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euryhaline

METPO:1000627 · CLASS · REVIEWED

A halophily preference in which an organism can tolerate a wide range of salinity conditions.

Euryhaline wide-salinity tolerance mechanism

Evidence-backed causal sketch linking euryhalinity to broad salinity ranges, osmotic imbalance, compatible solutes, and salinity-adaptation genes.

Euryhaline wide-salinity tolerance mechanism Interactive directed graph showing evidence-backed causal relationships for euryhaline.

Edge evidence

  • wide salinity range defines euryhaline METPO:2007500

    Euryhaline organisms tolerate or grow across broad salinity ranges.

    • DOI:10.5928/kaiyou.14.337 growing over a salinity range of 15% Communication proposes a quantitative characterization for euryhaline halophiles.
  • salinity gradient selects for euryhaline METPO:2007401

    Variable salinity environments select for broad salinity tolerance.

    • DOI:10.1186/s40168-024-01817-w salinity gradient of a typical short residence-time estuary Estuary metagenome study uses salinity gradients to analyze microbial salinity adaptation.
  • salinity gradient causes osmotic imbalance biolink:causes

    Movement across salinity gradients changes osmotic pressure on the cell.

    • DOI:10.1186/s40168-024-01817-w water immediately rushes into the cell Supports osmotic imbalance and water flux during salinity change.
  • compatible-solute transport imports compatible solutes METPO:2007805

    Euryhaline tolerance can use flexible uptake of osmoprotectants.

    • DOI:10.1016/j.csbj.2021.01.030 biosynthesis and/or uptake of compatible solutes Review supports compatible-solute uptake and biosynthesis as bacterial salt-stress responses.
  • compatible solutes mitigates osmotic imbalance METPO:2007407

    Compatible solutes help balance external osmotic pressure across changing salinity.

    • DOI:10.1186/1746-1448-1-5 balance external osmotic pressure Supports compatible solutes as osmolytes under salinity stress.
  • salinity-adaptation genes contributes to euryhaline RO:0002326

    Salinity-adaptation gene repertoires contribute to broad salinity tolerance.

    • DOI:10.1186/s40168-024-01817-w genes associated with microbial salinity adaptation Supports salinity-adaptation genes as contributors to microbial salinity niche breadth.
  • glycine betaine biosynthesis has output glycine betaine RO:0002234

    Choline is oxidized to glycine betaine in two steps by BetA and BetB.

    • DOI:10.3389/fmicb.2023.1192059 Choline is transformed into glycine betaine in two oxidative steps carried out by BetA (K00108) and BetB (K00130).
  • choline is precursor of glycine betaine

    Choline serves as the substrate for glycine betaine biosynthesis.

    • DOI:10.3389/fmicb.2023.1192059 Choline is transformed into glycine betaine in two oxidative steps (BetA/BetB).
  • glycine betaine mitigates osmotic imbalance METPO:2007407

    Glycine betaine accumulates as a compatible solute to balance osmotic pressure.

    • DOI:10.3389/fmicb.2023.1192059 Glycine betaine is a compatible solute used in the salt-out osmoadaptation strategy.
  • ectoine biosynthesis has output ectoine RO:0002234

    Ectoine is synthesized from L-aspartate in five steps (lysC/asd/ectB/ectA/ectC).

    • DOI:10.3389/fmicb.2023.1192059 Ectoine is obtained from L-aspartate in five steps mediated by lysC, asd, ectB, ectA, and ectC.
  • ectoine mitigates osmotic imbalance METPO:2007407

    Ectoine acts as an osmoprotective compatible solute under salinity stress.

    • DOI:10.3389/fmicb.2023.1192059 Ectoine widely implicated in halophily and salinity tolerance; protects cell components under stress.
  • mechanosensitive channels (Msc) responds to osmotic downshock

    Msc channels serve as safety valves releasing ions and organic solutes during sudden downward osmotic shocks.

    • DOI:10.3390/microorganisms12081738 Msc mechanosensitive channels serve as safety valves, allowing the rapid release of ions and organic solutes in the case of sudden downward osmotic shocks.
  • Na+/H+ antiporter exports cytoplasmic sodium ions METPO:2007804

    Na+/H+ antiporters expel sodium ions from the cytoplasm to maintain ion homeostasis.

