TraitMech

TraitMech › ENVIRONMENT

moderately halophilic

METPO:1000623 · CLASS · REVIEWED

A halophily preference where growth and proliferation requires high levels of sodium chloride, usually above or about 0.2 M.

Moderate halophile compatible-solute mechanism

Evidence-backed causal sketch linking moderate halophily to NaCl stress and compatible-solute osmoadaptation.

Moderate halophile compatible-solute mechanism Interactive directed graph showing evidence-backed causal relationships for moderately halophilic.

Edge evidence

  • elevated NaCl causes osmotic stress biolink:causes

    Moderate NaCl elevation imposes osmotic stress that must be balanced for growth.

    • DOI:10.1371/journal.pone.0168818 cope with high salinities Halomonas elongata osmoregulation study supports high salinity as the stressor.
  • ectoine mitigates osmotic stress METPO:2007407

    Ectoine accumulation helps cells maintain osmotic balance at moderate salinity.

    • DOI:10.1371/journal.pone.0168818 synthesizes ectoine as its major compatible solute Supports ectoine as a compatible-solute mechanism in halophilic bacteria.
  • glycine betaine mitigates osmotic stress METPO:2007407

    Glycine betaine uptake can contribute to bacterial osmoprotection.

    • DOI:10.1093/femsre/fuy009 glycine betaine uptake Review supports glycine betaine transport as an osmoadaptation route.
  • ectoine confers moderately halophilic METPO:2007700

    Compatible-solute accumulation supports growth at elevated NaCl.

    • DOI:10.1371/journal.pone.0168818 allows microorganisms to cope with high salinities Supports compatible solutes as contributors to moderate halophily.
  • elevated NaCl selects for moderately halophilic METPO:2007401

    Moderate halophiles grow best under elevated salinity.

    • DOI:10.1093/femsre/fuy009 Moderately halophilic bacteria Review identifies moderate halophiles as models for bacterial osmotic adaptation.
  • osmotic stress induces compatible solute accumulation

    Osmotic stress under elevated NaCl induces accumulation of organic compatible solutes.

    • DOI:10.1128/mmbr.62.2.504-544.1998 Ventosa et al. 1998: organic compatible solutes (glycine betaine, ectoine, hydroxyectoine, amino acids) predominate in moderate halophiles.
  • EctD (ectoine hydroxylase) converts hydroxyectoine

    Ectoine hydroxylase EctD converts ectoine to hydroxyectoine, a generic ectoine-pathway step across halophiles.

    • DOI:10.1186/s12934-021-01567-6 Liu et al. 2021: EctD is the ectoine hydroxylase converting ectoine to hydroxyectoine.
  • BCCT transporters imports glycine betaine METPO:2007805

    BCCT-family carriers (BetT, BetP, OpuD) import compatible solutes such as glycine betaine.

    • DOI:10.58088/07hg-r941 Lichty 2024: BCCT carriers (e.g., BetT, BetP, OpuD) import osmoprotectants.
  • TeaABC TRAP transporter imports hydroxyectoine METPO:2007805

    TeaABC TRAP transporter imports ectoine and hydroxyectoine for osmoadaptation.

    • DOI:10.58088/07hg-r941 Lichty 2024: TRAP systems (e.g., TeaABC) import ectoine and 5-hydroxyectoine.
  • TeaABC TRAP transporter imports ectoine METPO:2007805

    TeaABC TRAP transporter imports ectoine for osmoadaptation.

    • DOI:10.58088/07hg-r941 Lichty 2024: TRAP systems (e.g., TeaABC) import ectoine and 5-hydroxyectoine.
  • salt-out (compatible-solute) strategy predominates in moderately halophilic

    The salt-out / compatible-solute strategy predominates among moderate halophiles.

    • DOI:10.3389/frmbi.2023.1329925 Ionescu et al. 2024: 'salt-out' is more common among moderate halophiles and relies on accumulation of small organic compounds.

Provenance

Source
METPO (2025-11-25)
Author
Anthea Guo
Definition source
PMID:9758852

Parent traits (1)

Synonyms (1)

  • moderate-halophilic RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000623 [-94.883, -13.167, +11.221, +70.341, …]

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/moderately_halophilic-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: moderately halophilic

**Target trait:** `METPO:1000623` (“moderately halophilic”)  
**Category:** ENVIRONMENT · **Term kind:** CLASS · **Mapping:** REVIEWED  
**Parent:** `METPO:1000629` · **Synonym:** moderate-halophilic

## 1. Scope and current interpretation

Moderate halophily is best represented as an **assay-observed requirement or preference for elevated environmental salinity that supports growth and proliferation**, rather than simply survival after salt exposure. The supplied METPO definition sets the lower boundary at “above or about 0.2 M” NaCl. Classical microbiological schemes are narrower, commonly placing moderate halophiles around **3–15% NaCl (approximately 0.5–2.5 M)**, although published boundaries vary. Consequently, the graph should record the actual NaCl concentration, medium, temperature, carbon source, growth endpoint, and whether the value is a minimum, optimum, or maximum rather than encoding one universal numerical cutoff.

