Bioremediation at work: (Top photo and inset) Oyster mushrooms are growing on soil contaminated with oil (at 1–2% or 10,000–20,000 ppm). (Bottom photo) After 16 weeks, soil toxicity has been so greatly reduced—to less than 200 ppm—that plants, worms, and other species have established in it, while control piles remained toxic to plants and worms. Note that, even though oyster mushrooms are edible species, those grown in this application should not be eaten. Photos from Fungi Perfecti