Penicillium on grapes The powdery, greenish-gray fungus on the table grapes at the right (which had been stored for too long in a refrigerator) is a species of the genus Penicillium. This is the same genus from which the powerful antibiotic penicillin is derived. If you ever opened an old jar of jelly or jam and its surface was covered with a greenish mat, that was probably Penicillium, too.

In case you don't like to throw food away you will be happy to know that when you find Penicillium covering your favorite jam, the fungus itself is not poisonous and if the mold layer is removed the food will still be edible, assuming that something else hasn't spoiled it. Another big genus among the blue-green molds is Aspergillus, whose species aren't always so generous. They can cause ear and lung infections.