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temperature optimum high

METPO:1000447 · CLASS · REVIEWED

A temperature optimum phenotype with the best-growth ambient temperature above approximately 40 °C, characteristic of thermophilic physiology.

Temperature-optimum-high thermophile setpoint

DOI-backed graph linking thermophile membrane and protein thermostability adaptation to a temperature optimum above 40 °C.

Temperature-optimum-high thermophile setpoint Interactive directed graph showing evidence-backed causal relationships for temperature optimum high.

Edge evidence

  • hot environment selects for thermophile protein thermostability METPO:2007401

    Hot environments select for thermophile thermostable machinery.

    • DOI:10.1016/s0300-9629(97)00003-0 adapted to environments of high temperature Supports hot environments as the context for thermophile optima.
  • thermophile protein thermostability confers temperature optimum high METPO:2007700

    Thermophile thermostability yields a >40 °C optimum.

    • DOI:10.1128/MMBR.65.1.1-43.2001 resistant to irreversible inactivation at high temperatures Supports thermostability as the mechanism producing thermophile optima.
  • temperature optimum high is a temperature optimum rdfs:subClassOf

    Temperature optimum high is a quantitative bin of the temperature-optimum phenotype.

    • DOI:10.1016/s0300-9629(97)00003-0 adapted to environments of high temperature Supports the >40 °C optimum as a value within the temperature-optimum distribution.
  • reverse gyrase positively regulates positive DNA supercoiling RO:0002213

    Reverse gyrase introduces positive supercoils into DNA, a thermophile hallmark.

    • DOI:10.1264/jsme2.me23087 Reverse gyrase introduces positive supercoils into DNA and is a hallmark of many thermophiles.
  • positive DNA supercoiling decreases DNA melting at high temperature RO:0002212

    Positive supercoiling limits DNA melting and prevents thermal denaturation.

    • DOI:10.1264/jsme2.me23087 Reverse gyrase / positive supercoiling proposed to limit DNA melting and prevent thermal denaturation.
  • nucleoid-associated proteins increases genome thermostability RO:0002213

    Nucleoid-associated proteins enhance DNA/genome thermostability.

    • DOI:10.1264/jsme2.me23087 NAPs affect 3D genome organization and enhance DNA thermostability; abundance correlates with growth temperature.
  • small heat shock proteins prevents heat-induced protein aggregation RO:0002212

    Small heat shock proteins bind denaturing proteins to prevent heat-induced aggregation.

    • DOI:10.1128/mbio.03593-22 Small HSPs bind denaturing proteins and protect them from aggregation under heat stress.
  • thermosome (group II chaperonin) refolds refolding of denatured proteins

    Thermosome refolds denatured proteins in an ATP-dependent manner.

    • DOI:10.1128/mbio.03593-22 Thermosome refolds denatured proteins in an ATP-dependent manner.
  • altered membrane lipid composition stabilizes cytoplasmic membrane thermostability

    Altered membrane lipid composition stabilizes the cytoplasmic membrane at high temperature.

    • DOI:10.1128/mbio.03593-22 Heat shock leads to an altered lipid composition of the cytoplasmic membrane; unique membrane composition is a recognized thermophile adaptation.
  • hydrophobic and charged amino acid enrichment increases thermophile protein thermostability RO:0002213

    Enrichment in hydrophobic and charged amino acids increases protein thermostability.

    • DOI:10.1128/mbio.02174-23 Thermophiles show enrichment in hydrophobic and charged amino acids contributing to intrinsic protein thermostability.

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.1016/s0300-9629(97)00003-0

Parent traits (1)

Synonyms (2)

  • Thermophile EXACT_SYNONYM · metpo.owl
  • TO_>40 RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000447 [+1.114, +1.991, -0.944, +1.377, …]

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/environment/temperature_optimum_high-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 **temperature optimum high**

**Trait:** “temperature optimum high”  
**Identifier:** **METPO:1000447**  
**Category / kind / status:** ENVIRONMENT / CLASS / REVIEWED  
**Parent:** METPO:1000304  
**Operational definition:** best-growth ambient temperature above approximately 40 °C, characteristic of thermophilic physiology.

## 1. Scope and boundaries

This trait should represent an **organism-level growth optimum**, determined from a growth-rate or biomass-yield curve across temperatures. It is not equivalent to: (i) survival after acute heat shock, (ii) maximum permissive growth temperature, (iii) heat resistance of spores or resting cells, or (iv) thermostability of an isolated protein. Those properties can be mechanistic contributors or associated phenotypes, but do not establish **METPO:1000447** by themselves.

The approximately 40 °C threshold includes moderately thermophilic organisms and creates boundary cases near 40–45 °C. Classification schemes vary: one recent synthesis subdivides thermophiles into moderate thermophiles at roughly 50–60 °C, extreme thermophiles at 60–80 °C, and hyperthermophiles at 80–110 °C. These narrower labels should not replace the supplied METPO cutoff (pandey2026extremethermalenvironments pages 5-6).

A robust annotation should therefore record: medium composition, pH, oxygen/electron donor and acceptor, pressure, salinity, temperature spacing, growth metric, replicate number, and fitted optimum. This matters because temperature optimum is conditional: changing salinity, pressure, pH, or substrate can shift apparent growth performance.

