temperature range mid1

Deep research

Generated by just research-trait; source: research/traits/environment/temperature_range_mid1-deep-research-falcon.md

# Curation report: microbial “temperature range mid1”

## Executive curation recommendation

**Trait:** temperature range mid1  
**Identifier:** `METPO:1000450`  
**Parent:** `METPO:1000306`  
**Supplied definition:** “A temperature range phenotype in which the growth-supporting ambient temperature range spans approximately 22–27 °C, characteristic of mesophilic physiology.”  
**Synonyms:** Mesophilie; TR_22_to_27

The most defensible core mechanism is:

> **lower ambient temperature → increased membrane lipid order → DesK kinase signaling → DesR phosphorylation → `des` transcription → Δ5-desaturase activity → more cis-unsaturated membrane fatty acids → preservation of low-temperature membrane fluidity → support of cellular physiology and growth**.

This backbone is directly established in *Bacillus subtilis*. A 2026 study—not a 2023–2024 source, but uniquely aligned with the target interval—directly measured a fluidity-homeostasis regime below 26 °C and demonstrated loss of that regime in a `Δdes` mutant. Its relevance is unusually high because the experimentally resolved transition lies inside the supplied 22–27 °C interval. However, the terminal edge from membrane fluidity to the exact ontology-level phenotype remains an inference unless matched growth curves demonstrate that perturbing the mechanism changes growth across 22–27 °C. (barbotin2026twotemperaturedependentmembrane pages 1-2)

| Priority | Candidate mechanism | Best-supported organism/temperature | Evidence strength | Curation recommendation |
|---|---|---|---|---|
| 1 | DesK/DesR → **des** (Δ5 desaturase) → increased unsaturated fatty acids → maintenance of membrane fluidity at low temperature | *Bacillus subtilis*; direct membrane-fluidity measurements across **20–37 °C**, with fluidity maintained **<26 °C**; cold shift **37→20 °C** and FA analysis after **45 min at 22 °C** (barbotin2026twotemperaturedependentmembrane pages 1-2, mendoza2014temperaturesensingby pages 5-6) | **Strong, direct, mechanistic** | **Curate now as core graph backbone** for lower-mesophile adaptation; note organism is Gram-positive and temperature window is inferred to cover **22–25 °C**, not all 27 °C. |
| 2 | Reduced anteiso-branched-chain fatty acids increases membrane order, which activates DesK/DesR and **des** transcription | *B. subtilis*; isoleucine limitation and **37 °C isothermal** manipulations affecting α-BCFAs; review of cold adaptation and long-term membrane remodeling (mendoza2014temperaturesensingby pages 5-6, barbotin2026twotemperaturedependentmembrane pages 1-2) | **Moderate, mechanistic but indirect for trait range** | **Curate with caution** as an upstream membrane-order input to DesK/DesR; mark **not directly tested at 22–27 °C** and partly inferred from composition-perturbation experiments. |
| 3 | Homeoviscous lipid remodeling with increased C16:1/C18:1 in phospholipids during cooler growth | *Acinetobacter baumannii* clinical strains; **18 °C vs 37 °C**; five of six strains increased **C16:1** at 18 °C, one strain increased **C18:1**; total UFA **60–80%** at 18 °C (dessenne2024lipidomicanalysesreveal pages 1-2, dessenne2024lipidomicanalysesreveal pages 4-8, dessenne2024lipidomicanalysesreveal pages 8-12, dessenne2024lipidomicanalysesreveal pages 2-4) | **Moderate, direct but taxon/temperature specific** | **Curate as supporting general membrane-adaptation evidence**, not as universal node logic; mark **Gram-negative, strain-specific, and outside direct 22–27 °C testing**. |
| 4 | CspA/CsdA RNA chaperone and helicase functions relieve low-temperature RNA secondary structure, support translation/ribosome recovery | *Escherichia coli*; cold-shock response literature, not trait-specific; CspA can reach **~15% of total protein synthesis** after cold shock; CsdA supports ribosome maintenance under cold shock (moon2023temperaturemattersbacterial pages 3-5, moon2023temperaturemattersbacterial pages 7-9) | **Moderate for cold stress, weak for METPO:1000450 specificity** | **Do not make core causal edge to 22–27 °C growth yet**; keep as **candidate auxiliary module** for transition into lower temperatures, flagged **cold-shock/assay-specific**. |
| 5 | Trigger factor / PPIase-assisted protein folding at low temperature | Primarily *E. coli* cold-response literature; trigger factor reported **~40-fold overexpression at low temperatures**; PPIases overexpressed to accelerate slow proline isomerization (moon2023temperaturemattersbacterial pages 7-9, moon2023temperaturemattersbacterial pages 5-6) | **Weak-to-moderate, indirect** | **Hold for later curation** unless a taxon with direct 22–27 °C growth phenotype is found; mark **not directly tested at 22–27 °C** and largely **general low-temperature adaptation**. |
| 6 | Trehalose accumulation via **otsAB** contributes to cold tolerance | *E. coli*; low-temperature response, with **otsA** mutant showing cold-shock sensitivity (moon2023temperaturemattersbacterial pages 5-6) | **Weak for this trait** | **Do not curate into core TraitMech graph yet**; possible environmental-stress support node only, clearly **cold-shock specific** and **not demonstrated for mesophilic 22–27 °C growth range**. |
| 7 | Heat-shock proteostasis network (DnaK/DnaJ, GroEL/ES, ClpB, Lon, ClpXP, FtsH, RpoH/RpoE) supports growth at elevated temperatures | *E. coli* and broad bacterial review evidence; several claims centered on **>30 °C**, heat shock, or **23–42 °C** translation behavior (moon2023temperaturemattersbacterial pages 6-7, moon2023temperaturemattersbacterial pages 5-6) | **Strong for heat stress, poor match to trait window** | **Exclude from core METPO:1000450 graph for now** except possibly as a boundary-case note distinguishing lower mesophiles from warmer mesophiles; mark **temperature-mismatch**. |
| 8 | Membrane fluidity itself as proximal physiological mediator of lower-mesophile growth | *B. subtilis* direct TIR-FCS fluidity data **20–37 °C** and general membrane-sensing review evidence (barbotin2026twotemperaturedependentmembrane pages 1-2, mendoza2014temperaturesensingby pages 5-6) | **Strong** | **Curate as central physiological state node** linking ambient temperature to cellular performance; supported as a general mediator, though exact growth-rate consequences at each point in **22–27 °C** remain partly inferred. |


