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non halophilic

METPO:1000624 · CLASS · REVIEWED

A halophily preference in which an organism does not require or prefer elevated salt concentrations for growth.

Non-halophilic salt-stress response mechanism

Evidence-backed causal sketch linking non-halophily to lack of salt requirement, high-osmolarity stress, potassium uptake, and compatible-solute protection.

Non-halophilic salt-stress response mechanism Interactive directed graph showing evidence-backed causal relationships for non halophilic.

Edge evidence

  • low-to-moderate salinity confers non halophilic METPO:2007700

    Non-halophilic organisms do not require elevated salinity for growth.

    • DOI:10.1128/AEM.01934-12 soil-dwelling bacterium Bacillus subtilis Bacillus subtilis is used here as a non-halophilic model for salt stress responses rather than salt-requiring growth.
  • high osmolarity regulates water flux across cytoplasmic membrane RO:0002211

    Hyperosmotic stress alters cellular water balance and can impair non-halophilic growth.

    • DOI:10.1128/AEM.01934-12 outflow of water, drop in turgor, and the ensuing growth arrest Supports high-osmolarity growth inhibition through water loss and turgor decrease.
  • potassium ion mitigates water flux across cytoplasmic membrane METPO:2007407

    Rapid potassium accumulation helps adjust cytoplasmic osmotic potential after osmotic upshift.

    • DOI:10.1128/AEM.01934-12 initially importing substantial amounts of potassium ions Supports potassium uptake as an initial osmotic response.
  • proline mitigates water flux across cytoplasmic membrane METPO:2007407

    Proline accumulation supports osmoadaptation under sustained high-osmolarity conditions.

    • DOI:10.1128/JB.00778-11 proline production is required Supports de novo proline synthesis in Bacillus subtilis osmotic defense.
  • compatible-solute uptake systems imports proline METPO:2007805

    Uptake systems can import osmoprotectants that relieve high osmolarity.

    • DOI:10.1128/AEM.01934-12 osmotically controlled uptake systems Supports uptake systems for compatible solutes in Bacillus subtilis.
  • proline enables tolerance of high osmolarity

    Proline acts as an osmoprotectant enabling survival or growth under salt stress without making salt a growth requirement.

    • DOI:10.1128/AEM.01934-12 proline as an osmoprotectant Supports proline-mediated protection in a non-halophilic bacterial model.
  • osmotic upshift causes water efflux and cytoplasmic volume decrease biolink:causes

    Hypertonic stress drives rapid water efflux and cytoplasmic volume/turgor decrease.

    • DOI:10.1128/mmbr.00181-23 Under hypertonic stress water exits cells within milliseconds, causing cytoplasmic volume decreases up to ~50%, a rapid fall in turgor and increased ionic strength.
  • osmotic upshift induces rapid potassium uptake

    Cells import large amounts of K+ as the primary emergency response to osmotic upshift.

    • DOI:10.1128/mmbr.00181-23 Cells commonly import large amounts of K+ during osmotic upshift; generic across non-halophilic bacteria.
  • rapid potassium uptake requires counterion balancing by L-glutamate

    Glutamate is imported or synthesized as the counterion to balance accumulated K+ and maintain electroneutrality.

    • DOI:10.1128/mmbr.00181-23 Glutamate commonly imported or synthesized as the counterion to maintain electroneutrality during K+ accumulation.
  • rapid potassium uptake promotes replacement by compatible solute accumulation

    High intracellular K+/ionic strength is mitigated by secondary accumulation of neutral compatible solutes that replace K+.

    • DOI:10.1128/mmbr.00181-23 Bacteria such as E. coli and B. subtilis accumulate/synthesize neutral compatible solutes to replace K+; compatible-solute accumulation is a secondary response following primary K+ accumulation.

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.1128/AEM.01934-12

Parent traits (1)

Synonyms (1)

  • non-halophilic RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1000624 [-6.997, -46.693, +70.873, -15.746, …]

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/non_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. 
# TraitMech curation report: non-halophilic

## 1. Scope summary

**Trait:** non halophilic  
**Identifier:** **METPO:1000624**  
**Parent:** METPO:1000629  
**Definition supplied:** “A halophily preference in which an organism does not require or prefer elevated salt concentrations for growth.”

