INTERACTIONS OF WOOD DECAY FUNGI WITH OTHER MICROORGANISMS, WITH EMPHASIS ON THE DEGRADATION OF CELL-WALLS

Interactions of two wood decay fungi, Lentinula edodes and Pleurotus o streatus, with other wood inhabiting microorganisms were investigated on agar and in fagaceous wood, primarily by scanning electron microsco py. Micromorphologically, there were two principal modes of cell wall degradation: (i) selective removal of amorphous wall components, follo wed by the degradation of skeletal microfibrils, and (ii) simultaneous degradation of all wail components. These two modes were observed in three different degradation systems: (i) sapwood wall degradation by t he wood decay fungi, (ii) hyphal wall degradation by mycoparasitic Tri choderma, and (iii) hyphal wall degradation by pathogenic bacteria. Th e simultaneous-type wall degradation in the systems i and ii was usual ly caused by hyphal tips. In addition to the three systems, bacterioly sis by the wood decay fungi was also studied. The bacterial cell walls , as well as microfibril bundles of wood cellulose and fungal chitin, were all fragmented into minute granules at later stages of microbial degradation and the granules were further degraded into smaller units. Frequency of occurrence and strength of mycoparasitic activity of Tri choderma harzianum were influenced by the degree of wood decay where t he interaction occurred. Presence of both cellulose and chitin microfi brils apparently enhanced the mycoparasitic activity. In Quercus wood, P. ostreatus showed a unidirectional growth toward bacterial colonies , which formed as the result of decomposition of dead nematodes, and c onsumed the unidentified bacteria. In nitrogen-deficient wood, fungal and bacterial cell walls may serve as an important reservoir of nitrog en for wood inhabiting microorganisms.