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NaCl delta high

METPO:1000482 · CLASS · REVIEWED

A NaCl delta phenotype with a growth-supporting NaCl breadth above approximately 8% (w/v), characteristic of extreme-euryhaline organisms.

Trait evidence (2)

  • DOI:10.1093/femsre/fuy009
    salinity range

    Osmoadaptation review supports very wide salinity-tolerance breadths as the extreme-euryhaline phenotype.

  • DOI:10.1186/1746-1448-4-2
    cope with the high salt concentrations

    Saline-Systems review supports combined osmolyte / salt-in flexibility as the basis of very wide salinity tolerance.

NaCl-delta-high extreme-euryhaline breadth

DOI-backed graph linking maximal osmoadaptive flexibility to NaCl growth breadths exceeding 8% (w/v).

NONMECHANISTIC · This record is a quantitative measurement, interval, or bin in the environmental phenotype hierarchy; a token protein example would misrepresent the measured value as one inherited molecular mechanism.

NaCl-delta-high extreme-euryhaline breadth Interactive directed graph showing evidence-backed causal relationships for NaCl delta high.

Edge evidence

  • maximal osmoadaptive flexibility confers NaCl delta high METPO:2007700

    Maximal osmoadaptive flexibility yields an extreme NaCl-delta breadth.

    • DOI:10.1186/1746-1448-4-2 cope with the high salt concentrations Supports maximal osmoadaptive flexibility as the basis of extreme euryhalinity.
  • NaCl delta high is a NaCl delta rdfs:subClassOf

    NaCl delta high is a quantitative bin of the NaCl-delta phenotype.

  • high external salinity increases compatible-solute accumulation RO:0002213

    Rising external salinity increases intracellular compatible-solute content.

    • DOI:10.1128/aem.00145-24 Intracellular content of compatible solutes (glycine betaine, glutamate, proline) increases with rising salinity levels.
  • intracellular K+ accumulation supports salt-in osmoadaptation

    Cytoplasmic K+ accumulation supports the salt-in osmoadaptation strategy.

  • salt-in osmoadaptation associated with acidic proteome biolink:associated_with

    The salt-in strategy is associated with an acidic, low-pI proteome.

  • salinity transition across biomes drives proteome reorganization

    Salinity transitions across biomes drive proteome reorganization and pI shifts.

    • DOI:10.1126/sciadv.adg2059 Transitions accompanied by systematic changes in amino acid composition and isoelectric point distributions.
  • hybrid salt-in/salt-out osmoregulation supports survival in fluctuating salinity environment

    Hybrid salt-in/salt-out osmoregulation supports survival across fluctuating salinity.

  • hypersaline environment selects for halophilic osmoadaptation strategies METPO:2007401

    Hypersaline environments select for halophilic osmoadaptation strategies.

  • compatible-solute accumulation part of halophilic osmoadaptation strategies biolink:part_of

    Compatible-solute accumulation is one of the major halophilic osmoadaptation strategies.

    • DOI:10.1186/1746-1448-4-2 organic-solutes-in strategy The review identifies synthesis or accumulation of organic compatible solutes as a general strategy used by halophilic microorganisms.
  • salt-in osmoadaptation part of halophilic osmoadaptation strategies biolink:part_of

    Salt-in osmoadaptation is one of the major halophilic osmoadaptation strategies.

    • DOI:10.1186/1746-1448-4-2 molar concentrations of KCl The review identifies intracellular KCl accumulation as a general strategy for osmotic balance in halophilic microorganisms.
  • salt-in osmoadaptation part of hybrid salt-in/salt-out osmoregulation biolink:part_of

    The salt-in strategy is one constituent of hybrid salt-in/salt-out osmoregulation.

    • DOI:10.3389/frmbi.2023.1329925 not mutually exclusive The Dead Sea biofilm study concludes that salt-in and salt-out strategies can operate together in bacteria exposed to salinity fluctuations.
  • proteome reorganization part of halophilic osmoadaptation strategies biolink:part_of

    Long-term proteome reorganization is part of evolutionary adaptation across aquatic salinity transitions.

    • DOI:10.1126/sciadv.adg2059 isoelectric point distributions Cross-biome transitions are accompanied by systematic shifts in proteome amino-acid composition and inferred-proteome pI distributions.
  • hybrid salt-in/salt-out osmoregulation contributes to maximal osmoadaptive flexibility RO:0002326

    Combining salt-in and salt-out responses contributes to flexibility under rapid, extreme salinity changes.

    • DOI:10.3389/frmbi.2023.1329925 cope with such atypical changes The study links simultaneous ion transport and compatible-solute responses to bacteria inhabiting a rapidly fluctuating salinity environment.

Provenance

Identifier source
METPO (2026-06-12)
Definition source
DOI:10.1093/femsre/fuy009

Parent traits (1)

Synonyms (1)

  • Nad_>8 RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000482 [-0.207, -1.867, +0.267, +2.264, …]

512-dim DeepWalkSkipGramEnsmallen embedding from kg-microbe (2026-04-25).

