WOOD DECAY BY THE WHITE-ROTTING BASIDIOMYCETE PHYSISPORINUS-VITREUS FROM A COOLING-TOWER

Timbers in cooling towers are mainly attacked by soft rot causing fung i which belong to Ascomycetes and Deuteromycetes. The basidiomycete Ph ysisporinus vitreus degraded water-saturated timber as fibrous white-p ocket rot in a cooling tower in which water treatment had been changed from chlorine to ozone. In the laboratory, the fungus revealed a rema rkable wood decay pattern. In crosswise piled, water-saturated pine sp ecimens it attacked only those parts not surrounded by air. The decay occurred as small longish delignified white pockets, preferentially in the earlywood. Transmission electron microscopy of unstained sections showed some electron density in the hyphal extracellular layer and in the wood cell wall beneath a hypha. Contrasted with KMnO4 staining, t hese regions became more pronounced which may indicate presence of lig nin degradation products. UV-microspectrophotometry of these areas exh ibited an increased absorbance. Many decay pockets were black due to m anganese (Mn) deposits. Mn determination by inductively coupled plasma emission (ICP) revealed up to 518 ppm Mn. TEM/EDXA showed Mn deposits in the hyphal extracellular layer, on the cell wall surface and in th e inner S-2 layer beneath a hypha. The Mn may be related to the lignin attacking peroxidases.