Penicillium roqueforti var. viride Datt.-Rubbo (1938)[3]
Penicillium roqueforti var. punctatum S.Abe (1956)
Penicillium conservandi Novobr. (1974)
Penicillium roqueforti is a common
saprotrophicfungus in the
genusPenicillium. Widespread in nature, it can be isolated from soil, decaying organic matter, and plants.
First
described by American mycologist
Charles Thom in 1906,[5]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.[6] The complete
genome sequence of P. roqueforti was published in 2014.[7]
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.[8] Another characteristic morphological feature of this species is its production of asexual spores in
phialides with a distinctive brush-shaped configuration.[9][10][11]
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.[12] 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.[13]
P. roqueforti can tolerate cold temperatures, low oxygen levels, and both alkali and weaker acid preservatives which allows the fungi to thrive and be found in dairy environments, such as cheese. On the other hand, it also spoils refrigerated foods and meats, breads, and silage.
When placed into cream and aerated, P. roqueforti produces concentrated blue cheese flavoring, a type of
enzyme-modified cheese.[15] A similar flavoring can be produced using other sources of fatty acids such as coconut oil.[16]
Strains of the microorganism are also used to produce compounds that can be employed as
antibiotics, flavours, and fragrances,[17] 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.[18][19][20][21]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.[22]PR-toxin has been implicated in incidents of
mycotoxicoses resulting from eating contaminated grains.[20][23] However, PR toxin is not stable in cheese and breaks down to the less toxic PR
imine.[24]
P. roqueforti also produces the
neurotoxinroquefortine C.[26][27]
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
methylketones, including
2-heptanone.[28]
^Westling R. (1911). "Über die grünen Spezies der Gattung Penicillium". Arkiv før Botanik (in German) (1): 71.
^Biourge P. (1923). "Les moissisures du groupe Penicillium Link". La Cellule (in French). 33: 7–331 (see pp. 203–4).
^Dattilo-Rubbo S. (1938). "The taxonomy of fungi of blue-veined cheese". Transactions of the British Mycological Society. 22 (1–2): 174–81.
doi:
10.1016/s0007-1536(38)80015-2.
^Raper KB (1957). "Nomenclature in Aspergillus and Penicillium". Mycologia. 49 (5): 644–662.
doi:
10.2307/3755984.
JSTOR3755984.
^Samson RA, Gams W (1984). "The taxonomic situation in the hyphomycete genera Penicillium, Aspergillus and Fusarium". Antonie van Leeuwenhoek. 50 (5–6): 815–24.
doi:
10.1007/BF02386244.
PMID6397143.
S2CID7084024.