    • DOI:10.3390/microorganisms12081738 Sodium ions are expelled from the cytoplasm, usually performed with the help of Na+/H+ antiporters.
  • proteome acidification contributes to euryhaline RO:0002326

    Acidification of the proteome improves protein solubility across salinity regimes.

    • DOI:10.1126/sciadv.adg2059 Increase in acidic amino acids (notably glutamate); acidification of the proteome essential for protein solubility at higher ionic strength.

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.5928/kaiyou.14.337

Parent traits (1)

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000627 [-3.209, -1.862, -0.407, -3.229, …]

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/euryhaline-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: microbial euryhaline trait

## Executive summary

**Trait:** euryhaline  
**Identifier:** `METPO:1000627`  
**Parent:** `METPO:1000629`  
**Definition supplied:** “A halophily preference in which an organism can tolerate a wide range of salinity conditions.”

For TraitMech, euryhaline should be represented primarily as an **assay-demonstrated capacity for growth or survival across a broad salinity interval**, rather than as one molecular pathway or a particular optimal salinity. The clearest microbial exemplar is *Chromohalobacter salexigens*: it grows at 0.1–4 M NaCl in complex medium and 0.5–3 M in minimal medium, with an optimum near 1.5 M NaCl. Thus, a euryhaline organism may still be an obligate halophile under defined conditions. Medium, temperature, acclimation, ion composition, and the endpoint measured must accompany the phenotype annotation (vargas2008unravellingtheadaptation pages 1-2).

The strongest conserved mechanistic model is biphasic: hyperosmotic exposure first causes water loss, reduced hydration and turgor, followed by rapid ion management—often K⁺ uptake and Na⁺ exclusion—and then longer-term synthesis or import of compatible organic solutes. During hypoosmotic downshift, mechanosensitive channels release cytoplasmic solutes to prevent excessive turgor and lysis. This flexible “salt-out/organic-solutes-in” strategy is particularly compatible with fluctuating salinity, although recent evidence shows that some organisms use hybrid compatible-solute plus salt-in strategies (xing2024thepolyextremophilenatranaerobius pages 1-2, czech2018roleofthe pages 3-5).

## 1. Trait scope and boundary cases

### Recommended operational interpretation

Curate `METPO:1000627` when a study reports growth, replication, metabolic activity, or survival over an explicitly broad range of salinities. Record:

- lower and upper tested limits;
- optimum and concentration units;
- salt identity or total salinity;
- complex versus defined medium;
- temperature, pH, acclimation, and exposure duration;
- whether the endpoint was growth, viability, activity, or acute-shock survival.

No universal numerical width currently defines microbial euryhalinity. A defensible annotation therefore requires comparison with the organism’s optimum, related taxa, or the source’s explicit characterization as broad/euryhaline.

### Benchmark phenotypes

*Chromohalobacter salexigens* grows over **0.1–4 M NaCl in complex medium**, but only **0.5–3 M NaCl in M63 minimal medium**, with optimum growth at approximately **1.5 M NaCl and 37°C**. This demonstrates both a broad phenotype and strong assay dependence (vargas2008unravellingtheadaptation pages 1-2).

*Halomonas elongata* can tolerate more than **5 M NaCl (approximately 30%)**. Deleting `ectA`, however, prevents growth above approximately **0.7 M NaCl**, directly connecting compatible-solute synthesis to the upper portion of its salinity range (kindzierski2017osmoregulationinthe pages 1-2).

*Spiribacter salinus* is an obligate moderate halophile: it does not grow below approximately 0.4 M NaCl, has an optimum near 0.8 M, and remains capable of progressively impaired growth through approximately 2.0 M. Euryhalinity therefore does **not** imply growth without salt (leon2018compatiblesolutesynthesis pages 4-5).

