Osmiophilic particles as a typical aspect of brown and white rot systems in transmission electron microscope studies

Abstract

Transmission electron microscope investigations of wood decay by the brown rot fungi Poria placenta and Serpula lacrimans and the white rot fungi Trametes versicolor and Sporotrichum pulverulentum showed that the distribution of the osmiophilic particles in brown-rotted and white-rotted wood conformed to that previously established for other species. When pinewood is degraded by brown rot fungi osmiophilic particles are densely distributed in all cell wall layers. This distribution correlates with the rapid depolymerisation of carbohydrates over the entire cell wall. In white-rotted pinewood osmiophilic particles are found on the surfaces of the cell wall and of cell wall remnants but never within the cell walls. That osmiophilic particles within and around hyphae outside degraded woodblocks and even in and on hyphae 40 mm from the wood suggests that they are not degradation products of a wood component but are produced by the fungus. However their aggregation in regions of strong wood decay suggests that they are associated with this process. Contrary to the literature brown rot fungi have been found capable of lignin metabolism causing complete disintegration of wood cell walls, middle lamella and the cell corners.