The oyster mushroom on your plate hunts and digests tiny worms
Oyster mushrooms look gentle, fanning out from dead logs in pale shelves. Underground, their threads trap and digest nematodes, microscopic roundworms, apparently to harvest nitrogen. Every major lineage of the species does this, making it one of at least 700 known worm-eating fungi, and a popular dinner ingredient.
Both its names describe its shape. Pleurotus means side-ear, for the stem that grows off to one side of the cap, and ostreatus refers to the cap's resemblance to an oyster shell, and perhaps to its slippery feel. Caps range from 2 to 30 centimetres across, white to grey or brown, with whitish gills and a faint bitter-almond smell from benzaldehyde. Foragers need care: toxic lookalikes include Omphalotus nidiformis in Australia and the western jack-o'-lantern mushroom in North America.
The species grows across temperate and subtropical forests worldwide, though not in the Pacific Northwest, where close relatives take its place. It is a white-rot fungus that breaks down dead wood, especially beech and other broadleaf trees. It often appears on dying trees, but it seems to feed on wood already dead rather than killing its host, returning minerals to the soil in forms other organisms can use. It also accumulates lithium, and some beetle species depend on it as food for their larvae.
Farming it began in Germany during the First World War as an emergency food source, and it is now grown commercially around the globe. Czech, Polish and Slovak cooks use it much like meat in soups and stews, or breaded as a vegetarian cutlet, while it is prized in Chinese, Japanese and Korean cooking and sold deep-fried by Indonesian street vendors. Young specimens taste mild, with a hint of anise; older ones turn tough and acrid.
Its appetite for tough materials has industrial uses. In one trial it converted 95 percent of diesel oil in contaminated soil into non-toxic compounds, and it can grow on and degrade certain plastic bags. It is also used to make mycelium bricks, furniture and leather substitutes, and it contains lovastatin, a cholesterol-lowering drug.
Source: Pleurotus ostreatus
