temperature delta

Deep research

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

# Curation report: microbial temperature delta

## Executive summary

**Target:** `METPO:1000303` (“temperature delta”), an environmental class representing the numerical breadth of ambient temperatures that support microbial growth:

\[
\Delta T_{growth}=T_{max,growth}-T_{min,growth}
\]

The most defensible interpretation is an **assay-derived growth-niche breadth**, not a stress-survival phenotype. Both endpoints must be measured under specified medium, pH, atmosphere, pressure, salinity, inoculum, incubation time, and growth-detection threshold. Cardinal-temperature models treat minimum, optimum, and maximum growth temperatures as distinct parameters; the optimum is not part of the subtraction. Microbial temperature-response curves are usually asymmetric, with performance declining particularly sharply above the optimum. (noll2020modelingandexploiting pages 6-8)

Mechanistically, temperature delta is an emergent phenotype. Its lower boundary is strongly influenced by maintenance of membrane fluidity, transcription/translation at low temperature, and cold-active protein-folding systems. Its upper boundary is influenced by membrane stability, proteostasis, osmotic/ionic homeostasis, oxidative-damage control, and preservation of translation and envelope functions. The strongest direct evidence presently supports membrane-fluidity regulation and high-temperature proteostasis; many general claims about compatible solutes or cold-shock proteins concern stress survival rather than a measured change in full growth-range breadth.

## 1. Trait scope and boundary cases

### Recommended operational definition

Curate `METPO:1000303` when a study reports—or permits calculation of—the difference between the highest and lowest temperatures supporting **reproducible net growth** under the same operational criterion. Ideally, growth should be demonstrated by increasing viable counts, biomass, optical density, or another validated replication measure, rather than metabolic activity alone.

The value is conditional on the assay. A suitable evidence record should retain:

- organism and strain;
- Tmin and Tmax values and inclusivity;
- medium and nutrient composition;
- pH, salinity/water activity, oxygen or electron-acceptor conditions, and pressure;
- incubation duration and temperature resolution;
- growth threshold and replicate information;
- acclimation or evolutionary history.

The broad literature spans approximately −2 to 122°C in one cross-microbial modeling compilation, while an extremophile review describes an approximately 120°C global domain-level span. These are **across-organism envelopes**, not temperature deltas of an individual strain. (siliakus2017adaptationsofarchaeal pages 14-15, noll2020modelingandexploiting pages 6-8)

### Distinctions from nearby traits

1. **Minimum growth temperature:** one endpoint contributing to delta; it is not itself temperature delta.
2. **Maximum growth temperature:** the other endpoint; likewise not the breadth.
3. **Optimum growth temperature:** temperature yielding maximal performance. An organism can shift Topt without broadening its niche; E. coli evolution experiments have shifted optimum performance while preserving thermal breadth. (noll2020modelingandexploiting pages 6-8)
4. **Thermal performance-curve shape:** includes growth rate, skew, peak height, and activation/deactivation slopes; delta retains only the support interval.
5. **Heat-shock or cold-shock survival:** persistence after acute exposure does not establish sustained growth at that temperature. This distinction is biologically important: 2024 work in Salmonella found that greatly increased heat-shock resistance through loss of DnaJ carried poorer growth at 37°C and above, illustrating that shock resistance can move opposite to growth performance.
6. **Thermophile/psychrophile class:** an ecological preference or cardinal-temperature classification, not necessarily a broad range. Extremophiles may be specialists with narrow deltas.
7. **Acclimation/plasticity versus evolved breadth:** short-term expression or lipid remodeling may restore growth within an existing range; a heritable endpoint shift is evidence of evolved range expansion.
8. **Dormancy, spore survival, or metabolic activity without division:** exclude unless the ontology explicitly allows non-growing persistence.

A useful concrete boundary example is *Psychromonas ingrahamii*, reported with Tmin −12°C and Topt 5°C. The difference between these two values is **not** temperature delta because Tmax is absent. (siliakus2017adaptationsofarchaeal pages 8-10)

## 2. Candidate nodes grouped by type

### Trait and assay nodes

- temperature delta — `METPO:1000303`
- minimum growth temperature — retain the supplied parent `METPO:1000533` if confirmed locally
- maximum growth temperature — retain the supplied parent `METPO:1000534` if confirmed locally
- optimum growth temperature — label-only unless an existing verified METPO identifier is available
- sustained microbial growth — candidate `GO:0040007` (growth), with organismal context
- ambient temperature — candidate `ENVO:01000207` only after confirming that its intended scope fits the project
- temperature-shock survival — label-only and explicitly separate from the target

### Cellular structures and physical states

- cytoplasmic membrane

Showing the first 60 of 254 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.