Architecture of the Agaricus bisporus spore wall

Abstract

Purified wall fragments of Agaricus bisporus spores were examined by electron microscopy untreated or after chemical and enzymatic digestion. The wall is composed of three layers (I, II, III): an electron-dense outer layer (380 nm), a moderately electron-dense middle layer (180 nm), and an almost electron-transparent inner layer (20 nm). Layer I has a smooth outer surface, is granular–amorphous, but also contains some fibrillar material. It has high resistance to alkali and acid and poor susceptibility to enzymic attack. Layer II consists of chitin fibrils embedded in a β-glucan – protein matrix. It is separated into two sublayers by a narrow central band of electron-transparent material. Layer III is amorphous and appears to be a mucilaginous type of substance.