the Wood-Ljungdahl pathway.
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DOI:10.1039/D4CB00099D
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molecular hydrogen
provides reductant for
Wood-Ljungdahl pathway
H2 supplies reducing equivalents driving CO2 reduction in the Wood-Ljungdahl pathway.
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DOI:10.1039/D4CB00099D
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Provenance
- Source
- METPO (2025-11-25)
- Author
- Jed Dongjin Kim-Ozaeta
- Definition source
- DOI:10.1038/nrmicro.2016.130
Parent traits (1)
Synonyms (3)
- TT_autotroph
- autotroph
- autotrophy
kg-microbe context
Matched 1 kg-microbe node via direct_metpo.
METPO:1000632[-2.568, +0.105, -3.476, -0.957, …]
Nearest neighbors in embedding space
- physiology lithotrophic 0.561
- physiology trophic type 0.440
- physiology chemolithotrophic 0.431
- physiology carboxydotrophic 0.430
- physiology chemolithoautotrophic 0.421
- physiology hydrogenotrophic 0.420
- physiology lithoautotrophic 0.419
- physiology photoorganoheterotrophic 0.402
Deep research
# Curation report: microbial trait **autotrophic** ## 1. Trait record and scope - **Trait label:** autotrophic - **Trait identifier:** **METPO:1000632** - **Category / kind / status:** PHYSIOLOGY / CLASS / REVIEWED - **Parent:** METPO:1000631 - **Synonyms:** TT_autotroph; autotroph; autotrophy ### Operational definition For TraitMech, **autotrophic** should denote an organism-level physiological capacity to grow while obtaining biomass carbon from inorganic carbon—principally CO₂ or HCO₃⁻—with energy and reducing power supplied by either light (**photoautotrophy**) or oxidation/uptake of inorganic electron donors (**chemolithoautotrophy**). Claassens et al. explicitly define autotrophs as organisms requiring “only CO₂ as a carbon source for growth” and state that microbial autotrophs derive energy from light or inorganic electron donors. Thus, the terminal phenotype should be **growth/biomass production from inorganic carbon**, not merely expression of a carboxylase or detectable CO₂ incorporation. (claassens2016harnessingthepower pages 1-2) The supplied definition is therefore current and suitable, with one practical refinement: assays may provide HCO₃⁻ rather than gaseous CO₂, and a valid demonstration should show that inorganic carbon supplies essentially all net biomass carbon under the tested condition. ### Boundary cases 1. **Carbon fixation is not equivalent to autotrophy.** Heterotrophs routinely incorporate inorganic carbon through anaplerotic and biosynthetic carboxylation. Estimated inorganic-carbon contributions are commonly 1–8% of heterotrophic microbial biomass; the broader review estimates at least 1–5%, and as much as 50% in methanotrophs. Such incorporation must not be curated as autotrophy without inorganic-carbon-supported growth. (braun2021reviewsandsyntheses pages 1-2) 2. **Mixotrophy is distinct.** Concurrent use of organic and inorganic carbon is mixotrophy, even when an autotrophic fixation pathway operates. A strain capable of both modes may receive the autotrophic trait only when growth is demonstrated under an inorganic-carbon-only condition. (claassens2016harnessingthepower pages 1-2) 3. **Photoautotrophy and chemolithoautotrophy are child mechanisms, not synonyms for the entire trait.** Phototrophy describes energy acquisition and does not by itself establish the carbon source; similarly, oxidation of H₂, sulfur, Fe²⁺, NH₃, or extracellular minerals does not establish autotrophy unless coupled to net inorganic-carbon assimilation. 4. **Genomic potential is weaker than phenotype.** A MAG containing Rubisco, CODH/ACS, or another pathway should support a candidate mechanism or “autotrophic potential,” not a definitive organismal trait, unless expression, isotope incorporation, or growth data are available. The 2024 deep-aquifer study, for example, reports genes for autotrophic pathways in 60% of MAGs but properly interprets these as chemosynthetic capacity. (atencio2024metabolicadaptationsunderpin pages 1-2) 5. **Methanotrophy and methylotrophy are generally not autotrophy.** CH₄ and methanol are organic C₁ carbon sources. Auxiliary CO₂ assimilation does not change that classification. 6. **Carbon-concentrating mechanisms are enabling modules, not universal requirements.** Carboxysomes are central to cyanobacterial and some bacterial CBB systems, but autotrophs using Wood–Ljungdahl, rTCA, 3HP, or archaeal cycles need not possess them. (pulsford2024cyanobacterialαcarboxysomecarbonic pages 1-2) ## 2. Candidate graph nodes Only identifiers that can be stated confidently are proposed. Label-only nodes should remain ungrounded until checked against the project’s preferred ontology release. ### A. Trait and biological-process nodes | Candidate node | Suggested grounding | Curation role | |---|---|---| | autotrophic | **METPO:1000632** | Terminal phenotype | | carbon fixation | GO:0015977 | General inorganic-carbon assimilation process | | Calvin–Benson–Bassham cycle | label-only; verify MetaCyc/KEGG pathway identifier | Dominant cyclic fixation module | | Wood–Ljungdahl pathway / reductive acetyl-CoA pathway | label-only; verify MetaCyc