Eurotiales reproduce sexually in different ways. In general, a compatible mating type is needed for sexual reproduction. Homothallic species are self-fertile and both mating types are present within their genome. Therefore, each individual colony can produce sexual spores, while it can also recombine with another strain. Heterothallic species, on the other hand, only contain one mating type in their genomes, meaning that they need to encounter another colony with the compatible mating type locus in order to reproduce sexually. During sexual reproduction, fruiting bodies like cleistothecia are formed, in which asci are produced that contain the sexually formed spores called ascospores.Many heterothallic Eurotiales were assumed to be asexual because their sexual form of reproduction was never observed. For this reason, they were called anamorphic fungi,
Aspergillus niger and Penicillium roquefortiThe fungus A. niger is well known for its biotechnological applications and used for citric acid and enzyme production. Because of its industrial role, it has been widely used as a model organism to study fungal genetics (Pel et al., 2007). In addition, it is a food spoilage fungus causing black rot in grapes, onions and other fruits and vegetables. The fungus grows well under acidic conditions and therefore, it is a common spoiler of yoghurt products (Gougouli and Koutsoumanis, 2017).The fungus P. roqueforti, is known as the fermentation organism of blue vain cheeses (Coton et al., 2020;Ropars et al., 2012). It is well adapted to grow at low temperatures (Nguyen Van Long et al., 2021) and is able to grow at high concentrations of weak acids (Samson et al., 2019). Therefore, it is also an efficient spoiler of dairy products with a chilled chain storage. In addition, it is a common spoiler of bakery products and silage (Samson et al., 2019).Like P. variotii, both species are heterothallic and require mating with another strain with compatible mating type for sexual reproduction. Strains of P. roqueforti can recombine under specific conditions (Ropars et al., 2014), while sexual reproduction of A. niger has not yet been observed. Nevertheless, there are conditions in which sexual structures called sclerotia are formed (Ellena et al., 2021) and some strains can be recombined under lab conditions using the parasexual cycle (Arentshorst and Ram, 2018).
STRESS RESISTANCE IN EUROTIALESThe ability of a fungus to spoil food is largely determined by its stress resistance and, as a consequence, its ability to grow through hurdles applied within the food environments. Stress resistance of fungal spores, which are regarded dormant with minimal metabolic activity (Novodvorska et al., 2016;Teertstra et al., 2017) and growing vegetative mycelium is different. In general, spores are considered more stress resistant than vegetative cells (Wyatt et al., 2013), but the resistance of mycelium to food preservative factors is equally important as it has to deal with low water activity and the presence of preservatives in order to grow.Spores mus...