Fun With Microbiology (What's Buggin' You?): June 2014

Cladosporium species Revisited (Kind Of) -A Black Mould -Hyphomycetes

This post is a bit of a revisitation to the fungus Cladosporium as I previously included the genera in a previous post on Cladophialophoraspecies. You can compare the two more thoroughly by checking out my previous post by clicking here.

Ecology: Cladosporium species are cosmopolitan saprophytic fungi found in soil, on plant debris and leaf surfaces.

Pathogenicity: Cladosporium species are generally considered to be non-pathogenic although they may be considered as possible opportunists in the severely debilitated host. Potentially pathogenic species previously included under the Cladosporium genera have recently been reassigned to the genera Cladophialophora (eg. C.bantianum, C.carrionii). Cladosporium may be encountered in the laboratory as a culture contaminant and must be distinguish from the pathogenic Cladophialophora.

Macroscopic Morphology: The rate of growth is dependent on the particular Cladosporium species and can vary from slow to moderately rapid. The isolate discussed in this post expanded in size rather slowly though it matured to produce copious amounts of conidia rather quickly (~7 days). The colony was velvety to suede-like in texture. Other sources describe Cladosporium’s texture as ranging from powdery to woolly. The colony may become slightly heaped and develop gentle folds as it ages. Colour ranges from greyish-green to olivaceous-green to brownish-black. The reverse is a dark brown to black in colour.

Cladosporium species on SAB, 15 Days at 30˚C (Nikon)

Cladosporium species on SAB, 25 Days at 30˚C (Nikon)

Microscopic Morphology: Cladosporium produces erect, dark, septate hyphae. Conidiophores are also darkly pigmented, may be septate and show tree-like branching. Fragile chains of dematiaceous blastoconidia are produced and exhibit a dark hila or scar at their point of attachment to the conidiophore or other conidia. The 1-4 celled conidia are round to oval (3 -6 µm X 4 - 12 µm) and may be smooth-walled to verrucose in surface texture. Cells on the conidiophore which bear the chains of conidia are sometimes septate and appear in the shape of a ‘shield’. These cells are also conidia but are referred to as shield cells. Chains of conidia easily disarticulate (break up) and were frustratingly difficult to document using both adhesive tape andslide culture techniques.

Cladosporium species are not thermotollerant and some species may not grow at 37˚C.

Cladosporium species produce darkly pigmented, septate, branching hyphae,

(LPCB, DMD-108, 400+10X)

Cladosporium species - Conidiophores are also darkly pigmented, may be septate and also show tree-like branching. (LPCB, DMD-108, 400+10X)

Cladosporium species - The Lactophenol cotton blue stain has taken more deeply in this preparation. Septate hyphae are clearly visible. (LPCB, DMD-108, 400X)

Cladosporium species -1-4 celled conidia are round to oval (3- 6 µm X 4-12 µm) and may be smooth-walled to verrucose in surface texture.

(LPCB, DMD-108, 1000X)

Cladosporium species -the structures are clearly evident here: septate hyphae, darkly pigmented conidiophores and oval conidia in chains.

(LPCB, DMD-108, 1000X)

Cladosporium species -as above. Younger conidiophores & conidia stain more intensely with the LPCB while the mature structures have developed the pigmentation.

(LPCB, DMD-108, 1000X)

Cladosporium species -the structures easily dis-articulate (break up) and it was difficult to keep them intact regardless of using the adhesive tape technique or slide culture technique.

Short chains of oval, pinmented, conidia are seen.

(LPCB, DMD-108, 1000X)

Cladosporium species - a closer look at the conidiophores bearing round to oval pigmented conidia.

(LPCB, DMD-108, 1000+10X)

Cladosporium species -a single conidia (conidiophore?) seen at the end of a septate hyphae.

(LPCB, DMD-108, 1000X)

Cladosporium species - a structure visible in some of the previous photos is more clearly seen in this picture. Here you can clearly see what is referred to as a "shield cell", because of its resemblance to a warrior's shield. These are conidiophores as you can clearly see chains of conidia extending from them. (LPCB, DMD-108, 1000+10X)