mycelial growth

Deep research

Generated by just research-trait; source: research/traits/morphology/mycelial_growth-deep-research-falcon.md

# Curation report: bacterial mycelial growth

## Executive summary

**Target:** `traitmech:000074` (quote verbatim)  
**Label:** mycelial growth  
**Category:** MORPHOLOGY  
**Parent:** `METPO:1000059`  
**Recommended graph scope:** the capacity of a bacterium—principally a filamentous actinomycete such as *Streptomyces*—to produce a **branched vegetative mycelium by polarized hyphal-tip extension and establishment of new lateral growth zones**. Vegetative hyphae are branched, hydrophilic, and generally multinucleoid; aerial hyphae are reproductive, comparatively unbranched and hydrophobic, and later septate into spores. Thus, aerial-hypha formation and sporulation are downstream developmental phenotypes, not necessary components of the core trait. (schlimpert2023thebestof pages 8-10, bhowmick2023osmoticstressresponses pages 1-2)

The most defensible core mechanism is:

> DivIVA-containing apical polarisome → spatial recruitment of cell-wall synthesis/remodeling machinery → polarized peptidoglycan insertion → hyphal-tip extension; budding or establishment of additional polarity centers → lateral branch formation → branched vegetative mycelium.

Recent work adds CglA-dependent cell-wall glycopolymer attachment as a determinant of normal hyphal width and branching morphology. By contrast, SepIVA localizes with DivIVA but is dispensable under the tested conditions and should not be represented as required for mycelial growth. c-di-GMP primarily controls whether *Streptomyces* remains in vegetative mycelial growth or enters aerial development; it is better modeled as a developmental-state regulator than as a direct generator of branches. (sen2024adispensablesepiva pages 1-2, gallagher2024howcdigmpcontrols pages 1-3, bhowmick2024cellshapeand pages 1-2)

## 1. Trait scope and boundaries

### Included phenotype

The trait comprises:

1. germ-tube or hyphal establishment;
2. persistent cell-wall growth at hyphal apices;
3. lateral establishment of new growth zones;
4. repeated extension and branching to form a connected vegetative filament network.

A 2024 account states that vegetative *Streptomyces* hyphae “extend by polar cell wall growth and create new growth zones by lateral branching,” while clusters of DivIVA at tips form polarisomes involved in both apical growth and de novo branch establishment. (sen2024adispensablesepiva pages 1-2)

### Excluded or separately modeled boundary cases

| Nearby phenotype | Relationship to `traitmech:000074` | Curation decision |
|---|---|---|
| Aerial-mycelium formation | Reproductive transition from vegetative growth; aerial hyphae differ in surface properties and branching pattern | Model as a downstream/alternative developmental state, not as part of the defining trait |
| Sporulation and spore-chain formation | Septation and differentiation of aerial hyphae | Exclude from the core graph; connect through developmental-transition edges if useful |
| Exploratory growth | Rapid surface expansion can involve long, relatively nonbranching vegetative hyphae after glucose depletion | Separate phenotype; it does not necessarily satisfy the branched-mycelium definition (schlimpert2023thebestof pages 8-10) |
| Linear chains of divided cells | Filamentous appearance without apical hyphal growth and lateral branching | Exclude |
| Wall-less S-cells | Vesicles extruded from tips under hyperosmotic or cell-wall stress | Stress-induced alternative morphology, not mycelial growth (schlimpert2023thebestof pages 8-10) |
| Pellets, clumps, dispersed mycelia | Macroscopic submerged-culture architectures formed by aggregation and branching | Treat as assay/bioprocess phenotypes downstream of mycelial growth, not synonyms |
| Fungal mycelium | Morphologically analogous but taxonomically and mechanistically distinct | Exclude from this bacterial trait graph |
| Filamentous cyanobacteria | Usually chains of communicating cells produced by division rather than *Streptomyces*-type polar hyphal extension | Exclude unless the trait definition is deliberately broadened |

## 2. Candidate nodes

### Trait and taxa

- `traitmech:000074` — mycelial growth.
- `METPO:1000059` — supplied parent trait.
- *Streptomyces* spp.; key experimental systems: *S. coelicolor* and *S. venezuelae*.
- *Streptomyces variegatus* — taxon used in the ROS/pyrogallol branching work.
- *Lentzea aerocolonigenes* — application-relevant filamentous actinomycete.

Taxon CURIEs should be added only after checking the current NCBI Taxonomy records for the precise strain; strain-level identifiers are not inferred here.

### Proteins and complexes

- **DivIVA** — essential polarity determinant; central polarisome scaffold.
- **Scy** — coiled-coil polarisome-associated scaffold affecting polarisome organization/branching.
- **FilP** — intermediate-filament-like protein providing mechanical organization to growing hyphae.
- **AfsK** — Ser/Thr protein kinase that phosphorylates DivIVA during cell-wall stress.

Showing the first 60 of 214 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.