This trait should represent an **ecological/growth preference**, not merely survival under salt exposure. A non-halophile grows optimally without elevated salt, although it may possess substantial osmotic-stress defenses. Consequently:

- **Non-halophilic is not equivalent to salt-sensitive.** *Bacillus subtilis* is a non-halophilic model yet uses K⁺ accumulation, compatible-solute synthesis/import, stress-regulated transcription, and mechanosensitive channels to survive osmotic excursions. Reviews distinguish the requirement for salt from tolerance of salt. (hoffmann2016managementofosmotic pages 4-5, bremer2019responsesofmicroorganisms pages 3-5)
- **Halotolerant is a boundary case:** an organism may prefer low salt but tolerate high salt. Such an organism can remain non-halophilic under the supplied definition, provided the growth optimum—not merely the maximum tolerated concentration—is low.
- **Halophilic requires preference or requirement for elevated salt.** Salt-tolerance assays alone cannot establish that classification.
- **Salt stress and osmotic stress overlap but are not identical.** NaCl creates both hyperosmotic stress and ion-specific effects; sucrose or other nonionic osmolytes can test the osmotic component separately. The curated assay context should therefore record solute identity, concentration or water activity, medium, temperature, growth metric, and strain.
- Avoid treating a universal numerical cutoff as definitional unless TraitMech adopts a specific classification authority. Published cutoffs vary with medium and taxonomy; the most defensible annotation is based on a measured growth optimum across a salinity gradient.

## 2. Mechanistic interpretation

Non-halophily is best represented as a **composite phenotype graph** rather than as the output of one dedicated pathway. The central causal model is:

1. Elevated external NaCl increases extracellular osmolality.
2. Water exits the cell, reducing hydration and turgor and increasing macromolecular crowding.
3. A rapid emergency response transiently increases intracellular K⁺.
4. Sustained adaptation replaces excessive inorganic-ion accumulation with compatible solutes synthesized internally or imported from the environment.
5. Upon sudden osmotic downshift, mechanosensitive channels release solutes and reduce lysis risk.
6. These systems permit a non-halophile to tolerate temporary salinity without changing its low-salt growth preference. (hoffmann2016managementofosmotic pages 4-5, bremer2019responsesofmicroorganisms pages 3-5)

This is principally a **salt-out/compatible-solute strategy**, unlike obligate extreme halophiles whose proteomes and physiology can depend on sustained high intracellular salt.

## 3. Candidate nodes

### Trait, taxon, and environmental nodes

| Node | Suggested grounding | Curation note |
|---|---|---|
| non-halophilic | **METPO:1000624** | Target trait; preserve identifier verbatim. |
| *Bacillus subtilis* | **NCBITaxon:1423** | Strong model taxon, but strain should be recorded for gene/protein grounding. |
| elevated extracellular NaCl | **CHEBI:26710** | Environmental perturbation; attach concentration and medium to evidence. |
| hyperosmotic stress | **GO:0006970** for response to osmotic stress | GO term represents biological response, not the environmental condition itself. |
| osmotic upshift | Label-only candidate | Experimental process/event. |
| osmotic downshift | Label-only candidate | Distinct event activating mechanosensitive release. |
| low-salt growth optimum | Label-only candidate | Proximal assay phenotype establishing non-halophily. |

### Chemicals and physiological state nodes

| Node | Suggested grounding | Role |
|---|---|---|
| water | CHEBI identifier should be registry-validated during YAML preparation | Efflux during hyperosmotic shock; influx during downshift. |
| potassium ion | **CHEBI:29103** | Rapid emergency osmolyte/ion-homeostasis response. |
| L-proline | **CHEBI:26271** | Major synthesized/imported compatible solute in *B. subtilis*. |
| glycine betaine | **CHEBI:17750** | Imported compatible solute. |
| dimethylglycine | Label-only pending identifier validation | Imported stress protectant examined experimentally in *B. subtilis*. |
| cytoplasmic hydration | Label-only candidate | Falls after osmotic upshift. |
| turgor pressure | Label-only candidate | Perturbed by water flux; essential for growth. |
| macromolecular crowding | Label-only candidate | Increases following water loss. |
| intracellular compatible-solute pool | Label-only candidate | Mechanistically closer to protection than external solute concentration. |
| osmotic-stress tolerance | GO process can be linked through GO:0006970 | Distinguish from halophilic preference. |

### Genes, proteins, transporters, and pathways

Showing the first 60 of 194 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 Vibrio cholerae non-O1 organism example with PMID-backed evidence.

  3. · CURATED_WITH_LITERATURE · codex

    Added DOI-backed non-halophilic causal graph for salt-stress response in a non-halophilic Bacillus model, including K+ uptake, proline, and compatible-solute uptake systems.

  4. · GROUND_CAUSAL_PREDICATES · claude

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

  5. · RENAME_PREDICATE_LABELS · claude

    Renamed 2 causal-edge predicate label(s) to align with existing groundings: supports → enables ×1; drives → regulates ×1.

  6. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002327×1, RO:0002211×1).

  7. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (PATO:0001657×1).

  8. · GROUND_CAUSAL_PREDICATES · claude

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

  9. · ENRICH_CAUSAL_GRAPH · claude

    Added 4 evidence-backed generic edges (5 new nodes) from the deep-research report.

  10. · GROUND_CAUSAL_PREDICATES · claude

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

  11. · 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.

  12. · MIGRATE_MICROBE_DOMAIN_EDGES_PART2 · claude

    Re-grounded 1 causal edge(s) off microbe-domain METPO predicates onto their causal-graph counterparts (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.