A taxonomic and ecological overview of cheese fungi

Cheese is made from milk by a succession of microbes (bacteria, yeasts and fungi) that determine the consistency and flavor of the cheese. Apart from the emblematic species, Penicillium camemberti and Penicillium roqueforti, cheese fungi are not well known. Here we present a taxonomic and phylogenetic overview of the most important filamentous cheese Ascomycota based on 133 isolates provided by the producers of cheese and cheese starter cultures and 97 isolates from culture collections. We checked the congruence of different gene genealogies to circumscribe cheese species and our results allow us to propose molecular targets for their identification. To study their phylogenetic affiliation, we used LSU rDNA and showed that cheese fungi are found in two classes, the Eurotiomycetes with Penicillium species (Eurotiales) and Sporendonema casei/Sphaerosporium equinum (Onygenales), and the Sordariomycetes with Scopulariopsis species (Microascales) and Fusarium domesticum (Hypocreales). Some of these fungi, such as, P. camemberti, F. domesticum, Scopulariopsis flava and S. casei, are only known from cheeses and are probably adapted to this particular habitat, which is extremely rich in protein and fat. Other cheese fungi are ubiquitous, such as, P. roqueforti, Scopulariopsis candida and Scopulariopsis fusca.