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pH growth preference

METPO:1003000 · CLASS · REVIEWED

A phenotype that describes how the rate and extent of population growth are affected by environmental pH.

Environmental pH control of growth preference

Evidence-backed causal sketch linking environmental pH, pH sensing, and cytoplasmic pH homeostasis to growth preference phenotypes.

Environmental pH control of growth preference Interactive directed graph showing evidence-backed causal relationships for pH growth preference.

Edge evidence

  • environmental pH regulates pH growth preference RO:0002211

    Environmental pH determines which pH conditions support growth.

    • DOI:10.1038/nrmicro2549 tolerate or grow at external pH values Review frames pH growth as a response to external pH outside the cytoplasmic range.
  • acidic external pH challenges cytoplasmic pH homeostasis METPO:2007406

    Acidic environments impose inward proton stress that must be managed for growth.

    • DOI:10.1038/nrmicro2549 acid challenge conditions include increased expression and activity Supports active mechanisms under acid challenge.
  • alkaline external pH challenges cytoplasmic pH homeostasis METPO:2007406

    Alkaline environments require active proton accumulation or generation to maintain cytoplasmic pH.

    • DOI:10.1038/nrmicro2549 active proton accumulation or generation in the cytoplasm Supports alkaline-pH homeostasis as a growth-enabling process.
  • pH sensing regulates cytoplasmic pH homeostasis RO:0002211

    pH-sensing and signalling systems regulate homeostasis responses to acid or alkali.

    • DOI:10.1038/nrmicro2549 pH-sensing and signalling capabilities Supports regulatory sensing as part of homeostasis.
  • cytoplasmic pH homeostasis confers pH growth preference METPO:2007700

    Growth at preferred pH depends on maintaining intracellular pH compatible with cellular processes.

    • DOI:10.1038/nrmicro2549 robust mechanisms for cytoplasmic pH homeostasis Supports cytoplasmic pH homeostasis as central to growth under pH stress.
  • proton-translocating F1F0-ATPase contributes to cytoplasmic pH homeostasis RO:0002326

    The proton-translocating F1F0-ATPase mediates pH homeostasis supporting growth under low pH.

    • DOI:10.1093/femsre/fuad062 pH homeostasis mediated by the proton-translocating F1F0-ATPase; general across taxa.
  • acidic external pH induces amino-acid decarboxylase systems

    Low external pH induces amino-acid decarboxylase systems that consume protons.

    • DOI:10.1093/femsre/fuad062 amino-acid decarboxylase systems (GAD, agmatine/arginine decarboxylation) that consume protons and raise cytoplasmic alkalinity.
  • amino-acid decarboxylase systems enables amino-acid decarboxylation RO:0002327

    Decarboxylase systems carry out amino-acid decarboxylation.

    • DOI:10.1093/femsre/fuad062 amino-acid decarboxylase systems that consume protons and raise cytoplasmic alkalinity.
  • amino-acid decarboxylation contributes to cytoplasmic pH homeostasis RO:0002326

    Amino-acid decarboxylation consumes protons and raises cytoplasmic alkalinity, aiding pH homeostasis.

    • DOI:10.1093/femsre/fuad062 consume protons and raise cytoplasmic alkalinity.
  • Na+/H+ antiport contributes to cytoplasmic pH homeostasis RO:0002326

    Na+/H+ antiport (notably the Mrp system) is the major mechanism for alkaline pH homeostasis.

    • DOI:10.1038/nrmicro2549 Na+/H+ antiporters (notably the multicomponent Mrp system) are the major mechanism for alkaliphile pH homeostasis.
  • proton-consuming reaction genes associated with acidic external pH biolink:associated_with

    Genes for proton-consuming reactions (decarboxylases/deaminases) are consistently associated with lower pH preference.

    • DOI:10.1126/sciadv.adf8998 proton-consuming reactions (decarboxylases, deaminases) consistently associated with pH preference across environments.
  • Na+/H+ antiporter genes associated with alkaline external pH biolink:associated_with

    Na+/H+ antiporter genes (PhaGF/MnhG/MrpF/YufB) are associated with higher pH preference.

    • DOI:10.1126/sciadv.adf8998 Na+/H+ antiporters PhaGF, MnhG, MrpF, YufB associated with higher pH preference.

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.1038/nrmicro2549

Parent traits (1)

Children (9)

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

  • METPO:1003000 [-4.334, -2.942, -3.256, -1.316, …]

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/ph_growth_preference-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 pH growth preference

## Executive summary

**Target trait:** pH growth preference  
**Identifier:** **METPO:1003000**  
**Category/kind:** ENVIRONMENT / CLASS  
**Parent:** METPO:1000059  
**Working definition:** the reaction norm describing how controlled extracellular pH affects the rate and extent of microbial population growth.

The most defensible TraitMech graph should connect **external pH** to **cytoplasmic-pH and bioenergetic perturbations**, then to compensating transport, metabolism, membrane structure, and extracellular-pH modification, and ultimately to growth. It should not equate pH growth preference with acid survival, pH tolerance limits, intracellular pH, or environmental relative-abundance optima.

Recent research substantially strengthens this distinction. Ramoneda et al. define environmental pH preference as a **realized niche**—the pH of maximal relative abundance in nature—which can differ from the pH optimum measured in culture because of biotic and abiotic constraints. Their 2023 analysis covered 1,470 soil/freshwater samples spanning pH 3–10, 250,275 ASVs, and 38 bacterial phyla, but could conservatively infer preference for only 0.5–4.9% of ASVs per dataset. Thus, ecological preference is informative but is not a direct substitute for the assay-defined trait (ramoneda2023buildingagenomebased pages 1-2).

