Penicillium roqueforti
Penicillium roqueforti is a common saprotrophic fungus in the genus "Penicillium". Widespread in nature, it can be isolated from soil, decaying organic matter, and plants. The major industrial use of this fungus is the production of blue cheeses, flavouring agents, antifungals, polysaccharides, proteases, and other enzymes. The fungus has been a constituent of Roquefort, Stilton, Danish blue, Cabrales, Gorgonzola, and other blue cheeses. Other blue cheeses are made with "Penicillium glaucum". Classification. First described by American mycologist Charles Thom in 1906, "P. roqueforti" was initially a heterogeneous species of blue-green, sporulating fungi. They were grouped into different  species based on phenotypic differences, but later combined into one species by Kenneth B. Raper and Thom (1949). The "P. roqueforti" group got a reclassification in 1996 due to molecular analysis of ribosomal DNA sequences. Formerly divided into two varieties ― cheese-making ("P. roqueforti" var. "roqueforti") and patulin-making ("P. roqueforti" var. "carneum") ― "P. roqueforti" was reclassified into three species: "P. roqueforti", "P. carneum", and "P. paneum". The complete genome sequence of "P. roqueforti" was published in 2014. Description. As this fungus does not form visible fruiting bodies, descriptions are based on macromorphological characteristics of fungal colonies growing on various  standard agar media, and on microscopic characteristics. When grown on Czapek yeast autolysate agar or yeast-extract sucrose (YES) agar, "P. roqueforti" colonies are typically 40 mm in diameter, olive brown to dull green (dark green to black on the reverse side of the agar plate), with a velutinous texture. Grown on malt extract agar, colonies are 50 mm in diameter, dull green in color (beige to greyish green on the reverse side), with arachnoid (with many spider-web-like fibers) colony margins. Another characteristic morphological feature of this species is its production of asexual spores in phialides with a  distinctive brush-shaped configuration. Evidence for a sexual stage in "P. roqueforti" has been found, based in part on the presence of functional mating-type genes and most of the important genes known to be involved in meiosis. In 2014, researchers reported inducing the growth of sexual structures in "P. roqueforti", including ascogonia, cleistothecia, and ascospores. Genetic analysis and comparison of many different strains isolated from various environments around the world indicate that it is a genetically diverse species. "P. roqueforti" is known to be one of the most common spoilage molds of silage. It is also one of several  different moulds that can spoil bread. Uses. The chief industrial use of this species is the production of blue cheeses, such as its namesake Roquefort, Bleu de Bresse, Bleu du Vercors-Sassenage, Brebiblu, Cabrales, Cambozola (Blue Brie), Cashel Blue, Danish blue, Polish Rokpol made from cow's milk, Fourme d'Ambert, Fourme de Montbrison, Lanark Blue, Shropshire Blue, and Stilton, and some varieties of Bleu d'Auvergne and Gorgonzola. (Other blue cheeses, including Bleu de Gex and Rochebaron, use "Penicillium glaucum".) Strains of the microorganism are also used to produce compounds that can be employed as antibiotics, flavours, and fragrances, uses not  regulated under the U.S. Toxic Substances Control Act. Its texture is chitinous. Secondary metabolites. Considerable evidence indicates that most strains are capable of producing harmful secondary metabolites (alkaloids and other mycotoxins) under certain growth conditions. Aristolochene is a sesquiterpenoid compound produced by "P. roqueforti", and is likely a precursor to the toxin known as PR toxin, made in large amounts by the fungus. PR-toxin has been implicated in incidents of mycotoxicoses resulting from eating contaminated grains. However, PR toxin is not stable in cheese and breaks down to the less toxic PR imine. Secondary metabolites of "P. roqueforti", named  andrastins A-D, are found in blue cheese. The andrastins inhibit proteins involved in the efflux of anticancer drugs from multidrug-resistant cancer cells. "P. roqueforti" also produces the neurotoxin roquefortine C. However, the levels of roquefortine c in cheese made from it is usually too low to produce toxic effects. The organism can also be used for the production of proteases and specialty chemicals, such as methyl ketones, including 2-heptanone.