Exophiala / Hortaea: Black Yeast to Annellophores
Original bench-card visual for recognizing black yeast morphology: early annellidic budding yeast cells maturing to tapered tube-like annellophores in Exophiala and Hortaea.
Black yeast: annellidic budding maturing to tapered annellophores
Exophiala and related black yeasts start as dark budding yeast cells that reproduce by annellides, then mature into hyphae bearing tapered tube-like annellophores. The two-stage change is the teaching anchor.
Early growth shows dark yeast-like cells that bud by annellides rather than simple blastoconidia. Colonies are shiny and black at this stage.
With age, septate hyphae form annellophores that taper to a narrow tip. Clusters of oval to round conidia gather at and below the tip.
Early growth shows dark yeast-like cells that bud by annellides rather than simple blastoconidia. Colonies are shiny and black at this stage.
With age, septate hyphae form annellophores that taper to a narrow tip. Clusters of oval to round conidia gather at and below the tip.
Black yeast visual anchors
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Dark budding yeast in young culture | Annellidic yeast clue | Reproduces by annellides; shiny black colony |
| Tapered tube-like annellophores | Mature Exophiala clue | Narrowing tip with conidia clustered at the apex |
| Shift from yeast to hyphae with age | Two-stage pattern | Young yeast matures into a mold-like culture |
| Subcutaneous or skin source | Clinical context | Hortaea werneckii causes tinea nigra; interpret per SOP |
Black yeast interpretation guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Dark budding yeast maturing to annellophores | Exophiala-compatible morphology | Confirm by validated mold ID workflow |
| Tinea nigra with brown hyphae and yeast | Hortaea werneckii pattern | Correlate with superficial skin source |
| Pale budding yeast, no pigment | Not a black yeast | Reconsider Candida or Cryptococcus |
- Black yeasts shift from dark budding yeast to annellophore-bearing hyphae.
- Annellides and tapered annellophores separate them from Candida and Cryptococcus.
- Hortaea werneckii is the tinea nigra agent in this group.
Black yeast = dark annellidic buds maturing to tapered annellophores.