Nearest neighbors in embedding space

Top-8 cosine-similar METPO traits from the 2026-04-25 deepwalk (512-D).

Deep research

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

Unreviewed literature output — not curated TraitMech content Ontology identifiers suggested below have not been resolved against their ontologies, and some are known to be wrong. Check any CURIE against the source before using it. 
# Curation report: NaCl delta high

**Trait:** “NaCl delta high”
**Identifier:** **METPO:1000482**
**Parent:** METPO:1000335
**Category:** ENVIRONMENT; **term kind:** CLASS; **mapping:** REVIEWED
**Operational definition:** growth-supporting NaCl breadth greater than approximately 8% (w/v), corresponding to an extreme-euryhaline phenotype.

## 1. Scope and interpretation

METPO:1000482 should represent the **width of the experimentally demonstrated NaCl growth interval**, not merely a high optimum, high maximum, survival after salt exposure, or occurrence in a hypersaline habitat. The minimum and maximum growth-supporting NaCl concentrations should ideally be measured in the same medium, temperature, pH, incubation time, and growth-detection assay. Because molarity, percent w/v NaCl, total Na+, practical salinity units (PSU), and water activity are not interchangeable, the graph should preserve the original assay units and medium composition.

The strongest illustrative phenotype is *Aspergillus sydowii*, which grows from no added NaCl to 5.13 M NaCl, although growth at saturation is weak. This is an extreme breadth rather than obligate halophily. By contrast, *Wallemia ichthyophaga* grows only from 10% to saturated NaCl (~32%); it has a large breadth but also a high lower bound and is therefore obligately halophilic. The same paper reports *Hortaea werneckii* growing from 0% to 32% NaCl, *Aureobasidium pullulans* from 0% to 17%, and *Debaryomyces hansenii* tolerating up to 24%. These examples show why breadth, minimum, maximum, and optimum should be represented separately (zajc2014osmoadaptationstrategyof pages 1-2, jimenezgomez2022survivinginthe pages 1-2).

Oren’s authoritative framework classifies extreme halophiles by salt optimum—approximately 2.5–5.2 M—rather than breadth. It also notes that organisms using organic compatible solutes often accommodate broader salt ranges than organisms whose proteins require a high-salt cytoplasm. Thus, “extreme halophile” and “extreme-euryhaline” overlap but are not equivalent (oren2008microbiallifeat pages 1-2, oren2008microbiallifeat pages 10-11).

### Boundary cases

- **Include:** reproducible vegetative growth across a NaCl interval exceeding ~8 percentage points w/v.
- **Do not infer from:** a single high-NaCl growth point, viability without growth, spore survival, environmental detection, gene presence, or predicted salt tolerance.
- **High maximum but unknown breadth:** insufficient for METPO:1000482.
- **Wide MgCl₂ range:** relevant to general osmoadaptation but not direct evidence for a specifically NaCl-defined trait.
- **PSU or total Na+ assays:** potentially supportive, but only after preserving ionic composition and avoiding unjustified conversion to NaCl w/v.
- **Obligate halophile:** may possess the trait if the measured interval is wide enough, but should additionally carry a high-minimum/NaCl-requirement phenotype.

## 2. Current mechanistic model

No single mechanism is sufficient across all taxa. The most defensible model is a coordinated system with four possible layers:

1. **Rapid ionic adjustment:** K⁺ uptake and Na⁺/H⁺, K⁺/H⁺, or multispecific antiport maintain turgor, pH, and ion homeostasis.
2. **Compatible-solute adjustment:** synthesis or uptake of ectoine, glycine betaine, proline, glutamate, glycerol, or related compounds balances osmotic pressure without imposing high ionic strength on most enzymes.
3. **Macromolecular adaptation:** acidic proteins, membrane and cell-wall remodeling, and stress-signaling networks preserve function at high salt.
4. **Energetic reconfiguration:** transport, compatible-solute synthesis, respiratory-chain alternatives, and carbon/amino-acid metabolism are reorganized to pay the energetic cost of adaptation.

The latest strong mechanistic study is Xing et al. (published 5 April 2024). *Natranaerobius thermophilus* grows at 3.1–4.9 M Na⁺ and optimally at 3.3–3.9 M; iTRAQ proteomics at 2.5, 3.1, 3.7, and 4.3 M Na⁺, ddPCR, intracellular metabolites, and K⁺ measurements supported simultaneous compatible-solute and salt-in strategies. Glycine betaine, glutamate, and proline increased with salinity, while Opu/ProU-family transporters, Na⁺/solute symporters, and Na⁺/K⁺/H⁺ transporters participated in adaptation. The median pI of upregulated proteins declined with salinity, consistent with cytoplasmic acidification (xing2024thepolyextremophilenatranaerobius pages 1-2, xing2024thepolyextremophilenatranaerobius pages 14-17).

## 3. Candidate nodes grouped by type

### Trait and assay nodes

- **NaCl delta high:** METPO:1000482.
- **NaCl delta phenotype parent:** METPO:1000335.
- Growth-supporting NaCl minimum; growth-supporting NaCl maximum; NaCl growth optimum; growth rate; biomass yield; water activity; incubation time; medium composition — retain as label-only assay nodes unless established TraitMech identifiers exist.

