Penicillium spp. are a group of filamentous fungi that are ubiquitous in the environment. In 1929 Alexander Fleming published his work on the characterization of penicillin, the first widely used b-lactam antibiotic, from Penicillium notatum (now known as P. chrysogenum). Fleming's discovery stemmed from the observation that Penicillium contaminating his cultures readily inhibited other microorganisms. Fleming shared the 1945 Nobel Prize in Physiology or Medicine with Ernst Chain and Howard Florey for his work on penicillin. Other Penicillium spp. (e.g., P. roqueforti and P. camembertii) are of commercial importance for their use in cheese fermentation. Members of this genus are also linked to a variety of diseases including urinary tract, respiratory, and ear infections; keratitis; and endocarditis. The isolate in this image was cultured from equipment housed in the Moser Leather Tannery in New Albany, Indiana. The tannery may be converted to a museum and this work is part of a larger study to determine if fungi in the buildings pose a threat to visitors.

The Penicillium sp. was prepared by the slide culture method using potato dextrose agar (incubation at 25°C) and stained with lactophenol cotton blue. The image illustrates the brush-like conidial heads characteristic of Penicillium. Phialides (conidia-producing cells) are visible directly below the chains of conidia (brightfield microscopy; 400x magnification). Identification was done through visual inspection of morphology and confirmed by partial DNA sequence analysis of the ribosomal RNA gene. The figure can be used to illustrate the fine structure of the asexual cycle of Penicillium and to aid in the identification of unknown isolates.

References.

1. Fleming, A. 1929. On the antibacterial action of cultures of a Penicillium, with special reference to their use in the isolation of B. influenzae. Br. J. Exp. Pathol. 10:226-236.

2. Larone, D. H. 1995. Medically important fungi, 3rd ed. ASM Press, Washington, D.C.

3. Lechevalier, H. A., and M. Solotorowsky. 1974. Chemotherapy, p. 429-492. In Three centuries of microbiology. Dover Publications, New York, N.Y.