MadSci Network: Medicine

RE: Penicillin

Area: Medicine
Posted By: Lynn Bry, MD/PhD Student, Molecular Microbiology
Date: Fri Nov 1 16:05:34 1996

Penicillin comes from a fungus called Penicillium. It is a chemical produced by the organism as it grows. Many fungi live in the soil or other environments where they compete with bacteria for food and nutrients. One theory suggests fungi evolved the ability to produce these compounds to 'wipe out the competition,' so to speak.. Many classes of the antibiotics we use today - penicillins, aminoglycosides (gentamycin, neomycin) and macrolides (erythromycin) were identified in soil fungi.

In 1928 Alexander Fleming discovered the antibiotic-properties of Penicillium. In a less than tidy lab he noticed that a petrie plate with bacteria on it was also growing a contaminating fungus. The fungal colonies were surrounded by a zone of inhibition where no bacteria grew. Crude extracts of this fungus had the ability to kill different microbes. In the 1930s an Australian named Howard Florey worked further to purify penicillin. Both he and Alexander Fleming won the 1945 Nobel Prize in medicine for their work.

The strain of Penicillium characterized by Fleming did not produce great quantities of the antibiotic. I believe it was some years later that a strain was isolated from a rotten melon that produced greater amounts of penicillin when cultured. The fungus was grown in industrial-sized fermentation vessels to generate enough material for isolating sufficient quantities of penicillin. Knowledge of penicillin's chemical structure (the active part of penicillin lies in a structure known as a beta-lactam ring) allowed people to develop new antibiotics with slight structural variations producing different ranges of activity against specific microbes. This long train of research and development has led to many of the antibiotics we use today, in particular the classes of cephalosporins which share many chemical properties with penicillins.

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