viable but nonculturable state

traitmech:000081 · CLASS · REVIEWED

A dormancy state in which cells remain viable and minimally metabolically active but lose the ability to grow on routine culture media, regaining culturability upon resuscitation.

Trait evidence (2)

DOI:10.1111/j.1574-6976.2009.00200.x
Oliver reviews the viable-but-nonculturable state, in which stressed cells stay viable yet unculturable until resuscitated.
DOI:10.1038/nrmicro2504
Lennon & Jones frame the VBNC state within the broader microbial dormancy seed-bank concept.

Stress-induced viable-but-nonculturable state

Evidence-backed causal sketch linking stress to a dormant viable-but-nonculturable state that resuscitates later.

MECHANISTIC · This graph represents a stress-induced VBNC program and subsequent resuscitation. The E. coli K-12 RpoS example anchors the persistence branch and does not imply that one sigma factor is the sole VBNC mechanism across taxa.

Edge evidence

environmental stress causes viable but nonculturable state biolink:causes
Stress drives cells into the viable-but-nonculturable state.
- DOI:10.1111/j.1574-6976.2009.00200.x Oliver reviews stress-induced entry into the VBNC state.
dormancy process confers viable but nonculturable state METPO:2007700
The VBNC state is a form of microbial dormancy.
- DOI:10.1038/nrmicro2504 Lennon & Jones frame VBNC within microbial dormancy.
oxidative stress / ROS accumulation promotes viable but nonculturable state RO:0002213
Oxidative stress / ROS accumulation promotes entry into the VBNC state.
- DOI:10.3390/foods12061179 Oxidative stress is a major trigger: ROS increase during VBNC entry (review across foodborne pathogens, mechanistically broad).
(p)ppGpp enhances stress resistance
(p)ppGpp accumulation enhances stress resistance during VBNC.
- DOI:10.3390/foods12061179 Accumulation of (p)ppGpp, enhancing stress resistance, supports the regulatory layer upstream of VBNC maintenance.
stress resistance contributes to viable but nonculturable state RO:0002326
Enhanced stress resistance supports maintenance of the VBNC state.
- DOI:10.3390/foods12061179 Stress resistance enhanced via (p)ppGpp underlies persistence in the VBNC state.
RpoS sigma factor required for resuscitation from VBNC
RpoS is required for resuscitation from the VBNC state.
- DOI:10.3390/microorganisms12010039 RpoS is expressed in VBNC cells and required for resuscitation; RpoS mutants fail to resuscitate.
RpoS sigma factor promotes viable but nonculturable state RO:0002213
RpoS promotes persistence and retained resuscitation competence in the E. coli VBNC state.
- DOI:10.1046/j.1462-2920.2003.00497.x rpoS mutants lost culturability earlier and retained resuscitation capability for less time The primary loss-of-function comparison supports RpoS involvement in VBNC persistence.
ATP promotes resuscitation from VBNC RO:0002213
ATP availability promotes resuscitation efficiency from VBNC.
- DOI:10.1016/j.jare.2023.08.002 Higher ATP levels correlated with higher resuscitation efficiency.
ATP drives NAD+ biosynthesis
Residual ATP drives NAD+ synthesis during the resuscitating lag phase.
- DOI:10.1016/j.jare.2023.08.002 Part of cellular ATP is consumed during the lag phase to synthesize NAD+.
NAD+ biosynthesis restores TCA cycle flux and oxidative phosphorylation
NAD+ synthesis restores TCA cycle flux and oxidative phosphorylation during resuscitation.
- DOI:10.1016/j.jare.2023.08.002 ATP-mediated NAD+ synthesis increases NAD+ availability, restoring TCA cycle flux and driving oxidative phosphorylation.

Protein and taxon examples

Graph node Protein Taxon UniProt status Role and evidence

RpoS sigma factor

Graph node	Protein	Taxon	UniProt status	Role and evidence
RpoS sigma factor	`UniProtKB:P13445` RNA polymerase sigma factor RpoS (rpoS)	Escherichia coli K-12 `NCBITaxon:83333`	`REVIEWED` retrieved 2026-08-24 · entry v207 · sequence v3	E. coli K-12 sigma-S factor whose loss shortens VBNC persistence and resuscitation competence under cold oligotrophic stress. `DOI:10.1046/j.1462-2920.2003.00497.x` rpoS mutants lost culturability earlier and retained resuscitation capability for less time The primary mutant study supports an RpoS-dependent VBNC survival phenotype in E. coli; UniProt verifies the reviewed K-12 RpoS entry.

