white pigmented

METPO:1003029 · CLASS · REVIEWED

A pigmentation phenotype in which microbial colonies or cells appear white or nonpigmented because visible chromophore accumulation is absent or low.

White pigmentation low-chromophore mechanism

Evidence-backed causal sketch linking white colony pigmentation to reduced visible pigment accumulation, staphyloxanthin biosynthesis machinery, and absence or silencing of carotenoid production in representative bacteria.

Edge evidence

crtOPQMN operon encodes staphyloxanthin biosynthesis METPO:2007813
The crtOPQMN operon encodes machinery for staphyloxanthin biosynthesis.
- DOI:10.1038/s41426-018-0078-1 controlled by the crtOPQMN operon Supports the operon as staphyloxanthin biosynthetic machinery.
staphyloxanthin biosynthesis has output staphyloxanthin RO:0002234
Staphyloxanthin biosynthesis produces the golden carotenoid pigment.
- DOI:10.1084/jem.20050846 Golden color imparted by carotenoid pigments Supports the link from carotenoid biosynthesis to visible golden pigment in S. aureus.
low visible chromophore accumulation results from reduced staphyloxanthin biosynthesis
Reduced or absent staphyloxanthin biosynthesis lowers visible pigment accumulation.
- DOI:10.2147/IDR.S49039 white-colony phenotype actually lacked the crtOPQMN operon Supports white colony phenotype when staphyloxanthin synthesis machinery is absent in a representative case.
low visible chromophore accumulation causes visible white color biolink:causes
Lack of accumulated chromophore yields a white or nonpigmented colony appearance.
- DOI:10.2147/IDR.S49039 white phenotypic variant Supports white appearance as a phenotype of low or absent visible pigment.
visible white color manifests as white pigmented METPO:2007400
Visible white colony color manifests the white-pigmented trait.
- DOI:10.2147/IDR.S49039 white phenotypic variant of Staphylococcus aureus Supports trait-level white pigmentation in a representative microbial context.
melanin biosynthesis has output melanin RO:0002234
PKS-mediated melanin biosynthesis produces the melanin chromophore.
- DOI:10.1007/s00792-024-01354-2 pks1 mutation abolishes melanization / decreased DHN melanin accumulation, establishing the PKS biosynthetic route to melanin.
reduced melanin accumulation results from reduced melanin biosynthesis
Reduced melanin biosynthesis lowers melanin chromophore accumulation.
- DOI:10.1080/21501203.2023.2249010 Knockout of PKS gene (pksA) reduced melanin production, yielding melanin-deficient cells.
reduced melanin accumulation causes visible white color biolink:causes
Loss of melanin chromophore yields a white colony surface / white cells.
- DOI:10.1080/21501203.2023.2249010 Mel- colonies are uneven with a white surface and white conidia; generic melanin-loss to white-pigment link.
SigB (sigma factor B) positively regulates staphyloxanthin biosynthesis RO:0002213
Sigma factor B positively regulates staphyloxanthin biosynthesis genes; its loss reduces pigment.
- DOI:10.1128/mbio.00346-24 SigB positively regulates genes involved in staphyloxanthin synthesis; disruptive sigB mutations give white colonies.
GlmS positively regulates SigB (sigma factor B) RO:0002213
GlmS directly upregulates sigB transcription, feeding the carotenoid-pigment regulatory cascade.
- DOI:10.1080/21505594.2024.2352476 GlmS directly upregulates sigB transcription (dual-luciferase and EMSA promoter binding); glmS knockout reduces sigB and golden pigment.

Provenance

Source: METPO (2025-11-25)
Definition source: DOI:10.2147/IDR.S49039

Parent traits (1)

pigmentation METPO:1003021

Synonyms (1)

Pigment_white RELATED_SYNONYM · metpo.owl

kg-microbe context

Matched 1 kg-microbe node via direct_metpo.

METPO:1003029 [-3.308, -1.196, -0.658, -0.965, …]

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).

morphology pigmentation 0.834
morphology pink pigmented 0.820
morphology carotenoid pigmentation 0.777
morphology cream pigmented 0.760
morphology green pigmented 0.750
morphology black pigmented 0.742
morphology red pigmented 0.727
morphology brown pigmented 0.701

Deep research

Generated by just research-trait; source: research/traits/morphology/white_pigmented-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: white pigmented microbial trait

## 1. Scope and current interpretation

**Target:** `METPO:1003029` — **white pigmented**; category **MORPHOLOGY**; term kind **CLASS**; parent `METPO:1003021`; synonym **Pigment_white**.

This trait should represent an **assay-observed achromatic or very-low-chromophore appearance of microbial colonies or cells**. Mechanistically, it is an endpoint rather than a conserved pathway: white appearance can result from deletion or reduced expression of a pigment-biosynthetic module, impaired positive regulation, chemical inhibition, lack of an inducing condition, or an organism’s constitutively low pigment output.

The strongest operational graph is therefore:

> pigment-pathway impairment or non-induction → reduced visible pigment accumulation → white/nonpigmented appearance.

The literature supports this interpretation. In *Serratia marcescens*, spontaneous nonpigmented morphotypes retain the complete `pigA–N` cluster but markedly downregulate it, demonstrating that white appearance need not imply pathway deletion. A `slyA` deletion likewise produces a white colony and loss of prodigiosin synthesis (xiang2022transcriptomicanalysisreveals pages 1-2). In *Staphylococcus aureus*, disruption of `crtN` produces low/pale pigmentation, whereas `crtMN` complementation restores visibly gold colonies, directly connecting carotenoid-pathway activity to departure from the white state (campbell2023variablestaphyloxanthinproduction pages 30-38, campbell2023variablestaphyloxanthinproduction pages 17-19).

