Half a death cap mushroom may hold enough toxin to kill an adult
The death cap causes about 90 percent of the world's fatal mushroom poisonings. Cooking and freezing do nothing to its toxins, it resembles prized edible species, and its smell starts out honey-sweet. It may have killed the Roman emperor Claudius in AD 54. The mushroom itself is immune to its own poison.
Amanita phalloides is native to Europe but has spread worldwide since the late 20th century, sometimes travelling with planted oaks, chestnuts and pines. It lives in partnership with the roots of broadleaved trees, forming ectomycorrhizae. Fruiting bodies emerge in summer and autumn from a white egg-like casing. Caps usually span 5 to 15 cm and are greenish, though olive, bronze and even white forms occur, so colour alone is no guide. Gills and stem are white, a floppy ring hangs below the cap, and a sac-like cup called the volva wraps the base, often buried in leaf litter.
Its danger lies partly in disguise. It looks like Caesar's mushroom and the straw mushroom, both widely eaten, and its cap peels easily, a trait sometimes wrongly thought to mark edible fungi. The odour begins faint and sweet but grows sickly and overpowering with age.
Two families of ring-shaped peptides do the damage: amatoxins and phallotoxins. Heinrich Wieland and Rudolf Hallermayer of LMU Munich isolated the amatoxins in 1941. The main one, alpha-amanitin, blocks RNA polymerase II, an enzyme needed to make messenger RNA, so affected cells can no longer build proteins and die. The liver takes the brunt because it meets the toxin first after digestion, and the kidneys also suffer. The fungus's own version of that enzyme is unaffected. Besides Claudius, Holy Roman Emperor Charles VI in 1740 is a suspected victim.
Naming took a century of revisions. Sebastien Vaillant described it in 1727 as a dirty-green, ring-stemmed, phallus-shaped fungus. Elias Fries called it Agaricus phalloides in 1821, and Johann Link fixed the current name in 1833. It is the type species of section Phalloideae, home of every deadly Amanita so far known, including the all-white destroying angels.
Source: Amanita phalloides
