Discovery of a sexual cycle in the opportunistic fungal pathogen Aspergillus fumigatus.

Aspergillus fumigatus is a saprotrophic fungus whose spores are ubiquitous in the atmosphere. It is also an opportunistic human pathogen in immunocompromised individuals, causing potentially lethal invasive infections, and is associated with severe asthma and sinusitis. The species is only known to reproduce by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies, genome analysis, the presence of mating-type genes and expression of sex-related genes in the fungus. Here we show that A. fumigatus possesses a fully functional sexual reproductive cycle that leads to the production of cleistothecia and ascospores, and the teleomorph Neosartorya fumigata is described. The species has a heterothallic breeding system; isolates of complementary mating types are required for sex to occur. We demonstrate increased genotypic variation resulting from recombination between mating type and DNA fingerprint markers in ascospore progeny from an Irish environmental subpopulation. The ability of A. fumigatus to engage in sexual reproduction is highly significant in understanding the biology and evolution of the species. The presence of a sexual cycle provides an invaluable tool for classical genetic analyses and will facilitate research into the genetic basis of pathogenicity and fungicide resistance in A. fumigatus, with the aim of improving methods for the control of aspergillosis. These results also yield insights into the potential for sexual reproduction in other supposedly 'asexual' fungi.

Morphological and molecular characterisation of Penicillium roqueforti and P. paneum isolated from baled grass silage.

The morphological and molecular features of Penicillium roqueforti and P. paneum isolated from baled grass silage were characterised. A total of 315 isolates were investigated, comprising 237 P. roqueforti and 78 P. paneum isolates randomly selected from more than 900 Penicillium colonies cultured from bales. The macromorphological features of both species broadly agreed with the literature, but the micromorphological features differed in some respects. When observed using SEM, P. roqueforti and P. paneum had finely roughened conidia, and conidiophores, phialides and conidia of P. paneum were each larger than those of P. roqueforti. Based on the phylogenetic analysis of partial sequences of beta-tubulin and acetyl co-enzyme A (CoA) synthetase genes, P. roqueforti and P. paneum isolates were found to be monophyletic species.

Mycotoxins and other secondary metabolites produced in vitro by Penicillium paneum Frisvad and Penicillium roqueforti Thom isolated from baled grass silage in Ireland.

Secondary metabolites produced by Penicillium paneum and Penicillium roqueforti from baled grass silage were analyzed. A total of 157 isolates were investigated, comprising 78 P. paneum and 79 P. roqueforti isolates randomly selected from more than 900 colonies cultured from bales. The findings mostly agreed with the literature, although some metabolites were not consistently produced by either fungus. Roquefortine C, marcfortine A, and andrastin A were consistently produced, whereas PR toxin and patulin were not. Five silage samples were screened for fungal metabolites, with two visually moldy samples containing up to 20 mg/kg of roquefortine C, mycophenolic acid, and andrastin A along with minor quantities (0.1-5 mg/kg) of roquefortines A, B, and D, festuclavine, marcfortine A, and agroclavine. Three visually nonmoldy samples contained low amounts of mycophenolic acid and andrastin A. The ability of both molds to produce a diverse range of secondary metabolites in vitro and in silage should be a concern to livestock producers.

Fungi isolated from contaminated baled grass silage on farms in the Irish Midlands.

The incidence of fungal growth on baled grass silage was recorded on 35 farms in the Irish Midlands in 2003. Fungal colonies were visible on 58 of 64 bales examined and the number of colonies per bale ranged from 1 to 12. On average, 5% of bale surface areas were affected. The fungus most prevalent on bales was Penicillium roqueforti, present on 86% of bales and representing 52% of all isolates. Other moulds isolated were Penicillium paneum, Geotrichum, Fusarium and mucoraceous species. Schizophyllum commune was observed protruding through the plastic film on bales on 17 of the 35 farms.