UniProtKB:P13445
RNA polymerase sigma factor RpoS (rpoS)

Escherichia coli K-12
NCBITaxon:83333

REVIEWED
retrieved 2026-08-24 · entry v207 · sequence v3

E. coli K-12 sigma-S factor whose loss shortens VBNC persistence and resuscitation competence under cold oligotrophic stress.

DOI:10.1046/j.1462-2920.2003.00497.x rpoS mutants lost culturability earlier and retained resuscitation capability for less time The primary mutant study supports an RpoS-dependent VBNC survival phenotype in E. coli; UniProt verifies the reviewed K-12 RpoS entry.

Provenance

Identifier source: TraitMech local identifier
Definition source: DOI:10.1111/j.1574-6976.2009.00200.x

Parent traits (1)

dormancy traitmech:000080

Synonyms (1)

VBNC state RELATED_SYNONYM · DOI:10.1111/j.1574-6976.2009.00200.x

kg-microbe context

Matched 1 kg-microbe node via parent_proxy.

METPO:1000059 [-2.682, -2.070, -3.656, -0.652, …]

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).

environment cadmium tolerant 1.000
morphology sulfur globule 1.000
environment cobalt tolerant 1.000
environment copper tolerant 1.000
environment desiccation tolerant 1.000
environment piezophilic 1.000
environment obligately piezophilic 1.000
morphology gas vesicle 1.000

Deep research

Generated by just research-trait; source: research/traits/physiology/viable_but_nonculturable_state-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.

# Viable But Nonculturable (VBNC) State: Causal Graph Research Report

## Executive Summary

The viable but nonculturable (VBNC) state (traitmech:000081) is a widespread bacterial dormancy strategy in which cells remain alive, metabolically active, and potentially virulent yet fail to form colonies on routine culture media. This report synthesizes recent mechanistic evidence (prioritizing 2023–2024 sources) to support causal graph curation, identifying key molecular entities, environmental triggers, and resuscitation pathways suitable for YAML encoding in the TraitMech ontology.

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## 1. Trait Scope and Definition

### 1.1 Core Definition

The VBNC state is a dormant physiological condition where bacterial cells:

- **Lose culturability** on standard laboratory media despite remaining viable and metabolically active (pazosrojas2023theviablebut pages 1-2, prosdocimi2023cellphenotypechanges pages 1-2).
- **Retain resuscitation capacity** under favorable conditions, enabling return to a culturable state (prosdocimi2023cellphenotypechanges pages 1-2).
- **Maintain high ATP levels**, distinguishing them from dead cells where ATP rapidly decreases (pazosrojas2023theviablebut pages 11-13).
- **Exhibit reduced metabolic activity** with decreased nutrient transport and respiration rates (pazosrojas2023theviablebut pages 1-2).
- **Express genes continuously**, distinguishing VBNC from spore-forming states (pazosrojas2023theviablebut pages 1-2).

Published: Pazos-Rojas et al., *Microorganisms*, December 2023, https://doi.org/10.3390/microorganisms12010039; Prosdocimi et al., *Annals of Microbiology*, January 2023, https://doi.org/10.1186/s13213-022-01703-6.

### 1.2 Boundary Conditions

**VBNC cells differ from:**

- **Dead cells**: VBNC cells retain high ATP levels, intact membranes, and DNA; dead cells rapidly lose ATP, membrane integrity, and viability (pazosrojas2023theviablebut pages 11-13).
- **Spores**: VBNC cells continuously express genes and lack specialized spore structures; spores are dormant, dehydrated structures with minimal metabolic activity (pazosrojas2023theviablebut pages 1-2).
- **Persisters**: Both share toxin-antitoxin and stringent response pathways and ATP depletion mechanisms (yang2024resuscitationofviable pages 13-13). However, VBNC cells are induced by environmental stresses (starvation, cold, oxidative damage) and require resuscitation protocols, while persisters are antibiotic-tolerant subpopulations that revert spontaneously after antibiotic removal.
- **Obligate unculturability**: VBNC is reversible through resuscitation; obligate unculturable bacteria cannot be cultured due to unknown or syntrophic nutrient requirements.

