Revealing relationships in Trichocomaceae, with emphasis on Penicil

Abstract

The majority of Trichocomaceae are saprobes and have diverse physiological properties. They are capable of growing under extreme conditions, such as extremely low water activities, low temperatures (psychrotolerant), high temperatures (thermotolerant), low acidity levels and/or low oxygen levels. Some are known to have a positive or negative impact on human activities. They are associated with food spoilage and mycotoxin production and can occur in the indoor environment, causing health hazards by the formation of β-glucans, mycotoxins and surface proteins. Some species are opportunistic pathogens, while others are exploited in biotechnology for the production of enzymes, antibiotics and other products. This thesis provides insight into the phylogeny of Trichocomaceae, taxonomy of Penicillium with emphasis on sections Citrina and Lanata-divaricata and mating behaviour of Paecilomyces variotii in relation to species delimitation and food spoilage. The phylogeny of Penicillium and its relationship with other members of Trichocomaceae was studied, and an updated list of accepted Penicillium names is provided. Using a multigene approach and phenotypic characters, the Trichocomaceae are divided in three separate families: Aspergillaceae, Thermoascaceae and Trichocomaceae. Phylogenetic analysis shows that Penicillium is polyphyletic and members of the subgenera Aspergilloides, Furcatum and Penicillium belong to Penicillium s. str., while the majority of species of subgenus Biverticillium belong to the redefined genus Talaromyces. Thermophilic Penicillium-like fungi (e.g. Talaromyces emersonii) have gained much attention in biotechnology the last decades, primarily because of their capacity to produce thermostable enzymes. These species are unrelated to Penicillium sensu stricto and a new genus named Rasamsonia was proposed for these fungi. Species belonging to Penicillium sections Citrina and Lanata-divaricata have a worldwide distribution and commonly occur in soils. New insights in the phylogeny and taxonomy of these sections show that section Citrina and Lanata-divaricata includes 39 species and 33 species, respectively, 22 of those are described here as new. These species have unique properties and the newly proposed classification scheme may help in determining more accurate the mycobiota of soils, which may be important for biodiversity, ecological and climate change studies. Furthermore, some of these species are associated with leaf litter decomposition and may be efficient lignocellulose degraders and could represent a new source for cellulolytic and xylanolytic enzymes, while others are producers of uncharacterized compounds that might represent novel drug leads (incl. novel antibiotics). Paecilomyces variotii, a species related to Penicillium, is a common cosmopolitan species that is able to spoil various food- and feedstuffs and is frequently encountered in heat-treated products. Ascospores, which are usually considered to be the heat-resistant propagule in other fungi, were rarely found in P. variotii cultures. As a result, the route of P. variotii contamination remained largely unknown. The mating type genes MAT1-1 and MAT1-2 were determined and these appeared to be evenly distributed among strains isolated from heat treated products, showing the presence of cryptic sexuality. Mating experiments indicated that P. variotii is able to form ascomata and ascospores in culture in a heterothallic manner, giving insight in the contamination route of this heat resistant fungus.