mold

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Introduction References & Edit History

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Observe time-lapse photography of Penicillium mold releasing penicillin to its surroundings

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mold

fungus

Also known as: mould

Written and fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: May 10, 2025 • Article History

Also spelled:: mould

Key People:: George Wells Beadle; Edward L. Tatum

Related Topics:: Rhizopus; Aspergillus; Penicillium; Neurospora; Fusarium

On the Web:: National Center for Biotechnology Information - PubMed Central - Mold, Mycotoxins and a Dysregulated Immune System: A Combination of Concern? (May 10, 2025)

News •

The next superbug threat is already here. It’s going to be even harder to overcome • May 6, 2025, 8:11 AM ET (CNN)

Moldy food, used underwear: inside the US prisons where Trump is jailing immigrants • May 3, 2025, 4:53 AM ET (The Guardian)

peach moldMagnified view of peach mold (*Rhizopus*).

mold, in biology, a conspicuous mass of mycelium (masses of vegetative filaments, or hyphae) and fruiting structures produced by various fungi (kingdom Fungi). Fungi of the genera Aspergillus, Penicillium, and Rhizopus form mold and are associated with food spoilage and plant diseases.

This article was most recently revised and updated by Kara Rogers.