Factors affecting germination of ascospores in Aspergillus fumigatus


  • Sameira S. Swilaiman Department of Basic Sciences, College of Dentistry, Hawler Medical University, Erbil, Iraq




Ascosopre germination, A. fumigates, Factors


Background and objective: Aspergillus fumigatus is the most common airborne fungal pathogen of humans. It is an opportunistic human pathogen in immunocompromised hosts. Following the recent discovery of the sexual reproductive cycle ascospores of this fungus were available and their germination was studied in the present study. This study aimed to study factors influencing germination of ascospores of A. fumigatus.

Methods: A total of 12 environmental A. fumigatus were chosen in both mating type, examined for sexual reproduction by crossing complementary mating type, following removing of cleistothecia, preparation of ascospore suspensions in 0.05% Tween 20, then heat treated to kill any remaining conidia.

Results: Ascospore germination of greater than 75% occurred at 28 °C on a wide variety of mycological media, 0.5% (ACM) was chosen for use in subsequent studies. Ascospores did not require a heat treatment prior to germination; however, heat treatment of ascospores at 75 °C for 1 hour previous to incubation enhanced germination to 89% and also served to inactivate contaminating conidia. Ascospores also exhibited a psychrotolerance following exposure at -80 °C for 96 hours. Inoculum concentration did not have a significant effect on germination rates between the range of 0.125×106 to 4×106 ascospores ml-1 (P >0.05).   

Conclusion: This study demonstrated that ascospore germination of greater than 75% occurred at 28 °C on a wide variety of mycological media. Ascospores of A. fumigatus are thermotolerant also exhibited a psychrotolerance whilst at the same time retaining viable sexual ascospores, to assess percentage germination a drop of Lactophenol Cotton Blue was added.


Metrics Loading ...


Latgé JP.Aspergillus fumigatus and Aspergillosis. Clin Microbiol Rev 1999; 12:310–50.

Denning DW. Invasive Aspergillosis. Clin Infect Dis 1998; 26:781–803.

O’Gorman CM, Fuller HT, Dyer PS. Discovery of a sexual cycle in the opportunistic fungal pathogen Aspergillus fumigatus. Nature 2009; 457:471–4.

Barton NH, Charlesworth B. Why sex and recombination? Science 1998; 281:1986–90.

Mouchacca J. Heat tolerant fungi and applied research: Addition to the previously treated group of strictly thermotolerant species. World J Microbiol Biotechnol 2007; 23:1755–70.

Dijksterhuis J, Nijsse J, Hoekstra FA, Golovina EA. High viscosity and anisotropy characterise the cytoplasm of fungal dormant stress-resistant spores. Eukaryot Cell 2007; 6:157–70.

Coluccio AE, Rodriguez RK, Kernan MJ, Neiman AM. The yeast spore wall enables spores to survive passage through the digestive tract of Drosophila. Plos One 2008; 3: e2873.

McEvoy IJ, Stuart MR. Temperature tolerance of Aspergillus fischeri var. glaber in canned strawberries. Ir J Agric Res 1970; 9:59–67.

Beuchat L. Extraordinary heat resistance of Talaromyces flavus and Neosartorya fischeri ascospores in fruit products. J Food Sci 1986; 51: 1506_10.

Dijksterhuis J, Teunissen P. Dormant ascospores of Talaromyces macrosporus are activated to germinate after treatment with ultra high pressure. J Appl Microbiol 2003; 96:162–9.

Leach CM. Regulation of perithecium development and maturation in Pleospora herbarum by light and tempreture. Trans Br mycol Soc 1971; 57:295–315.

Splittstoesser D, Lammers J, Downing D, Churey J. Heat resistance of Eurotium herbariorum, a xerophilic mold. J Food Sci 1989; 54:683_5.

Araujo R, Rodrigues AG. Variability of germinative potential among pathogenic species of Aspergillus. J. Clin. Microbiol 2004; 42:4335–7.

Swilaiman SS. Sexual Potential and Population Biology of Fungal Aspergillus and Penicillium species, PhD thesis. University of Nottingham; 2013.

Rhodes JC. Aspergillus fumigatus: Growth and virulence. Med Myco 2006; 44:S77–81.

Dijksterhuis J, Teunissen PG. Dormant ascospores of Talaromyces macrosporus are activated to germinate after treatment with ultra high pressure. J Appl Microbiol 2004; 96:162–9.

Dijksterhuis J, van Driel KG, Sanders MG, Molenaar D, Houbraken JA, Samson RA, et al. Trehalose degradation and glucose efflux precede cell ejection during germination of heat-resistant ascospores of Talaromyces macrospores. Arch Microbiol 2002; 178:1–7.

Gomez-Lopez A, Aberkane A, Petrikkou E, Mellado E, Rodriguez-Tudela J, Cuenca-Estrella M. Analysis of the Influence of Tween Concentration, Inoculum Size, Assay Medium, and Reading Time on Susceptibility Testing of Aspergillus spp. J clinic Microbiol 2005; 43:1251–5.

Gupta A, Gautam N, Modi D. Optimization of a-amylase production from free and immobilized cells of Aspergillus nige. E3 J Biotechnol Pharmacol Res 2010; 1:001–8.

Deacon JW. Fungal Biology. 4th ed. Oxford, UK: Blackwell Publishing; 2006.

Manavathu EK, Cutright J, Chandrasekar PH. Comparative study of susceptibilities of germinated and ungerminated conidia of Aspergillus fumigatus to various antifungal agents. J Clin Microbiol 1999; 37:858–61.




How to Cite

Swilaiman, S. S. (2018). Factors affecting germination of ascospores in Aspergillus fumigatus. Zanco Journal of Medical Sciences (Zanco J Med Sci), 22(2), 198–207. https://doi.org/10.15218/zjms.2018.027



Original Articles