Sexual Reproduction as the Cause of Heat Resistance in the Food Spoilage Fungus Byssochlamys spectabilis (Anamorph Paecilomyces variotii )

Abstract

Paecilomyces variotii is a common cosmopolitan species that is able to spoil various food-and feedstuffs and is frequently encountered in heat-treated products. However, isolates from heat-treated products rarely form ascospores. In this study we examined by using molecular techniques and mating tests whether this species can undergo a sexual cycle and form ascospores. The population structure of this species was examined by analyzing the nuclear ribosomal internal transcribed spacer 1 (ITS1) and ITS2 and the 5.8S rRNA gene, as well as partial ␤-tubulin, actin, and calmodulin gene sequences. Phylogenetic analyses revealed that P. variotii is a highly variable species. Partition homogeneity tests revealed that P. variotii has a recombining population structure. In addition to sequence analyses, mating experiments indicated that P. variotii is able to form ascomata and ascospores in culture in a heterothallic manner. The distribution of MAT1-1 and MAT1-2 genes showed a 1:1 ratio in the progeny of the mating experiments. From the sequence analyses and mating data we conclude that P. variotii is the anamorph of Talaromyces spectabilis and that it has a biallelic heterothallic mating system. Since Paecilomyces sensu stricto anamorphs group within Byssochlamys, a new combination Byssochlamys spectabilis is proposed. (2) is a common cosmopolitan mold found in soils, indoor environments, plants, animals, and foodstuffs (33,39,40,42). It is a fast-growing thermotolerant fungus that is able to grow at low oxygen levels and in the presence of preservatives, able to form the mycotoxin viriditoxin, and able to survive heat treatments (19,33). The combination of the previously mentioned features makes this species an important organism and one of the most frequently encountered spoilage fungi in various foodstuffs. This species is one of the most heat-resistant fungi known, and its presence in pasteurized beverages causes great economic losses (52). Although P. variotii produces thick-walled hyphae and chlamydospores, ascospores, which are usually considered to be the heat-resistant propagule in other fungi, are rarely found in culture. As a result, the route of P. variotii contamination remains mostly unknown (19). Besides spoiling food, it is also associated with many types of human infections. Endocarditis is the most common infection produced by this species and has a very bad prognosis (5). Industrial applications have also been proposed with P. variotii isolates; examples include tannase production (3, 28) and biofiltration of toluene (7, 10). Paecilomyces variotii BainierAscomycetes with anamorphs in the genera Penicillium, Aspergillus, and Paecilomyces have been classified in the Trichocomaceae family (2, 29, 30, 34). The connection of Paecilomyces anamorphs with the ascomycete Byssochlamys was first proposed by Stolk and Samson (44). A recent molecular study revealed that P. variotii forms a well-defined clade within the Trichocomaceae, together with other thermophilic Paecilomyces species and Byssochlamys teleomorph...

Identification ofPaecilomyces variotiiin Clinical Samples and Settings

“…P. lilanicus, T. eburneus, and H. avellanea had different susceptibility profiles; and flucytosine and voriconazole were the least active of the antifungal drugs tested against these species. Our results indicate that correct species identification is important to help guide appropriate antifungal therapy.Paecilomyces variotii is a commonly occurring species that has previously been isolated from various substrates, including (pasteurized) foods, soil, indoor air, and wood (23,36,41,42,43). However, it is also associated with many types of human infections and is listed among the emerging causative agents of opportunistic mycoses in immunocompromised hosts.…”

“…Paecilomyces variotii is a commonly occurring species that has previously been isolated from various substrates, including (pasteurized) foods, soil, indoor air, and wood (23,36,41,42,43). However, it is also associated with many types of human infections and is listed among the emerging causative agents of opportunistic mycoses in immunocompromised hosts.…”

The Chemical Diversity of the Ascomycete Fungus Paecilomyces variotii

“…As a contaminant mould, this fungus can also spoil a wide range of food and feedstuff. It is frequently encountered in heat-treated industrial products, since it can withstand brief exposure of temperatures at 80-100°C for up to 15 min [2,10,11].…”

Advances in consolidated bioprocessing systems for bioethanol and butanol production from biomass: a comprehensive review

“…variotii is an ascomycete fungus commonly found in composts, soils and food products. This fungus is also known from decaying wood and creosotetreated wood utility poles (Houbraken et al, 2008(Houbraken et al, , 2010. Zerva et al (2014) evaluated this fungus for the first time as a candidate CBP species for the production of bioethanol from lignocellulose.…”