temperature range low

Deep research

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

# Curation report: microbial “temperature range low”

## Executive recommendation

**Trait:** temperature range low  
**Identifier:** **METPO:1000449**  
**Parent:** METPO:1000306  
**Category/kind/status:** ENVIRONMENT / CLASS / REVIEWED

The supplied trait should be represented as an **assay-observed capacity for sustained microbial growth over an approximately 10–22 °C ambient-temperature interval**, rather than as a taxonomic assertion that an organism is obligatorily psychrophilic. The best-supported causal architecture is multifactorial: low temperature perturbs membranes, RNA folding and translation, enzyme kinetics, ice/water relations, and redox balance; organisms compensate through lipid remodeling, cold-active RNA/protein machinery, cryoprotective molecules, and stress defenses. Recent work also shows that canonical mechanisms cannot automatically be treated as necessary determinants of low-temperature growth in every organism.

The strongest perturbation evidence recovered is a taxon-specific branch in *Shewanella livingstonensis* Ac10: EPA deficiency causes growth retardation and filamentous cells at 4 °C, while EPA supplementation rescues these defects. This lies below the stated 10–22 °C band, so it supports the broader mechanism of cold growth but should not alone define METPO:1000449.

## 1. Trait scope and boundary cases

### Recommended operational interpretation

METPO:1000449 denotes a **growth-range phenotype**, requiring positive evidence of growth at multiple assay temperatures sufficient to establish that the supporting interval spans approximately 10–22 °C. “Growth” should preferably mean increasing biomass, viable counts, colony formation, or another validated reproduction measure, not merely survival or metabolic activity.

A widely used physiological definition describes psychrophiles as organisms with an optimum at or below approximately 15 °C and an upper growth limit near 20 °C. Consequently, a 10–22 °C range crosses the conventional psychrophile boundary and may also describe psychrotolerant organisms. The supplied synonyms are therefore useful search labels but are not strictly interchangeable taxonomic diagnoses (purwar2024adaptationsofpsychrophilic pages 8-10).

### Exclusions and nearby traits

* **Optimum-temperature phenotype:** An optimum at 10–22 °C does not establish that the entire range is growth-supporting.
* **Minimum growth temperature:** Growth at one low temperature does not establish a range.
* **Cold-shock response:** A transient shift, such as 37→15 °C, measures acclimation and RNA/protein stress responses rather than an evolved cardinal growth range.
* **Freeze tolerance or cryosurvival:** Viability after freezing, antifreeze activity, or ice-recrystallization inhibition does not prove growth between 10 and 22 °C.
* **Psychrophily versus psychrotolerance:** These labels depend on both optimum and maximum growth temperatures; neither should be inferred from this trait alone.
* **Cold-active enzyme phenotype:** Activity of an isolated enzyme at low temperature is mechanistically relevant but insufficient to assign the organism-level growth trait.
* **Food-refrigeration growth:** Growth at 4–7 °C is relevant supporting evidence for cold adaptation, but it is outside the nominal lower boundary and should remain assay-qualified.

## 2. Current mechanistic understanding

Low temperature tends to rigidify/thicken lipid bilayers, stabilize inhibitory RNA secondary structures, reduce reaction rates, increase oxygen solubility and associated ROS pressure, and—near or below freezing—promote damaging ice formation. Current reviews emphasize that successful cold growth is not attributable to one universal “psychrophile gene”; it is an integrated systems phenotype involving membranes, transcription/translation, protein structure, osmotic balance, and redox homeostasis (purwar2024adaptationsofpsychrophilic pages 10-11, ramon2023ageneraloverview pages 21-22).

A key expert-level qualification comes from Sidarta and colleagues’ 2024 *Bacillus subtilis* study. The canonical DesK–DesR–Des circuit was only detectably activated by a mild shift to 25 °C after 120 min (P=0.03), not by shifts to 16 or 4 °C. Moreover, *des*, *desK*, and *desR* deletion mutants lacked detectable temperature-stress growth defects under the tested conditions. The authors concluded that phase separation can impair DesK sensing and that Des-mediated fluidity changes may be too subtle to determine growth under harsh cold shock (sidarta2024lipidphaseseparation pages 5-9, sidarta2024lipidphaseseparation pages 14-16, sidarta2024lipidphaseseparation pages 1-2). Thus, membrane remodeling remains important broadly, but individual lipid-sensing circuits must be curated as taxon- and condition-specific.

## 3. Candidate nodes

Identifiers below are deliberately conservative. Gene symbols should be stored with an organism qualifier; UniProt, EC, Rhea, KEGG, or MetaCyc accessions should be added only after strain-specific verification.

### Trait and environmental nodes

| Node | Grounding | Role |
|---|---|---|
| temperature range low | **METPO:1000449** | Target phenotype |
| parent temperature-range trait | **METPO:1000306** | Ontological parent |
| ambient temperature, approximately 10–22 °C | Label-only assay node | Exposure defining the phenotype |
| low-temperature exposure/cold shock | GO:0009409, response to cold | Mechanistic experimental exposure; not equivalent to the trait |
| freezing/ice formation | Label-only environmental process | Relevant mainly below the nominal range |

### Cellular structures and processes

| Node | Suggested grounding | Role |
|---|---|---|
| plasma/cytoplasmic membrane | GO:0005886 | Primary site of lipid compensation |
| membrane fluidity | GO:0061024, membrane organization, is a broader fallback | Phenomenon requiring careful relation modeling |
| fatty-acid desaturation | GO:0006636 | Lipid-remodeling process |
| translation | GO:0006412 | Cold-sensitive process supported by ribosomal/RNA machinery |
| RNA helicase activity | GO:0003724 | Unwinds stabilized RNA structures |

Showing the first 60 of 243 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.