### Distinctions from adjacent traits

- **Halophily** describes a requirement or preference for elevated salinity; **euryhalinity** describes breadth of the tolerated interval. An organism can be both obligately halophilic and euryhaline.
- **Halotolerance** commonly denotes tolerance without a salt requirement. It overlaps with but is not synonymous with euryhalinity.
- **Moderate/extreme halophile** categories refer principally to optimal or required salinity, not range width.
- **Osmotolerance** is broader than salt tolerance: nonionic osmolytes can impose osmotic stress without Na⁺ or Cl⁻ toxicity.
- **Acute salt-shock survival** is not equivalent to sustained growth across salinities.
- **Salt-in strategists** maintain high intracellular inorganic-ion concentrations and acidic proteomes. Many are poorly tolerant of low salt. By contrast, compatible-solute strategists generally have greater flexibility, but this is a comparative tendency rather than a sufficient diagnostic criterion (czech2018roleofthe pages 3-5, xing2024thepolyextremophilenatranaerobius pages 24-25).

## 2. Candidate causal-graph nodes

### Trait and environmental nodes

- euryhaline — `METPO:1000627`
- broad salinity growth range — label-only assay node
- external salinity / NaCl concentration — label-only; consider an ENVO salinity-quality term only after identifier verification
- hyperosmotic upshift
- hypoosmotic downshift
- high-salinity stress
- low-salinity stress
- medium composition, temperature, pH, acclimation time, and exposure duration

### Cellular states and processes

Showing the first 60 of 252 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.

Curation history

  1. · SEEDED_FROM_METPO · seed_from_metpo

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

  2. · CURATED_WITH_ORGANISM_EXAMPLE · codex

    Added Chromohalobacter salexigens organism example with PMID-backed evidence.

  3. · CURATED_WITH_LITERATURE · codex

    Added DOI-backed euryhaline causal graph for broad salinity tolerance, salinity gradients, compatible solutes, and salinity-adaptation genes.

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002326×1).

  5. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:causes×1).

  6. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007401×1, METPO:2007407×1).

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:65015×1).

  8. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007500×1).

  9. · FIX_NODE_GROUNDING_CURIE · claude

    Overwrote 1 causal-node grounding(s) to corrected CURIEs (phase-2 id-label fix; verified vs OAK).

  10. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000208×1).

  11. · REMOVE_REDUNDANT_SYNONYM · claude

    Removed 1 synonym(s) whose text duplicated the label (seeder redundancy; no information lost).

  12. · ENRICH_CAUSAL_GRAPH · claude

    Added 8 evidence-backed generic edges (10 new nodes) from the deep-research report.

  13. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 6 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×2, METPO:2007407×2, METPO:2000209×1, RO:0002326×1).

  14. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:A0A068T423×1).

  15. · GROUND_CAUSAL_NODES · claude

    Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0031456×1, GO:0019491×1).

  16. · RETRACT_DEAD_UNIPROT_GROUNDINGS · claude

    Retracted 1 UniProtKB grounding(s) whose accessions are deleted from UniProt; nodes demoted to label-only pending re-grounding (docs/GROUNDING_POLICY.md)

  17. · MIGRATE_MICROBE_DOMAIN_EDGES · claude

    Re-grounded 2 causal edge(s) off microbe-domain METPO predicates (2 to has output), 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.

  18. · MIGRATE_MICROBE_DOMAIN_EDGES_PART2 · claude

    Re-grounded 2 causal edge(s) off microbe-domain METPO predicates onto their causal-graph counterparts (1 to exports, 1 to imports), issue 301 part 2. 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. Each replacement is a 1:1 mirror of its source predicate that changes only the domain, so the claim each edge makes is unchanged and directions are unchanged. The replacements are proposed in proposals/metpo_traitmech_v9 and are placeholder ids until METPO mints them.

  19. · NORMALISE_NODE_TYPE · claude

    Under the PATHWAY-vs-BIOLOGICAL_PROCESS rule, one node_id means one thing corpus-wide (issue 356): ectoine_biosynthesis is typed PATHWAY. PATHWAY is a named, conventionally enumerable multi-step route; BIOLOGICAL_PROCESS is everything else. A named route, enumerated two ways and both of them enumerations. environment/euryhaline.yaml counts five steps from L-aspartate (lysC/asd/ectB/ectA/ectC); environment/nacl_delta_mid1.yaml counts the three ectABC enzymes proper. Naming the file matters because the two differ and a bare quote would put euryhaline's wording into nacl_delta_mid1's record (#400 review). Either way the steps can be listed, which is the test. Applied AGAINST the majority, which was 4 BIOLOGICAL_PROCESS to 2 before this tranche.