### Environmental and experimental factors

- Sodium chloride — **CHEBI:26710**.
- High-salinity environment; hypersaline water; brine; solar saltern — use ENVO terms only after identifier verification against the project’s ontology release.
- Water activity, temperature, pH, oxygen availability, carbon source, extracellular K⁺ availability, hypo-osmotic shock — label-only candidates are safer than unverified CURIEs.

### Chemicals and metabolites

- Sodium ion — **CHEBI:29101**.
- Potassium ion — **CHEBI:29103**.
- Chloride — **CHEBI:17996**.
- L-proline — **CHEBI:17203**.
- L-glutamate — **CHEBI:29985**.
- Glycerol — **CHEBI:17754**.
- Ectoine, hydroxyectoine, glycine betaine, trehalose, arabitol, and mannitol are strong candidate nodes, but their exact CURIEs should be resolved programmatically before YAML insertion rather than copied from memory.

Showing the first 60 of 222 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.

Canonical examples (2)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

  • Aspergillus sydowii NCBITaxon:75750 DOI:10.3389/fmicb.2022.840408 The artifact's strongest illustrative phenotype for extreme euryhalinity: grows from no added NaCl up to saturated (5.13 M) NaCl, noting growth at saturation is weak. The cited multi-omics study establishes growth at 1 M and at saturated NaCl; even that conservatively evidenced interval spans roughly 24 percentage points w/v, far above the ~8% (w/v) bin threshold.
  • Wallemia ichthyophaga NCBITaxon:245174 DOI:10.1128/aem.02702-13 Measured NaCl growth range of 10% to saturated (~32% w/v) with a 15-20% optimum, a ~22% (w/v) breadth, from the osmoadaptation study that also quantified salinity-dependent glycerol accumulation. The artifact flags the high lower bound as obligate halophily, which its own boundary rules permit alongside this trait when the measured interval is wide enough.

Curation history

  1. · SEEDED_FROM_METPO · seed_from_metpo

    imported from data/raw/metpo.owl (CLASS)

  2. · CURATED_CAUSAL_GRAPH · claude

    Added DOI-backed definition and causal graph linking maximal osmoadaptive flexibility to the extreme-euryhaline NaCl-delta bin.

  3. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×1, rdfs:subClassOf×1).

  4. · ENRICH_CAUSAL_GRAPH · claude

    Added 6 evidence-backed generic edges (11 new nodes) from the deep-research report.

  5. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×1, biolink:associated_with×1, METPO:2007401×1).

  6. · MIGRATE_MICROBE_DOMAIN_EDGES · claude

    Re-grounded 1 causal edge(s) off microbe-domain METPO predicates (1 to confers), issue 301. The previous predicates are transitively rdfs:subPropertyOf METPO:2000001, whose rdfs:domain is METPO:1000525 (microbe), so a causal-graph subject entailed that the subject IS a microbe; CausalNodeTypeEnum has no organism member, so no such edge could ever satisfy the domain. Edge directions are unchanged - this pass only relabels and re-grounds. RO:0002234 (has output) is used where the subject is an activity, since biolink gives it the domain 'biological process or activity'; the METPO replacements are proposed in proposals/metpo_traitmech_v8 and v9 and are placeholder ids until METPO mints them.

  7. · BACKFILL_CANONICAL_EXAMPLES · claude

    Added two exemplar taxa whose measured NaCl growth intervals exceed the ~8% (w/v) breadth threshold. Taxon ids resolved and label-checked against the local NCBITaxon build; references taken from this trait's own deep-research artifact. Deliberately excluded, per that artifact's own boundary rules -- Natranaerobius thermophilus and Euplaesiobystra salpumilio (breadth reported in total Na+ / PSU, where the artifact's boundary rules require "avoiding unjustified conversion to NaCl w/v"); Debaryomyces hansenii (upper tolerance only, no measured lower bound, and tolerance is not growth); Halomonas elongata and Virgibacillus dokdonensis (assay salinities and genomic osmoadaptation potential, not a reported growth interval); and Hortaea werneckii and Aureobasidium pullulans (wide ranges quoted, but the artifact attributes them only to "the same paper" and does not disambiguate which of its two co-cited sources measured them).

  8. · REVIEW_GRAPH_PROTEIN_TAXON · claude

    Backfilled provenance (review issue 517) for the codex protein-taxon review tranche of 2026-08-24/25, which shipped without a per-record event. In this record the tranche: set graph scope nacl_delta_high_extreme_euryhaline=NONMECHANISTIC with scope_notes.

  9. · CONNECT_CAUSAL_GRAPH · codex

    Connected the five source-supported osmoadaptation components to the existing extreme-euryhaline graph core (issues 426 and 183). Preserved the record as a measured NaCl growth-breadth bin; generic salt mechanisms do not directly establish the high-breadth trait, and no gene or operon was promoted to a primary entry.