**Experimental distinction** from moribund cells: VBNC cells remain "sterile but metabolically active" and "intact" (nystrom2003nonculturablebacteriaprogrammed pages 1-2), whereas moribund cells in the death phase will eventually lose viability.

Published: Nyström, *BioEssays*, March 2003, https://doi.org/10.1002/bies.10233.

### 1.3 Phenotypic Characteristics

**Morphology:**

- **Cell dwarfing**: Size reduction (e.g., *Campylobacter jejuni* viable cells 0.5–5 µm × 0.2–0.8 µm become ~0.5 mm diameter coccoid forms) (santos2023rolesofviable pages 4-7).
- **Cell rounding**: Transition from rod/spiral to coccus-like shapes; *Francisella tularensis* LVS becomes significantly rounder at 48+ hours (p<0.001) (cantlay2024phenotypicandtranscriptional pages 5-6).
- **Loss of flagella**: Observed in *C. jejuni* and *Vibrio* spp. (santos2023rolesofviable pages 4-7, prosdocimi2023cellphenotypechanges pages 1-2).
- **Thickened cell envelopes** and more rigid cell walls with altered peptidoglycan biosynthesis (pazosrojas2023theviablebut pages 11-13, santos2023rolesofviable pages 7-9).
- **Nucleoid compaction** into nanocrystalline or liquid crystalline structures stabilized by Dps or SASP proteins (pazosrojas2023theviablebut pages 11-13).

**Metabolic:**

- High ATP retention (pazosrojas2023theviablebut pages 11-13).
- Reduced DNA quantity (flow cytometry) (prosdocimi2023cellphenotypechanges pages 1-2).
- Altered membrane permeability and fatty acid composition (pazosrojas2023theviablebut pages 11-13).

Published: Santos et al., *Frontiers in Cellular and Infection Microbiology*, March 2023, https://doi.org/10.3389/fcimb.2023.1122450; Cantlay et al., *Frontiers in Microbiology*, February 2024, https://doi.org/10.3389/fmicb.2024.1347488.

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## 2. Candidate Causal Graph Entities

Entities are grouped by ontology class, with stable identifiers (CURIEs) where available.

### 2.1 Environmental Factors (Inducers)

Showing the first 60 of 409 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.

Vibrio vulnificus NCBITaxon:672 PMID:7618874 Canonical exemplar of the viable-but-nonculturable (VBNC) state.
Escherichia coli K-12 NCBITaxon:83333 DOI:10.1046/j.1462-2920.2003.00497.x Strain-level VBNC model paired to reviewed RpoS based on an rpoS-loss study of K-12-derived E. coli strains.

Curation history

2026-06-04T00:00:00Z · PROPOSED_FROM_RESEARCH · claude
Proposed candidate PHYSIOLOGY trait (viable but nonculturable state); sub-variant of dormancy.
2026-06-08T13:00:00Z · CURATED_CAUSAL_GRAPH · claude
Added evidence-backed causal graph (stress-induced VBNC) with GO node grounding and biolink/RO predicate groundings; promoted PROPOSED to REVIEWED.
2026-06-23T00:00:00Z · ENRICH_CAUSAL_GRAPH · claude
Added 7 evidence-backed generic edges (8 new nodes) from the deep-research report.
2026-06-24T17:21:15Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×2, RO:0002326×1).
2026-08-06T00:00:00Z · 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.
2026-08-21T08:00:00Z · NORMALISE_NODE_TYPE · codex
Tranche 5 of issue 356 settles the process/quality families and merges ids that meant the same sense: stress_resistance is QUALITY. Stress resistance here is enhanced tolerance or resistance of a cell or mature endospore, a measurable protective attribute. The nodes do not describe the general stress-response process.
2026-08-26T03:23:00Z · CURATE_PROTEIN_TAXON_EXAMPLE · 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 vbnc_stress_induced_dormancy=MECHANISTIC with scope_notes; added taxon-paired protein example(s) UniProtKB:P13445 on rpos (NCBITaxon:83333); regrounded 1 node(s) (rpos: none->InterPro:IPR012761); added 0 node(s) and 1 edge(s); added canonical example(s) NCBITaxon:83333.