### Closely related but distinct traits

- **Thermotolerance/heat resistance:** survival or retained growth after supra-optimal heat exposure. For example, an *E. coli* screen at 47 °C identified high-temperature survival genes, but *E. coli* remains mesophilic; those results support generic heat-damage mechanisms, not a thermophilic optimum (murata2011molecularstrategyfor pages 1-2).
- **Protein thermostability:** resistance of a protein to irreversible inactivation. It is a molecular property and plausible enabling mechanism, not an organismal optimum.
- **Hyperthermophily:** a narrower high-temperature class, commonly associated with optima ≥80 °C. Reverse gyrase evidence below is strongest in this range and should not be generalized automatically to organisms with optima of 41–60 °C.
- **High maximum growth temperature:** an organism may grow weakly at a high temperature while having a lower optimum.
- **Acclimation:** reversible lipid, solute, or expression changes after a temperature shift; distinct from the evolved trait setpoint.

## 2. Mechanistic model and candidate nodes

The current understanding is **multifactorial**. High-temperature growth requires maintenance of macromolecular structure, DNA topology and repair, membrane permeability, translation/protein quality control, and energy balance. No single mechanism is universal across Bacteria and Archaea.

### Environmental and assay nodes

- high ambient temperature / cultivation temperature
- temperature gradient assay
- optimal growth temperature
- supra-optimal heat stress
- pH, salinity, hydrostatic pressure, oxygen concentration
- electron-donor and electron-acceptor availability
- specific growth rate and maximum cell density
- target trait: **METPO:1000447**

### Organisms and taxonomic contexts

- *Pyrococcus furiosus* — hyperthermophilic archaeon; direct reverse-gyrase and compatible-solute experiments
- *Thermococcus kodakarensis* — hyperthermophilic archaeal genetic model
- *Saccharolobus islandicus* and *Sulfolobus acidocaldarius* — thermoacidophilic archaeal membrane models
- *Thermus thermophilus* — extreme-thermophile bacterial model
- *Escherichia coli* — mesophilic heat-stress comparator, **not** direct evidence for thermophile optimum
- *Kluyveromyces marxianus* — thermotolerant yeast engineering context

Use NCBITaxon identifiers only after strain/species verification in the source. A broad node such as **NCBITaxon:2157** (Archaea) is safe but less informative than source-specific organism nodes.

### Genes, proteins, and complexes

- **reverse gyrase / rgy** — ATP-dependent topoisomerase and DNA-binding heat-protective factor; exact UniProt accession is strain-specific
- **GrsA and GrsB** — radical-SAM GDGT ring synthases; label-only until organism-specific protein accessions are verified
- **DnaK/DnaJ/GrpE**, **GroEL/GroES**, archaeal thermosome/chaperonin
- **ClpB/ClpG**, Lon, HslUV, FtsH, DegP — disaggregation/proteolysis modules
- **Phr** — archaeal heat-response transcriptional regulator implicated in DIP-pathway regulation
- **MPGS** — mannosyl-3-phosphoglycerate synthase
- **IPCT/DIPPS** — enzymes used in di-myo-inositol-phosphate biosynthesis
- DNA repair, tRNA modification, translation-control, and cell-division systems identified in high-temperature screens

Showing the first 60 of 248 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.

Curation history

  1. · SEEDED_FROM_METPO · seed_from_metpo

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

  2. · CURATED_CAUSAL_GRAPH · claude

    Added DOI-backed definition and causal graph linking thermophile thermostability to the temperature-optimum-high bin.

  3. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×1, rdfs:subClassOf×1).

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007401×1).

  5. · ENRICH_CAUSAL_GRAPH · claude

    Added 7 evidence-backed generic edges (12 new nodes) from the deep-research report.

  6. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 4 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×2, METPO:2000017×1, RO:0002212×1).

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:A0A088E825×1).

  8. · RETRACT_DEAD_UNIPROT_GROUNDINGS · claude

    Retracted 1 UniProtKB grounding(s) whose accessions are deleted from UniProt; nodes demoted to label-only pending re-grounding (docs/GROUNDING_POLICY.md)

  9. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0160097×1).

  10. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×1).

  11. · MIGRATE_MICROBE_DOMAIN_EDGES · claude

    Re-grounded 1 causal edge(s) off microbe-domain METPO predicates (1 to confers), 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. · MIGRATE_MICROBE_DOMAIN_EDGES_PART2 · claude

    Re-grounded 1 causal edge(s) off microbe-domain METPO predicates onto their causal-graph counterparts (1 to reduces), issue 301 part 2. 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. Each replacement is a 1:1 mirror of its source predicate that changes only the domain, so the claim each edge makes is unchanged and directions are unchanged. The replacements are proposed in proposals/metpo_traitmech_v9 and are placeholder ids until METPO mints them.

  13. · REGROUND_CAUSAL_EDGE · claude

    Relabelled 1 causal edge from `reduces` to `decreases` and re-grounded it from METPO:2007802 to RO:0002212 (negatively regulates), issue 330. The corpus wrote two senses under the single label `reduces` - genuine electron donation, and a lessens/decreases sense - and METPO:2007802 is defined as donating electrons to the object and lowering its oxidation state, which this edge does not assert. The two senses could not be separated mechanically because the label was identical, so they migrated together in issue 329 and were split here by reading each edge. RO:0002212 declares no rdfs:domain or rdfs:range, so this introduces no entailment of the kind issue 301 removed.