Hubert T. Fuller

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.

Pan-European Distribution of White-Nose Syndrome Fungus (Geomyces destructans) Not Associated with Mass Mortality

Background The dramatic mass mortalities amongst hibernating bats in Northeastern America caused by “white nose-syndrome” (WNS) continue to threaten populations of different bat species. The cold-loving fungus, Geomyces destructans, is the most likely causative agent leading to extensive destruction of the skin, particularly the wing membranes. Recent investigations in Europe confirmed the presence of the fungus G. destructans without associated mass mortality in hibernating bats in six countries but its distribution remains poorly known. Methodology/Principal Findings We collected data on the presence of bats with white fungal growth in 12 countries in Europe between 2003 and 2010 and conducted morphological and genetic analysis to confirm the identity of the fungus as Geomyces destructans. Our results demonstrate the presence of the fungus in eight countries spanning over 2000 km from West to East and provide compelling photographic evidence for its presence in another four countries including Romania, and Turkey. Furthermore, matching prevalence data of a hibernaculum monitored over two consecutive years with data from across Europe show that the temporal occurrence of the fungus, which first becomes visible around February, peaks in March but can still be seen in some torpid bats in May or June, is strikingly similar throughout Europe. Finally, we isolated and cultured G. destructans from a cave wall adjacent to a bat with fungal growth. Conclusions/Significance G. destructans is widely found over large areas of the European continent without associated mass mortalities in bats, suggesting that the fungus is native to Europe. The characterisation of the temporal variation in G. destructans growth on bats provides reference data for studying the spatio-temporal dynamic of the fungus. Finally, the presence of G. destructans spores on cave walls suggests that hibernacula could act as passive vectors and/or reservoirs for G. destructans and therefore, might play an important role in the transmission process.

White-Nose Syndrome Fungus (Geomyces destructans) in Bat, France

White-nose syndrome is caused by the fungus Geomyces destructans and is responsible for the deaths of >1,000,000 bats since 2006. This disease and fungus had been restricted to the northeastern United States. We detected this fungus in a bat in France and assessed the implications of this finding.

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.

Effect of sample preservation methods on the viability of Geomyces destructans, the fungus associated with white-nose syndrome in bats

Geomyces destructans is a fungus directly associated with white-nose syndrome (WNS), a recently discovered disease that has caused the death of over one million bats in North America and therefore has prompted intense scientific investigation into its biology. If precautions are not taken, the spread of G. destructans by human transportation for scientific study may be a substantial threat to bat populations. We investigated the viability of G. destructans after being exposed to commonly used DNA/RNA preservation methods. Our first experiment revealed that G. destructans is able to germinate after an eight day storage period in RNAlater or kept dry but could not germinate after storage in 70% or absolute ethanol for the same time period. Storing G. destructans samples at different temperatures did not substantially affect the results. In a second experiment, we showed that G. destructans conidia were only killed after being stored in 70% ethanol for a minimum of 24 hours while only 30 minutes were necessary when stored in absolute ethanol. Our results suggest that the DNA/RNA preservation method has an important impact on the ability of G. destructans to remain viable and should therefore be considered before samples are transported, especially to regions where the fungus has not yet been documented. Our results also strongly advocate the use of high concentrations (i.e., absolute) ethanol over 70% ethanol to rapidly kill G. destructans.

Schizophyllum commune on big-bale grass silage in Ireland

Grass silage is a key source of forage for over-wintering livestock in Ireland. In the early 1990s Schizophyllum commune emerged as a contaminant of big-bale silage. A fungus rarely observed in Irish woodlands, S. commune is now commonly found on baled silage throughout Ireland and is also recorded on silage in Britain. Characteristics of the fungus on bales are described and potential consequences of its occurrence on silage are discussed.