Oxalate was found to accumulate in liquid culture media from the growth of the white-rot basidiomycetes Coriolus versicolor, Heterobasidion annosum, Pleurotus florida and Phanerochaete chrysosporium. Whereas little oxalate accumulated during active growth, millimolar concentrations of oxalate were detected in culture media during the stationary phase. The basidiomycete Agaricus bisporus, the cultivated mushroom, also accumulated oxalate in its culture medium in the stationary phase. In comparison, the brown-rot fungi Amyloporia xantha, Coniophora marmorata, C. puteana and Poria vaporaria accumulated oxalate in the primary metabolic phase and throughout growth up to 35 days. Oxalate accumulation (0.04-10.0 mM) in whiterot cultures did not lower the pH of the medium during growth, whereas in brown-rot cultures oxalate (2.0-20.0 mM) reduced the media pH during growth. Cultures of Agaricus bisporus, C. puteana and Coriolus versicolor grown on solid media containing high levels of calcium (50 or 100 mM calcium chloride) produced calcium oxalate crystals to varying extents on the surface of the hyphae.

The use of immunogold-cytochemical labelling techniques in electron microscopy of wood infected by basidiomycete fungi has assisted in the elucidation of the localisation of enzymes which degrade lignocellulose. The use of specific immunocytochemical techniques is discussed with respect to the authenticity and accuracy of the methods, the use of adequate controls in the gold-labelling procedure, and the immunospecificity of the antibodies.Localisation of the lignin-degrading enzymes, lignin-peroxidase and laccase, has shown that these enzymes do not bind to wood cell walls unless the process of decay has already commenced. Similarly localisation of cellulases Endoglucanase II (EGII) and Cellobiohydrolase I (CBHI) has shown that these enzymes only bind to exposed ends of cellulose fibrils and to partially degraded areas of the wood cell wall. ~-Glucosidase is always immobilised within the extracellular polysaccharide layer surrounding fungal hyphae.This review postulates that there is regulation of the release sequence of these lignocellulolytic enzymes defining the spatial arrangement between the hyphae and the wood cell wall. This hypothesis is presented diagrammatically.

The degradation of wheat straw, during composting, to produce the growth substrate for the edible mushroom (Agaricus bisporus), and subsequent colonisation by the fungal hyphae, was studied by electron microscopy which revealed an ecological succession of micro‐organisms, initially dominated by a largely bacterial flora with few fungi. Later in the composting process actinomycetes were dominant. The initial rise in numbers of vegetative bacterial cells was followed by a steady decline and the appearance of spore forms. Several modes of microbial attack were observed. The most rapid degradation occurred initially on the cuticle and in the phloem and spread to a general degradation of all the plant tissue types present. Microbial attachment on the plant cell walls was non‐uniform. As a result of these processes many of the plant fibres became separated but the final material still retained considerable structural integrity. Agaricus bisporus mycelium rapidly covered the surface of the straw but colonised the internal straw tissues more slowly. Surface‐growing hyphal cells were encrusted with needle‐like crystals presumed to be calcium oxalate.

The effects of two cooling methods and two storage temperatures on mushroom quality, anatomy and weight loss were compared. Mushroom quality was assessed as a function of cap browning and hyphal structure. Storage of mushrooms at 5°C conserved quality and reduced weight loss as compared with those stored at 18°C. No differences in quality or hyphal structure were found between vacuum and conventionally cooled mushrooms when subsequently held at 5°C; when cool storage was followed by a period at 1 8 T , vacuum-cooled mushrooms were significantly better with regard to colour (enzymic browning) than those conventionally cooled. The rate of weight loss during storage at 5°C was greater for vacuum-cooled than conventionally cooled mushrooms.

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