Transmission electron microscope observations of white rot caused by Trametes hirsuta with respect to osmiophilic particles

Degradation of pinewood by the white rot fungus Trametes hirsuta was investigated with the transmission electron microscope. Decay of the cell walls was not limited to the areas around the hyphae, but occurred over the entire lumen surface, resulting in a thinning of the cell walls towards the middle lamella. Occasionally, locally restricted degradation was observed. A change in electron-density suggested an enzymic attack on one of the wood components in the cell wall. In the initial phase of attack aggregates of osmiophilic particles were found on the lumen surface as well as around the hyphae and within the protoplasm of the hyphae. In later stages of decay they appeared, though in smaller numbers, in the places of intensive decay. They were never observed in the cell wall. Two theories as to their origin are discussed.