The famous fungus that led to the discovery of penicillin is going up for auction

A slice of medical history.
A slice of medical history.
Image: Stringer/Reuters
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Lot 92 at Bonhams auction house isn’t much to look at—just a blob of mold encased in glass and plastic. But this mold is famous. It’s part of the original culture of Penicillium chrysogenum that led to bacteriologist Alexander Fleming’s 1928 discovery of the antibiotic penicillin.

Fleming preserved the specimen himself in his lab. It’s expected to sell at a March 1 auction for at least £4,000 (about $5,000), a price that reflects a surprising abundance of historic mold on the market.

When Sotheby’s offered a similar mold medallion in 1996, it was believed to be one of only a very few surviving specimens. The drug manufacturer Pfizer bought it for £23,000 (about £41,000 today, or $51,000).

Days after the BBC aired a story on the sale, the Alexander Fleming Laboratory Museum at St. Mary’s Hospital in London got a call from a woman who also had a Fleming mold medal and wanted to donate it. As more medallions surfaced over the decades, historians figured out that Fleming handed out mold like calling cards.

Award Fleming an honorary degree? You got mold. Dedicated service in his lab? Mold. A special audience with a celebrity or royal? Again: mold.

After receiving his second mold medal in a matter of months, Prince Philip, Queen Elizabeth II’s husband, allegedly complained about getting “another of these bloody things” every time he and the scientist met, says Kevin Brown, curator of the Fleming museum and author of Penicillin Man: Alexander Fleming and the Antibiotic Revolution. (You can watch a video of one of their meetings. If this isn’t the prince’s first mold medallion presentation, he at least hides his irritation.)

“He thought that what they would most appreciate would be something connected with penicillin, which was the reason for the interest in him,” Brown says.

Fleming grew his gift mold on absorbent paper and pressed the samples between spectacle lenses sourced from his brothers’ optometry practice.

He had a playful attitude toward science. A painter on the side, Fleming made pictures by arranging differently-colored microbes on his petri dishes. It may even have been in one of these living artworks that he made his most famous discovery.