temperature range mid2

Deep research

Generated by just research-trait; source: research/traits/environment/temperature_range_mid2-deep-research-falcon.md

# Curation report: microbial **temperature range mid2**

## Executive assessment

**Target:** `METPO:1000451` (quoted verbatim)  
**Label:** temperature range mid2  
**Category:** ENVIRONMENT; **term kind:** CLASS; **status:** REVIEWED  
**Parent:** `METPO:1000306`  
**Synonyms:** *Mesophilie*; `TR_27_to_30`

This trait should be interpreted as an **assay-observed capacity for growth across an ambient-temperature interval whose width is approximately 27–30 °C**. It should **not** be interpreted as an optimum temperature of 27–30 °C, nor as growth exclusively between 27 and 30 °C. It is also distinct from survival after heat/cold shock, transient stress tolerance, growth rate at one temperature, or the broad informal category “mesophile.”

The strongest mechanistic graph supported by the literature is a **generic thermoadaptation module**—temperature changes membrane order, membrane sensing activates lipid remodeling, and remodeling restores physiologically useful membrane properties. However, the available evidence does **not** demonstrate that any one gene or module causes an organism’s growth-supporting interval specifically to span 27–30 °C. Consequently, mechanistic edges within the module can be curated, but the terminal edge to `METPO:1000451` should remain **uncertain/inferred** pending direct growth-range perturbation experiments.

## 1. Trait scope and boundary cases

### Positive scope

A defensible phenotype call requires growth measurements at multiple temperatures under otherwise controlled conditions. Ideally, growth-supporting lower and upper limits should be estimated using a standardized medium, atmosphere, pH, salinity, inoculum, incubation duration, and growth threshold. The approximately 27–30 °C quantity describes the **span**:

`upper growth-supporting temperature − lower growth-supporting temperature ≈ 27–30 °C`.

The exact endpoints may differ among taxa. Thus, an organism growing from 10 to 38 °C and another growing from 15 to 43 °C could both fall in this range-width class, although their optima and ecological niches differ.

### Exclusions and neighboring phenotypes

* **Temperature optimum:** a peak in growth rate or yield is not the same as the breadth of the supported interval.
* **Cardinal temperatures:** minimum, optimum, and maximum temperatures are related measurements but should be represented separately.
* **Cold/heat survival:** viability after acute exposure does not prove sustained growth.
* **Lag-phase acclimation:** recovery after a shift can reflect stress-response kinetics without changing cardinal growth limits.
* **Generic mesophily:** literature often uses “mesophilic” for optima around ordinary environmental or host temperatures; this does not establish a 27–30 °C range width.
* **Community/process temperature:** reactor performance at a “mesophilic” set point measures a community and operating regime, not necessarily a strain-level phenotype.

## 2. Current mechanistic understanding

Temperature affects membrane phase behavior, RNA structure, translation, protein folding, enzyme kinetics, and macromolecular damage. In bacteria lacking cholesterol-based thermal buffering, lower temperature promotes lipid ordering and can drive a liquid-crystalline-to-gel transition. Cis-unsaturated and anteiso-branched fatty acids disrupt tight acyl-chain packing, lower the phase-transition temperature, and support fluidity; saturated straight-chain fatty acids have the opposite tendency. This regulated remodeling is conventionally termed **homeoviscous adaptation**. (The source uses “homoviscous,” but “homeoviscous” is standard usage.) (mendoza2014temperaturesensingby pages 4-5, mendoza2014temperaturesensingby pages 2-4)

The best-resolved bacterial circuit is the *Bacillus subtilis* Des pathway. Increased membrane order changes DesK activity; DesK autophosphorylates at His-188 and transfers phosphate to DesR Asp-54; DesR-P activates `des`; and membrane-bound Δ5-desaturase introduces cis double bonds into membrane fatty acids. Importantly, membrane physical state—not temperature alone—is the proximal signal: isoleucine limitation can reduce anteiso-branched fatty acids and induce `des` at 37 °C. (mendoza2014temperaturesensingby pages 5-6)

Cold also stabilizes inhibitory RNA secondary structures and impairs ribosome biogenesis and translation. CspA acts as an RNA chaperone, while the ATP-dependent helicase CsdA supports ribosomal function. Heat causes protein unfolding and aggregation, inducing DnaK/DnaJ/GrpE, ClpB, and proteases such as Lon and FtsH. These systems plausibly help maintain growth near temperature limits, but current sources primarily establish **stress acclimation**, not causation of an exact growth-range width. (moon2023temperaturemattersbacterial pages 7-9, moon2023temperaturemattersbacterial pages 10-11, moon2023temperaturemattersbacterial pages 11-12, moon2023temperaturemattersbacterial pages 13-14)

## 3. Candidate nodes

Identifiers below are included only where confidence is high. Taxon-specific genes/proteins should ultimately be grounded to the exact strain’s UniProt or locus identifier rather than assigned a generic protein CURIE.

### Trait and environmental nodes

| Node | Suggested grounding | Role |
|---|---|---|
| temperature range mid2 | `METPO:1000451` | Target phenotype |
| parent temperature-range phenotype | `METPO:1000306` | Parent class |
| ambient temperature | label-only pending project ontology convention | Experimental/environmental variable |
| low-temperature shift | label-only | Perturbation that increases membrane order and cold responses |
| high-temperature/heat shift | label-only | Perturbation causing excess fluidity and proteotoxic stress |
| growth-supporting temperature interval | label-only | Assay-derived interval; terminal graph measurement |
| growth rate, yield, lag, viability | label-only assay nodes | Measurements needed to distinguish growth from survival |

### Cellular structures and physical states

| Node | Suggested grounding | Role |

Showing the first 60 of 267 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.