Academic Paper from the year 2016 in the subject Biology - Ecology, , language: English, abstract: The oyster mushroom, Pleurotus spp., is edible. About seventy species of Pleurotus spp. have been recorded. Many oyster mushrooms are primary decomposers of hardwood trees found worldwide. Thus, it can be cultivated on a wide variety of substrates containing lignin, cellulose and hemicellulose. It must obtain nutrients from such organic sources as dead organisms since they had absorbed nutrients after digesting large molecules into smaller units because of their secreted enzymes; thus, it has been grown in Iraq on various agro-wastes in the wild, or manually on cardboard, date palm wastes, and tree sawdust. Since ancient times, macrofungi have been used as a valuable food source and as traditional medicines around the world. The fungi constitute an important source for some compounds including enzymes and antibiotics. Consequently, the antimicrobial activity of various polysaccharides from medicinal mushrooms is being reevaluated in relation to their clinical efficacy, given that such compounds would be expected to function to ward off bacterial and fungal infections resistant to current antibiotics. Medicinal mushrooms are able to synthesize a great amount of secondary metabolites that present anti-tumoral, antiviral, anti-inflammatory, antibacterial, antifungal and anti-yeast activities. This study evaluated the antifungal activity of four fruiting bodies of oyster mushroom harvested from three agro-substrates in vitro.