*Table: This table ranks candidate mechanisms for curating METPO:1000450 by how directly they support growth in the lower-mesophile temperature window. It highlights which mechanisms are ready for core curation and which remain taxon-specific, assay-specific, or outside direct 22–27 °C testing.*

## 1. Trait scope and boundaries

### Operational interpretation

`METPO:1000450` should represent an **assay-observed temperature-range phenotype**: an organism can sustain measurable growth under the specified medium, atmosphere, pH, pressure, and incubation conditions at temperatures spanning approximately 22–27 °C. It should not automatically assert:

- that the organism’s optimum temperature is within 22–27 °C;
- that 22 °C and 27 °C are exact cardinal minimum and maximum temperatures;
- that growth is equally rapid throughout the interval;
- that transient survival following a temperature shift constitutes growth;
- or that every organism assigned the trait uses the same mechanism.

The interval straddles a mechanistically interesting boundary. Direct measurements in *B. subtilis*, *Streptococcus pneumoniae*, and *Staphylococcus aureus* found membrane fluidity maintained below 26 °C but increasing with temperature above that threshold. Thus, 22–25 °C may engage active low-temperature fluidity control, whereas 26–27 °C may fall near or above the transition in the tested Gram-positive organisms. This argues against treating the entire interval as a single uniform molecular state. (barbotin2026twotemperaturedependentmembrane pages 1-2)

### Boundary cases

1. **Psychrophile or psychrotolerant:** growth at 22 °C alone does not distinguish lower mesophily from broad cold tolerance. Cardinal-temperature or multi-point growth data are needed.
2. **Canonical mesophile with a warmer optimum:** an organism optimized at 30–37 °C may still grow at 22–27 °C. The trait describes supported range, not optimum.
3. **Cold-shock survival:** induction after a 37→20/22 °C shift supports an adaptation mechanism but is not by itself evidence of sustained growth across the complete interval.
4. **Dormancy or maintenance metabolism:** viability, respiration, or ATP maintenance without biomass increase should not satisfy a growth-range class.
5. **Assay dependence:** medium composition, oxygen, pH, inoculum history, and incubation duration can move apparent growth boundaries. The assay context should accompany the annotation.

## 2. Candidate graph nodes

### Environmental and experimental nodes

- ambient temperature, 22–27 °C — label-only range node linked to `METPO:1000450`;
- downward temperature shift / cold shock — experimental factor, not equivalent to the trait;
- ambient temperature, 20 °C, 22 °C, 26 °C, 27 °C, and 37 °C — literal measurement nodes or assay attributes;
- isoleucine availability — `CHEBI:24898` is a candidate grounding for L-isoleucine only after checking the intended ChEBI entity;

Showing the first 60 of 233 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.