Saturday 3 October 2015

Chrysosporium species

Chrysosporium species (Mould)

Note:  Chrysosporium is another species I’ve been holding onto in hopes of obtaining additional specimens (strains) and taking better photographs.  I’m really not satisfied with what I’ve taken to date but here they are for what they’re worth.

Chrysosporium is a ubiquitous, cosmopolitan fungus.  It is a rather common saprobe (living on dead organic matter).

 A number of species are keratinophiles and although they may be isolated from skin and nails, they are generally considered to be contaminants.
Rare reports of systemic infections in immunocompromised hosts have been published; however, their importance in the disease process remains uncertain.  Skin infections of snakes, iguanas, crocodiles and dogs have been more commonly reported.

Colony Morphology:
Growth is described as slow to moderately rapid, reaching maturity within about one week.
Colony morphology may be quite variable between isolated species.  Texture is powdery to cottony to woolly.  The colony may remain compact or be spreading and may show further variation by being flat or raised.  Pigmentation is usually white but may vary from pale yellow, pink, pale brown or weakly orange.  The reverse is most often white but may be yellow, tan or brownish.

 Chrysosporium species - on Saboraud Dextrose Agar (SAB), 14 days at 30ᵒC. (Nikon)

Chrysosporium species - after 21 days on SAB, at 30ᵒC. (Nikon)

Microscopic Morphology:
Chrysosporium produces septate, hyaline hyphae.  Conidia (aleurioconidia) often appear to be minimally differentiated from the hyphae and may appear to form directly on the hyphae (sessile).  Conidia more often form at the ends of simple or branched conidiophores of varying length. Conidiophores may be ramified, forming tree-like structures.  Conidia are usually one-celled (2 – 9 X 3 – 13 µm).  They appear as clavate (club shaped) with the apex (top) rounded while the base being broad and flat.  Remnants of the attaching structure may, for a time, remain attached.  Conidial walls are thin-walled and the exterior is usually smooth.  Intercalary conidia are sometimes formed and may appear as a cylindrical or barrel shaped structure or may be seen as a bulge on only one side of the hyphae.

Chrysosporium is the asexual form of Nannizziopsis vriesii and therefore ascocarps (large, sexual fruiting bodies) may occasionally be seen in fresh cultures.

Chrysosporium species - initial look at a slide culture at low power.  Can't see much detail but I just liked the look of this photo.
(250X, LPCB*, DMD-108
* Lactophenol Cotton Blue Stain

Chrysosporium species - another slide culture.  Picture a coverslip on a block of agar about a square centimeter in size.  All along the four edges of the coverslip, the fungus is growing.  Gently removing the coverslip from the agar block has some of the fungus adhering to the glass coverslip.  Placing the coverslip onto a microscope slide that has a drop of Lactophenol Cotton Blue Stain on it.  The right side of the above photo shows the edge that was against the agar block from which the fungus grew.
This slide shows the extensive branching mycelia with free and bound conida throughout.
(250X, LPCB, DMD-108)

Chrysosporium species - hyphae and conidia still attached to the conidiophores and hyphae.
(250X, LPCB, DMD-108)

Chrysosporium species - Conidiophores may be 'ramified', forming tree-like structures. 
(400X, LPCB, DMD-108)

Chrysosporium species - conidia frequently stain more intensely than do the conidiophores which bear them or the hypha themselves.
(100X, LPCB, DMD-108)

Chrysosporium species - conidia may form short chains or develop as intercalary conidia (within the hyphae).  Here (arrow) appears to show such a short chain or possibly intercalary conidia.
(400X, LPCB, DMD-108)

 Chrysosporium species - another example of what appears to be a chain of conidia or alternatively might be described as intercalary (within the hypha) conidia.
(400+10X, LPCB, DMD-108)

Chrysosporium species - intercalary conidia are sometimes formed and may appear as a cylindrical or barrel shaped structure or may be seen as a bulge on only one side of the hyphae (arrows).
(1000X, LPCB, DMD-108)

 Chrysosporium species -typical appearance.
(400X, LPCB, DMD-108)

Chrysosporium species - as above.
(400X, LPCB, DMD-108)

Chrysosporium species - another example.
(400X, LPCB, DMD-108)

Chrysosporium species
(400X, LPCB, DMD-108)

 Chrysosporium species - sometimes it is difficult to tell whether there is a chain of conidia, a true intercalary conidium or whether there are just overlapping conidiophores which give the appearance of chaining.  (400+10X, LPCB, DMD-108)

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

 Chrysosporium species - conidia are rather thin walled (see center right of photo)
(1000X, LPCB, DMD-108)

 Chrysosporium species - oversaturation of the blue could not be effectively corrected with photo editing programs - then again, I just like this shot!
(1000X, LPCB, DMD-108)

Chrysosporium species - conidia are usually one-celled and about (2 – 9 X 3 – 13 µm).
(1000X, LPCB, DMD-108)

 Chrysosporium species - conidia are clavate (club shaped) and have a round apex (far end) and a broad, flat base where attached to the conidiophore.  Sources state that remnants of the attachment point (conidiophore) may remain attached to free conidia, however, I have not observed this in the photos I've taken.  The separation of the conidia from the conidiophore appears to be quite clean.
Here also you can see that the conidiophores are minimally differentiated from the hypha itself.  There is no uniquely recognizable,or elaborate structure to the conidiophores  Conidiophores appear to have variable lengths.   Condia appear to arise directly from the hyphae (sessile) and also may be on longer, simple or branched conidiophores.
(1000X, LPCB, DMD-108)

Chrysosporium species - rather delicate looking conidiophores - like fine pedicile-like strands attaching the conidia to the hyphae.  (1000X, LPCB, DMD-108)

Chrysosporium species - again, fine structured conidiophores attached to the tear-drop or clavate (club shaped) conidia.  (400X, LPCB, DMD-108)

Chrysosporium species - conidia on conidiophores arising from all sides of the hyphal element.
(1000X, LPCB, Nikon)

Chrysosporium species - Last photo.  Teardrop or clavate shaped conidia attached to septate hyphae via delicate, minimally differentiated conidiophores.
(1000X, LPCB, Nikon)

Chrysosporium is resistant to cycloheximide and therefore may be isolated on selective media used for primary isolation of dermatophytes.
Chrysosporium is urea positive.

Notes:  Chrysosporium species may develop branches diverging at 45ᵒ angles whereas the branches formed by dermatophytes are borne at angles closer to 90ᵒ.

Chrysosporium may produce conidia as short, terminal chains which are not seen in dermatophytes.
Young cultures of Chrysosporium may be confused with Blastomyces dermatitidis however they are not thermally dimorphic as is Blastomyces.

Chrysosporium may also be confused with Emmonsia parva, however Chrysosporium does not produce adiaconidia at 37ᵒC and some species fail to grow at 37ᵒC.

Chrysosporium can be distinguished from Sporotrichum species as the latter spreads rapidly to cover the entire media surface, fails to grow on cycloheximide, and usually forms abundant arthroconidia which may break from the hyphae to form clusters.

One source states that species which produce short terminal chains of conidia, grouped in small tree-like clusters,  are now considered to belong to the genus Geomyces rather than Chrysosporium.

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