### Boundary cases

1. **White versus nonpigmented.** These should be treated as equivalent only when white appearance is explicitly attributed to absent or low visible chromophore. White biomass caused by scattering, extracellular matrix, mineral precipitation, or an opaque medium is outside scope.
2. **Cream, beige, gray, translucent, or colorless.** These should not automatically map to `METPO:1003029`; curate only if the source equates them with white/nonpigmented or quantitatively establishes negligible pigment.
3. **Small-colony variants.** Colony size and pigmentation are independent axes. Some *S. aureus* small-colony variants lack staphyloxanthin, but “small colony” alone does not establish this trait (painter2015staphylococcusaureusadapts pages 20-23).
4. **Environmentally inducible pigmentation.** A colony may be white under one medium, temperature, illumination, oxygen level, or growth phase and pigmented under another. Assay conditions and observation time should therefore be represented in the graph or evidence annotation.
5. **Intrinsically white taxa versus white variants.** A constitutively unpigmented species-level phenotype and a white mutant of a normally colored strain share the observable endpoint but not necessarily the mechanism. Taxon and strain context are essential.
6. **Inverse evidence.** Experiments that restore or increase pigment—`crtMN` complementation, constitutive `pig` expression, phage induction, or pigment-enhancing medium—are valuable boundary evidence, but their direct endpoint is “not white.”

## 2. Candidate graph nodes

### Phenotypes and biological processes

- **white pigmented** — `METPO:1003029`
- visible pigment accumulation — label-only candidate
- reduced/absent visible chromophore accumulation — label-only candidate
- carotenoid biosynthetic process — `GO:0016117`
- staphyloxanthin biosynthesis — label-only candidate
- prodigiosin biosynthesis — label-only candidate
- oxidative-stress resistance — `GO:0006979` is a candidate for the broader response-to-oxidative-stress process; verify intended ontology granularity before curation
- neutrophil survival/opsonophagocytic-killing resistance — label-only candidates

### Genes, proteins, and regulatory modules

**In *S. aureus***

- `crtOPQMN` operon — label-only taxon-specific gene module
- `crtM`, dehydrosqualene synthase — label-only pending strain-specific UniProt/NCBI Gene grounding
- `crtN`, dehydrosqualene desaturase — label-only pending strain-specific grounding
- `crtMN` complementation construct — experimental-factor node
- `rsbU`, sigma-B regulatory phosphatase — label-only pending strain-specific grounding
- sigma factor B / SigB — protein/regulatory-factor node; use a strain-specific UniProt identifier only after selecting the reference strain
- `slyA` transcriptional regulator — label-only pending *S. marcescens* strain grounding

**In *S. marcescens***

- `pigA–N` prodigiosin-biosynthetic cluster — label-only gene-module node
- `pig` promoter — label-only regulatory-region node
- constitutive J23119 promoter replacement — experimental genetic construct
- `fliC`/flagellum-dependent χ-phage susceptibility — candidate contextual mechanism; not yet a direct white-trait edge

### Chemicals and metabolites

- staphyloxanthin — label-only candidate; do not assign an unverified ChEBI identifier
- prodigiosin — label-only candidate pending identifier verification
- farnesyl diphosphate — `CHEBI:37565`

Showing the first 60 of 215 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

2026-05-05T01:35:46.946745+00:00 · SEEDED_FROM_METPO · seed_from_metpo
imported from data/raw/metpo.owl (CLASS)
2026-05-11T19:10:00-07:00 · CURATED_WITH_LITERATURE · codex
Added DOI-backed definition and causal graph for staphyloxanthin biosynthesis machinery, low visible chromophore accumulation, and white colony appearance.
2026-05-20T03:35:31Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×1).
2026-05-20T05:49:25Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:causes×1).
2026-05-23T08:21:50Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (biolink:encodes×1).
2026-05-23T21:30:07Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 1 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2007400×1).
2026-06-14T05:51:46Z · GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:71690×1).
2026-06-23T00:00:00Z · ENRICH_CAUSAL_GRAPH · claude
Added 5 evidence-backed generic edges (5 new nodes) from the deep-research report.
2026-06-24T17:21:14Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (METPO:2000202×1, biolink:causes×1).
2026-06-24T17:21:20Z · GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (GO:0042438×1).
2026-06-24T17:23:34Z · GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (CHEBI:89634×1).
2026-06-26T07:15:20Z · GROUND_CAUSAL_NODES · claude
Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (UniProtKB:I6LB50×1).
2026-08-04T03:08:15Z · GROUND_CAUSAL_PREDICATES · claude
Grounded 2 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002213×2).
2026-08-06T01:00:00Z · 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.
2026-08-07T04:00:00Z · REGROUND_CAUSAL_EDGE · claude
Re-grounded the `encodes` edge(s) from biolink:encodes to METPO:2007813, issue 342. biolink:encodes is NOT a slot in the pinned biolink 4.4.0 model, so the CURIE resolved to nothing upstream while looking like an upstream term to anyone reading this record -- the disclaimer saying otherwise lived in mappings/predicate_grounding.tsv, which is not read at the point of use. RO:0002205 (has gene product) is the nearest real term but relates a GENE to a gene product, whereas these edges relate a gene cluster or operon to a protein complex or a biosynthetic process, which its range does not admit; that mismatch is why the coinage existed. METPO:2007813 is proposed in proposals/metpo_traitmech_v9 and is a placeholder id until METPO mints it, which puts it in the same state as the rest of that cohort rather than in a category of its own.