identifier | Linear anaerobic fixation module | | reductive TCA cycle | label-only | Fixation module | | 3-hydroxypropionate bicycle | label-only | Fixation module | | 3-hydroxypropionate/4-hydroxybutyrate cycle | label-only | Archaeal fixation module | | dicarboxylate/4-hydroxybutyrate cycle | label-only | Archaeal fixation module | | reductive glycine pathway | label-only | Natural/synthetic C₁ assimilation candidate | | cyanobacterial carbon-concentrating mechanism (CCM) | label-only | Carbon acquisition and concentration module | | oxygenic photosynthesis | GO term should be release-verified | Light-energy module | | extracellular electron uptake | label-only | Alternative electron-acquisition module | A recent review lists CBB, Wood–Ljungdahl, rTCA, 3HP, 3HP/4HB, DC/4HB, reductive glycine, and reverse oxidative TCA mechanisms, but pathway counts and whether the last two qualify as established natural *autotrophic growth* cycles vary among reviews. The safest core graph should begin with the six canonical pathways and add newer routes only with organism-level growth evidence. (li2024processstudyon pages 1-2, li2024productionofsuccinate pages 1-2) ### B. Chemicals, energy sources, and environmental nodes | Candidate node | Suggested grounding | Role | |---|---|---| | carbon dioxide | CHEBI:16526 | Inorganic carbon substrate | | hydrogencarbonate/bicarbonate | CHEBI:17544 | Inorganic carbon substrate and CCM pool | | dioxygen | CHEBI:15379 | Photosynthetic product, Rubisco competitor, electron acceptor, and pathway constraint | | water | CHEBI:15377 | Oxygenic photosynthesis/CA substrate | | ATP | CHEBI:15422 | Energy currency for fixation and transport | | NADPH | CHEBI:16474 | Reducing power for CBB and biosynthesis | | molecular hydrogen | CHEBI identifier should be release-verified | Common chemolithotrophic electron donor | | reduced sulfur compounds; Fe²⁺; ammonia; nitrite; phosphite | label-only pending exact species | Taxon-specific inorganic electron donors |
Curation history
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SEEDED_FROM_METPO · seed_from_metpo
imported from data/raw/metpo.owl (CLASS)
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ADDED_CAUSAL_GRAPH · codex
Added DOI-backed causal graph for inorganic carbon fixation, Calvin-Benson cycle, RuBisCO, precursor metabolites, and biomass formation.
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ADDED_ORGANISM_EXAMPLE · claude
Added Synechocystis sp. PCC 6803 organism example with PMID-backed evidence.
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GROUND_CAUSAL_PREDICATES · claude
Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000006×1, METPO:2000202×1).
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GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:catalyzes×1).
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GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (rdfs:subClassOf×1).
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GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007404×1).
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RENAME_PREDICATE_LABELS · claude
Renamed 1 causal-edge predicate label(s) to align with existing groundings: drives → regulates ×1.
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GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002211×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0019253×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (METPO:1007501×1).
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RETYPE_CAUSAL_NODES · claude
Re-typed 1 causal-node node_type field(s) to align with CausalNodeTypeEnum semantics: biomass: BIOLOGICAL_PROCESS → CHEMICAL ×1.
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0015977×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:A0A075WF79×1).
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GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:part_of×1).
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ENRICH_CAUSAL_GRAPH · claude
Added 9 evidence-backed generic edges (9 new nodes) from the deep-research report.
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GROUND_CAUSAL_PREDICATES · claude
Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (rdfs:subClassOf×1, METPO:2000202×1, biolink:catalyzes×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0030634×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0031470×1).
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GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:A0A009PMS8×1).
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RETRACT_DEAD_UNIPROT_GROUNDINGS · claude
Retracted 2 UniProtKB grounding(s) whose accessions are deleted from UniProt; nodes demoted to label-only pending re-grounding (docs/GROUNDING_POLICY.md)
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GROUND_CAUSAL_NODES · claude
Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (InterPro:IPR033966×1, InterPro:IPR001765×1).
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MIGRATE_MICROBE_DOMAIN_EDGES · claude
Re-grounded 3 causal edge(s) off microbe-domain METPO predicates (1 to has carbon source, 2 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.