Sunday 28 July 2013

Aspergillus versicolor

Aspergillus versicolor (mould, fungus)


Widespread distribution with ability to grow in temperate and colder regions which may restrict the growth of many other Aspergillus species.    Commonly found in soils and may be isolated from many foods, especially spices, dried cereals and nuts.  Frequently found in buildings with humidity & ventilation problems.


Has been implicated as the causative agent of a variety of human mycoses including onychomycosis, pulmonary disease and disseminated infection.  Association with disease is poorly documented which leaves doubt to its significance.

Macroscopic Morphology:
  • A.veriscolor has a slow to moderate rate of growth, maturing in about 3 to 7 days.

  • Expansion of colony is rather slow.

  • Growth is restricted at 35ºC.

  • Colony texture is suede-like, often with radial grooves.

  • Colonies can develop a variety of colours (hence the name – “versicolored”).

  • Colour ranges from pale green, greenish-beige, grey green, pinkish-green, salmon-green to dark green with shades of mauve or turquoise. (colour development is media dependant)
  • Exudate when present may be pint to reddish-brown.

  • Reverse is uncoloured to a reddish-brown or reddish-purple.

Aspergillus versicolor SAB 14 days 30ºC

Aspergillus verisicolor ~12 days - This photo taken from a previous isolate better shows the variability of the color produced by A.versicolor.  This species is capable of producing a variety of colors, hence the name - verisi-colored.

Microscopic Morphology:

Smooth conidiophores (~ 200 – 500 µm X 4 -7 µm) extend from septate hyphae.

Conidial heads support vesicles (9-16 µm dia) which are biseriate with metulae about the same size, or slightly shorter than the phialides.

The conidiogenous cells (metulae & phialides) loosely cover half to the entire vesicle.

Diminutive conidial heads can form which can resemble penicilli (Mimics Penicillium species structure).

Conidia (2-0 – 3.5 µm dia) are globose (round) and the walls usually have a slightly roughened appearance.

Globose hülle cells on occasion are present in some isolates.

 A.verisicolor -Edge of a slide culture at 48 hours of incubation.
 (LPCB, 250X, DMD-108)

A.verisicolor - fruiting structures
(LPCB, 400X, DMD-108) 


A.verisicolor -conidiophore -Stipe with vesicle at apex which is covered with metulae & phialides (Biseriate) that produce the conidia.  (LPCB, 400X, DMD-108)

A.veriscolor - just a closer look at the photo above adding 10X digital magnification to the optical.
(LPCB, 400+10X, DMD-108)

A.versicolor -I like photographs.  Another photo of the fruiting structure of A.versicolor.  Note the 'reduced' structures at the left of the photo.  More on those to come.
(LPCB, 400X, DMD-108)

A.verisicolor - yet another view
(LPCB, 400X, DMD-108)

A.versicolor -Biseriate structure (metulae & phialides) but difficult to tell in this photo.  Abundant conida seen chaining from the phialides.
(LPCB, 1000X, DMD-108)

A.versicolor -again difficult to see the biseriate structure at this resolution.  Image structures and colours seem to "bleed" together with the DMD-108 digital microscope.  Reducing saturation of the image did not help.
(LPCB, 1000+10X, DMD-108)

A.versicolor - Biseriate structure, although not tremendously clear, can be visualized in places in this photo. (LPCB, 1000+10X, DMD-108)

A.versicolor - somewhat of a messy photo, lacking clear structures, but I like it, so it is here!
(LPCB, 1000+10X, DMD-108)

A.versicolor - one characteristic of A.versicolor which aids in its identification is that it produced both fruiting structures typical of Aspergillus genus, the vesicle covered with conidiogenous cells (A), but also a reduced structure which can resemble penicilli  (B). (ie. somewhat looks like a Penicillium fungus.)  (LPCB, 400X, DMD-108)

A.versicolor - another photo where both structures (as described above) are seen in the same field.
(LPCB, 400X, DMD-108)

A.verisicolor - as above but clearer view of the reduced structure seen in the inset.
(LPCB, 400X, DMD-108)

A.versicolor - reduced penicilli structure.
(LPCB, 400X, DMD-108)

A.versicolor - another view of the reduced penicilli structure.  The variable color and the presence of these reduced structures are distinctive features of A.versicolor, thereby aiding in identification.
(LPCB, 400X, DMD-108)

A.versicolor - reduced penicilli structure.  No vesicle is present.
(LPCB, 1000+10X, DMD-108)

A.versicolor - this photo is taken at the edge of a slide culture after 48 hours incubation.  Numerous reduced forms appear to be present.  Background of photo is due to agar from the slide culture preparation remaining attached to the coverslip.
(LPCB, 400X, DMD-108)

A.versicolor - Conidia (2-0 – 3.5 µm dia) are globose (round) and the walls usually have a slightly roughened appearance.
(LPCB, 1000+10X, DMD-108)


Caution – A.versicolor’s fruiting structure may at first observation be confused with A.sydowii .   Colonial appearance differs substantially where A.sydowii has a distinctive blue-green colour in comparison to A.versicolor’s variable but dominant light-green shades.

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