Aspergillus species
A. fumigatus Fres. (Sartorya fumigata)
Culture and morphological characteristics.
Identification
of A. fumigatus is based predominantly upon the morphology of the
conidia and conidiophores. The organism is characterized by green echinulate
conidia, 2.5 to 3 micrometer in diameter, produced in chains basipetally
from greenish phialides. 6 to 8 by 2 to 3 micrometer in size. A few isolates
of A. fumigatus are pigmentless and produce white conidia (1).
The chains of conidia are borne directly on broadly clavate vesicles (20
to 30 micrometer in diameter) in the absence of metulae (Fig. 1). No sexual
stage is known for this species. A. fumigatus is a fast grower:
the colony size can reach 4 ± 1 cm within a week when grown on Czapek-Dox
agar at 25°C (2). A. fumigatus is a thermophilic species,
with -growth occurring at temperatures as high as 55°C and
survival maintained at temperatures up to 70°C (3, 4, 5, 6).
A. fumigatus is morphologically more variable (6, 7, 8) than was originally described by Raper and Fennell (2). These variations have led to the description of several varieties of A. fumigatus, including acolumnaris, phialiseptus, ellipticus, and sclerotiorum, with the distinctions being based on only slight morphological differences. A. fumigatus, A. brevipes, A.. duricaulis, A.. unilateralis, A.. viridinutans. together with anamorphs of species within the perfect genus Neosartorya, a genus in which morphologically related species have been grouped, are classified as Aspergillus sect. fumigati.
The search for a sexual state of A. fumigatus has been successfully achieved (9) leading to the renaming of A. fumigatus as Sartorya fumigata.
References
1 - Sarfati, J., Daiquin, M., Debeaupuis, J.P., Paris, S. & Latge, J-P. Unpublished data.
2 - Raper, K.B. & Fennel, D.I. (1965). Aspergillus fumigatus group. p. 238-268. In K.B.Raper and D.I.Fennel (ed.), the genus Aspergillus. The William & Wilkins Co., Baltimore, Md.
3 - Haines, J. (1995). Aspergillus in compost: straw man or fatal flaw. Biocycle 6: 32-35.
4 - Kwon-Chung, K.J. & Bennett, J.E. (1992). Medical mycology. Lea & Febiger. Philadelphia, Pa.
5 - Samson, R.A. & Van Reenen-Hoekstra, E.S. (1988) Introduction to food-borne fungi. Centraalbureau voor Schimmelcultures, Baarn, Delft, The Netherlands.
6 - Leslie, C.E., Flannigan, B. & Milne, L.J.R. (1988). Morphological studies on clinical isolates of Aspergillus fumigatus. J. Med. Vet. Mycol, 26: 335-341.
7 - Samson, R.A. (1994). Current systematics of the genus Aspergillus, p. 261-276. In K.A.Powell, A. Renwick & J.F.Peberdy (ed.), The genus Aspergillus: from taxonomy and genetics to industrial application. Plenum Press, London, United Kingdom.
8 - Schmidt, A. & Wolff, M.H. (1997). Morphological characteristics of Aspergillus fumigatus strains isolaed from patients samples. Mycoses 40: 347-351.
9 - Céline M. O'Gorman, Hubert T. Fuller & Paul S. Dyer (2008). Discovery of a sexual cycle in the opportunistic fungal pathogen Aspergillus fumigatus. Nature advance online publication 30 November 2008 (doi:10.1038/nature07528).