*Halomonas elongata* is a strong organism-level exemplar. It thrives above 10% NaCl (about 1.7 M), while experiments have compared low, near-optimal, and high salinity at 0.17, 1.0, and 2.0 M NaCl, respectively. Its phenotype is supported by compatible-solute metabolism, ectoine recycling, ion handling, and salinity-dependent respiratory and behavioral responses—not ectoine alone. (hobmeier2022adaptationtovarying pages 2-3, hobmeier2022adaptationtovarying pages 1-2)

### Boundary cases

- **Halotolerant versus halophilic:** growth at high salt is insufficient by itself. A halotolerant organism may grow optimally without added salt; a halophile has an elevated-salinity optimum or requirement.
- **Slight versus moderate halophily:** strains near the lower cutoff require a measured growth curve. The METPO threshold near 0.2 M overlaps ranges that some traditional schemes call slight halophily.
- **Moderate versus extreme halophily:** organisms whose optimum lies at near-saturated salt should not inherit this trait merely because they also grow at intermediate NaCl.
- **Broad-range/euryhaline strains:** the trait should follow the optimum or requirement, not maximum tolerated NaCl alone.
- **Haloalkaliphiles and other polyextremophiles:** high pH, MgCl₂, temperature, or desiccation adaptations should be represented separately; they can confound attribution of growth to NaCl.
- **Osmotic stress versus ionic stress:** sucrose-induced osmolarity and NaCl exposure are not mechanistically equivalent. Na⁺/Cl⁻ homeostasis should remain distinct from generic hyperosmotic stress.

## 2. Candidate nodes

### Trait, taxon, and environmental nodes

- **moderately halophilic** — `METPO:1000623`
- **parent trait** — `METPO:1000629`
- ***Halomonas elongata*** — label plus verified NCBITaxon identifier during implementation; do not infer the identifier from memory
- ***Aquibacillus salsiterrae*, *A. albus*, *A. halophilus*** — comparative/taxon-restricted branches
- **sodium chloride** — ChEBI grounding should be registry-verified before YAML entry
- **high-NaCl environment**, **hyperosmotic stress**, **hypoosmotic shock**, **salinity-dependent growth** — label-only until exact ENVO/GO terms are verified
- **cytoplasm**, **cytoplasmic membrane**, **extracellular medium** — cellular-location nodes; use verified GO cellular-component CURIEs

### Chemicals and metabolites

- **L-aspartate**
- **L-aspartyl phosphate**
- **L-aspartate-semialdehyde**
- **L-2,4-diaminobutyrate (DABA)**
- **Nγ-acetyl-L-2,4-diaminobutyrate**
- **ectoine**
- **5-hydroxyectoine**
- **L-glutamate**
- **γ-aminobutyric acid (GABA)**
- **Na⁺, K⁺, H⁺, Cl⁻**
- **water/turgor**

All chemical CURIEs should be resolved against ChEBI in the curation environment. This report intentionally does not supply unverified numeric identifiers.

### Genes, proteins, transporters, and complexes

- **lysC** — aspartate kinase
- **asd** — aspartate-semialdehyde dehydrogenase
- **ectB** — DABA transaminase
- **ectA** — DABA acetyltransferase
- **ectC** — ectoine synthase
- **ectD** — ectoine hydroxylase; taxon-limited in the 2023 comparative study
- **TeaABC** — osmoregulated tripartite ATP-independent periplasmic/TRAP ectoine transporter
  - **teaA, teaB, teaC** subunits
  - **TeaD** regulatory/context node

Showing the first 60 of 210 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 Halomonas elongata organism example with PMID-backed evidence.

  3. · ADDED_CAUSAL_GRAPH · codex

    Added DOI-backed causal graph for moderate halophile compatible-solute osmoadaptation.

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002327×1).

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

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0006970×1).

  8. · REMOVE_REDUNDANT_SYNONYM · claude

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

  9. · ENRICH_CAUSAL_GRAPH · claude

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

  10. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000208×3).

  11. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:49432×1).

  12. · MIGRATE_ENABLES_TRAIT_EDGES · claude

    Migrated 1 causal edge(s) off enables/RO:0002327 with a TRAIT object (1 to confers), issue 302. RO:0002327 has range 'biological process or activity', which a trait (a disposition) cannot satisfy, so the previous form entailed trait is-a BiologicalProcessOrActivity. The replacements are proposed in proposals/metpo_traitmech_v8 and are placeholder ids until METPO mints them.

  13. · MIGRATE_MICROBE_DOMAIN_EDGES_PART2 · claude

    Re-grounded 3 causal edge(s) off microbe-domain METPO predicates onto their causal-graph counterparts (3 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.