temperature delta high

Deep research

Generated by just research-trait; source: research/traits/environment/temperature_delta_high-deep-research-falcon.md

# Curation report: microbial “temperature delta high”

## Executive assessment

**Trait:** “temperature delta high”  
**Identifier:** `METPO:1000487`  
**Parent:** `METPO:1000303`  
**Category:** ENVIRONMENT; **term kind:** CLASS; **mapping:** REVIEWED  
**Operational definition:** a microbial phenotype in which reproducible growth is supported across a temperature interval, \(T_{max}-T_{min}\), greater than approximately 30°C.

The strongest exemplar recovered is *Exiguobacterium chiriqhucha* RW2, which grew from **4–50°C**, a 46°C breadth and the broadest reported range among the examined *Exiguobacterium* isolates. Its membrane phospholipid composition was measured at 4, 18, 30, and 50°C; iso-C17:1Δ5 declined from **17.0 ± 0.5 mol% at 4°C to 1.1 ± 0.3 mol% at 50°C**, a reduction exceeding 93%. This directly anchors the phenotype and strongly associates temperature-dependent membrane remodeling with it, although it does not prove that the lipid change is sufficient or necessary for the full breadth. (white2019thecompletegenome pages 17-18, white2019thecompletegenome pages 10-11, white2019thecompletegenome pages 7-9)

The best-supported mechanistic architecture is therefore **modular rather than a single pathway**:

1. low-temperature membrane sensing and homoviscous lipid remodeling;
2. RNA remodeling and maintenance of translation at the cold end;
3. chaperone/protease-mediated proteostasis and protein thermostability at the warm end;
4. possibly compatible-solute and antioxidant systems that protect membranes and macromolecules.

Only the first three have evidence strong enough to contribute selected graph edges, and even these differ substantially in evidential strength. Recent 2023 literature consolidates bacterial temperature-response mechanisms, but the search found little 2023–2024 work that directly perturbs a mechanism and demonstrates a **greater-than-30°C growth breadth**. Most recent studies address one thermal endpoint or acute survival rather than eurythermal growth. (moon2023temperaturemattersbacterial pages 7-9)

## 1. Trait scope and boundaries

### Included phenotype

A positive annotation should require:

- measured microbial growth—not merely viability—at multiple temperatures;
- documented lower and upper growth limits, or sufficient tested points to establish a breadth above approximately 30°C;
- comparable medium, pH, salinity, oxygenation, inoculum, and incubation criteria across temperatures;
- preferably serial propagation or quantitative growth curves near both endpoints.

RW2 is a strong positive example because growth was reported over 4–50°C and lipid analyses used cultures grown at 4, 18, 30, and 50°C. The strain also tolerates pH 5–11 and varying salinity, emphasizing that assay covariates must be represented separately rather than folded into the temperature trait. (white2019thecompletegenome pages 17-18, white2019thecompletegenome pages 7-9, white2019thecompletegenome pages 3-4)

### Excluded or adjacent phenotypes

- **Thermophily/hyperthermophily:** describes a high optimum or high growth range, not necessarily a range wider than 30°C. Hyperthermophilic enzymes can remain active and resist irreversible inactivation at high temperature, but that does not establish low-temperature growth.
- **Psychrophily/psychrotolerance:** establishes low-temperature growth, not a high upper limit.
- **Heat-shock or cold-shock survival:** survival after an acute exposure is not equivalent to sustained growth.
- **Thermotolerance of spores or resting states:** should not be transferred automatically to vegetative growth.
- **Broad enzyme activity range:** an isolated enzyme is not an organism-level growth phenotype.
- **Temperature optimum:** one optimum value cannot determine \(T_{max}-T_{min}\).

For example, recombinant CspL substantially improves growth at elevated temperature, but the tested spans do not establish a >30°C breadth. It is evidence for a component mechanism, not direct evidence of `METPO:1000487`. (zhou2021acoldshock pages 5-6, zhou2021acoldshock pages 1-2)

## 2. Candidate nodes and ontology grounding

Identifiers below are included only where grounding is sufficiently clear. Gene symbols, strain-specific lipids, and complexes should remain label-only until reconciled against the exact TraitMech ontology import and taxon-specific database records.

### Trait, taxa, and environmental/experimental nodes

- `METPO:1000487` — temperature delta high.
- `METPO:1000303` — supplied parent trait.
- *Exiguobacterium chiriqhucha* RW2 — exemplar taxon/strain; **label-only pending NCBITaxon verification**.
- *Bacillus subtilis* — DesK/DesR/des model organism; use a verified NCBITaxon CURIE during implementation.
- *Bacillus coagulans* 2-6 — CspL source strain; label-only pending strain-level verification.
- low temperature; high temperature; temperature downshift; heat shock; cold shock — environmental or experimental nodes; map to ENVO or assay ontology terms only after exact term verification.
- growth-supporting temperature minimum, maximum, and breadth — assay-derived quantities; preserve the temperatures, medium, atmosphere, duration, and growth criterion as evidence metadata.

### Genes, proteins, and complexes

Showing the first 60 of 211 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.