## 1. Trait scope and boundaries

### 1.1 Included phenotype

The trait should represent a quantitative growth response across a defined extracellular-pH series. Suitable observables include:

- maximum specific growth rate;
- lag duration;
- biomass or optical-density yield;
- colony-forming-unit increase;
- biofilm biomass or viable-cell accumulation;
- an explicitly fitted optimum pH and lower/upper growth limits.

The preferred graph endpoint is therefore **population growth rate/extent**, not merely expression of a stress gene or maintenance of intracellular pH.

### 1.2 Distinct nearby traits

| Nearby concept | Distinction from METPO:1003000 |
|---|---|
| **Growth optimum** | A summary point on the full pH–growth reaction norm; depends on medium, temperature, aeration, and measurement endpoint. |
| **Growth range/tolerance** | The pH interval permitting detectable net growth; it does not identify the preferred or optimal pH. |
| **Survival/acid resistance** | Persistence without net population growth. Foundational literature explicitly defines survival as subsequent growth after return to permissive pH (krulwich2011molecularaspectsof pages 1-3). |
| **Cytoplasmic pH homeostasis** | A causal capacity that can enable growth at external pH extremes, not the growth phenotype itself. Many bacterial cytoplasms are maintained around pH 7.0–7.5 (poolman2023physicochemicalhomeostasisin pages 1-2). |
| **Acid/alkaline stress response** | Molecular or transcriptional response following pH challenge; it may support survival, repair, or growth but does not itself establish preference. |
| **Environmental pH preference** | Realized ecological niche inferred from maximal relative abundance; it integrates competition and other environmental covariates and can differ from culture optimum (ramoneda2023buildingagenomebased pages 1-2). |
| **Extracellular pH modification** | An organism-driven environmental process that can feed back on growth; it is upstream of, rather than synonymous with, preference. |

A useful quantitative boundary case is *Bacillus pseudofirmus* OF4: it maintains cytoplasmic pH near 7.5 at external pH 7.5–9.5, grows optimally near external pH 10.5 with internal pH about 8.3, and can survive at pH ≥11 even when its cytoplasm reaches ≥9.5. These are three separable phenotypes—homeostasis, optimum growth, and survival (krulwich2011molecularaspectsof pages 12-14).

### 1.3 Assay factors that must be represented as context

Buffer concentration, buffer chemistry, carbon and nitrogen sources, sodium and potassium availability, temperature, oxygen/aeration, inoculum state, planktonic versus biofilm growth, and sampling time can alter the observed curve. In *Bacillus subtilis*, active pH regulation was visible in 1 mM MOPS but masked in standard 100 mM MOPS medium, demonstrating that buffering can remove the causal feedback being assayed (tran2024activephregulation pages 2-5, tran2024activephregulation pages 7-9).

## 2. Candidate nodes grouped by type

### Environmental and experimental nodes

- extracellular pH;
- acidic, neutral, and alkaline extracellular conditions;
- buffer capacity and buffer identity;
- oxygen availability/aeration;
- temperature;
- sodium and potassium availability;
- nutrient composition, especially amino acids and urea;
- planktonic or biofilm growth mode;
- growth rate, lag time, yield, viable-cell count, and fitted optimum pH.

Showing the first 60 of 262 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_LITERATURE · codex

    Reviewed pH growth preference trait and added DOI-backed evidence and causal graph for pH sensing and cytoplasmic pH homeostasis.

  3. · GROUND_CAUSAL_PREDICATES · claude

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

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007406×2).

  5. · GROUND_CAUSAL_NODES · claude

    Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0030641×1).

  6. · GROUND_CAUSAL_NODES · claude

    Grounded 2 causal-node grounding field(s) via mappings/node_grounding.tsv (PATO:0001428×1, PATO:0001429×1).

  7. · RENAME_PREDICATE_LABELS · claude

    Renamed 1 causal-edge predicate label(s) to align with existing groundings: influences → regulates ×1.

  8. · GROUND_CAUSAL_PREDICATES · claude

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

  9. · FIX_NODE_GROUNDING_CURIE · claude

    Overwrote 1 causal-node grounding(s) (obsolete/wrong GO -> corrected, verified vs OAK).

  10. · FIX_NODE_GROUNDING_CURIE · claude

    Overwrote 2 pH causal-node grounding(s) to corrected PATO CURIEs (phase-2; verified vs OAK).

  11. · ENRICH_CAUSAL_GRAPH · claude

    Added 7 evidence-backed generic edges (6 new nodes) from the deep-research report.

  12. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 6 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002326×3, biolink:associated_with×2, RO:0002327×1).

  13. · 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.

  14. · NORMALISE_NODE_TYPE · claude

    Under the PATHWAY-vs-BIOLOGICAL_PROCESS rule, one node_id means one thing corpus-wide (issue 356): amino_acid_decarboxylation is typed BIOLOGICAL_PROCESS. PATHWAY is a named, conventionally enumerable multi-step route; BIOLOGICAL_PROCESS is everything else. A REACTION CLASS, not a route. The corpus describes it that way in neutrophilic.yaml -- 'Enzyme-catalyzed decarboxylation reaction that consumes cytoplasmic protons' -- and the wording varies by record, so read that as the family's sense rather than as this record's own text. Named systems that implement it (Gad) would be pathways; the reaction class is not. Was 4 BIOLOGICAL_PROCESS to 2 before this tranche.