Abstract
A sexual cycle in Aspergillus fumigatus was first described in 2009 with isolates from Dublin, Ireland. However, the extent to which worldwide isolates can undergo sexual reproduction has remained unclear. In this study a global collection of 131 isolates was established with a near 1:1 ratio of mating types. All isolates were crossed to MAT1-1 or MAT1-2 Irish strains, and a subset of isolates from different continents were crossed together. Ninety seven percent of isolates were found to produce cleistothecia with at least one mating partner, showing that sexual fertility is not limited to the Irish population but is a characteristic of global A. fumigatus. However, large variation was seen in numbers of cleistothecia produced per cross, suggesting differences in the possibility for genetic exchange between strains in nature. The majority of crosses produced ascospores with >50% germination rates, but with wide variation evident. A high temperature heat shock was required to induce ascospore germination. Finally, a new set of highly fertile MAT1-1 and MAT1-2 supermater strains were identified and pyrimidine auxotrophs generated for community use. Results provide insights into the potential for the A. fumigatus sexual cycle to generate genetic variation and allow gene flow of medically important traits.
Highlights
Aspergillus fumigatus is a cosmopolitan saprotrophic fungus which plays an important role in the decomposition of organic matter and recycling of carbon and nitrogen, with soil and rotting vegetation being natural ecological niches [1,2]
A. fumigatus-like colonies were further purified by streaking on malt extract agar (MEA) or potato dextrose agar (PDA) plates supplemented with 0.05–0.1% Triton X100 at 37 ◦ C
A total of 131 isolates of A. fumigatus were obtained from six continents, of which 111 were from an environmental source and 20 from clinical specimens (Supplemental Table S1)
Summary
Aspergillus fumigatus is a cosmopolitan saprotrophic fungus which plays an important role in the decomposition of organic matter and recycling of carbon and nitrogen, with soil and rotting vegetation being natural ecological niches [1,2]. It is one of the most common microorganisms found in compost and is commonly found in human habitats, e.g., pillows [3,4]. These can be divided into major forms according to the site of infection and degree of colonisation, and include
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