Penicillium Genus

**Penicillium** is a genus of ~350 species of ascomycete mould, best known as the source of penicillin. The name derives from Latin *penicillus* ('little brush'), describing the brush-like arrangement of conidiophores that carry the spores — the same root as the English word 'pencil.' ## Key species - **Penicillium chrysogenum** (previously *P. notatum* in Fleming's day, later reclassified as *P. rubens*): the industrial penicillin producer. Modern industrial penicillin traces back to a single strain, NRRL 1951, isolated in 1943 from a mouldy cantaloupe found in a Peoria, Illinois fruit market by USDA lab tech Mary Hunt (nickname 'Moldy Mary'). This strain produced 200x more penicillin than Fleming's original isolate. Every gram of penicillin made since descends from this single cantaloupe. See Moldy Mary and the Peoria Cantaloupe. - **Penicillium rubens**: the species Alexander Fleming actually isolated from a contaminated petri dish in 1928 (reclassified in 2011 from *P. notatum* based on genomic analysis). Lower penicillin yield than P. chrysogenum. - **Penicillium roqueforti**: blue-veining mould of Cheese Rind Microbiology including Roquefort, Gorgonzola, Stilton. - **Penicillium camemberti**: white bloomy rind of Camembert and Brie. Heavily domesticated — commercial strains are nearly clonal. - **Penicillium nalgiovense**: white mould on traditional salami and cured sausages. - **Penicillium glaucum**: also used in blue cheese; historically the mould used in traditional Auvergne cheesemaking. - **Penicillium expansum**: pathogen causing blue rot in apples, pears, produces the mycotoxin patulin. - **Penicillium digitatum**: green mould on citrus, responsible for most pre-retail citrus spoilage. ## Industrial uses beyond penicillin - **Enzymes**: lipases, proteases, amylases from Penicillium species are used in detergents, baking, brewing, textiles. - **Organic acids**: citric acid, gluconic acid production. - **Cholesterol drugs**: compactin and lovastatin precursors were isolated from Penicillium and Aspergillus species. - **Griseofulvin**: antifungal isolated from *P. griseofulvum*. - **Mycophenolic acid**: immunosuppressant isolated from *P. brevicompactum*, still used in transplant medicine. ## Taxonomy and relatives Penicillium belongs to the phylum Ascomycota (sac fungi) — same group as truffles, morels, Saccharomyces brewer's yeast, and most pathogenic moulds. Close relatives: - **Aspergillus**: the other major industrial/pathogenic mould genus. Source of soy sauce fermentation (A. oryzae), koji for sake, and many medical/industrial compounds. Also aflatoxins (A. flavus, major grain contaminant). - **Talaromyces**: former Penicillium species reclassified based on teleomorph (sexual stage). Penicillium differs from Dandruff Biology and the Malassezia Mechanism (a basidiomycete — club fungus, related to mushrooms) despite both being 'moulds' colloquially. Ascomycete vs basidiomycete divergence is ~600 million years old. ## History Mouldy bread and cheese were used for wound care in many cultures long before penicillin's isolation — see Moldy Bread as Pre-Modern Antibiotic. Fleming's 1928 accidental discovery was the scientific identification of the active agent; the folk knowledge that 'certain moulds help wounds' had been around for millennia. From Fleming's 1928 paper to first clinical use was 12 years (Florey and Chain's Oxford work, 1940-1941). Mass production required the Peoria USDA lab's deep-tank fermentation technique, the P. chrysogenum strain, and wartime industrial mobilisation. By D-Day 1944 penicillin was saving Allied soldiers' lives at scale.