IRG Documents Database and Compendium


Search and Download IRG Documents:



Between and , sort by


Displaying your search results

Your search resulted in 2 documents.


Suppression of aerial hypha formation by spent culture filtrate of a non-degradative strain of Postia placenta
1991 - IRG/WP 1498
ME20, a wild-type monokaryotic strain of the brown-rot fungus Postia placenta, does not cause significant weight losses in standard soil-wood block decay tests and fails to form aerial hyphae in liquid and agar culture. This abnormal morphological feature may be caused by the same aberrant physiology that prevents the strain from degrading wood efficiently. ME20 releases elevated levels of the autolytic enzymes laminarinase and protease into culture media. These autolytic enzymes may degrade the cell wall and hyphal sheath, thus preventing aerial hypha formation and limiting wood colonization. If abnormally high levels of autolytic enzymes suppress aerial hypha formation, any strain of Postia placenta grown in their presence should take on the appearance of ME20. MAD698, a standard floccose test strain of Postia placenta, was grown in fresh media containing increasing concentrations of filter-sterilized spent culture filtrate of ME20. Aerial hypha formation was strongly inhibited or prevented when the spent culture filtrate made up 40% or more of the medium. Spent media from MAD698 caused a similar effect but only at higher concentrations (80 and 100%). The suppression does not appear to be caused by extracellular autolytic enzymes since commercial preparations of laminarinase, chitinase, and protease did not reproduce this effect. The suppressive agent appeared in ME20 culture filtrate after only two weeks of growth. It has a molecular weight of less than 10,000 and is resistant to boiling. Additional research is needed to characterize ist nature, thus identifying a potential biorational inhibitor of wood-decay fungi.
J A Micales


The role of chitinase in bioprotectant activity against staining fungi
1996 - IRG/WP 96-10175
Chitin is an important structural component of the hyphae of many wood staining fungi and its disruption can lead to dramatic declines in their growth. A number of bioprotectants have been shown to produce chitinases in liquid cultures, but the role of these enzymes in bioprotection remains poorly understood. The levels of these enzymes was studied by inoculating ponderosa pine sapwood wafers with liquid cultures of either Serratia plymuthica or Trichoderma harzianum. The wafers were then inoculated with a mixture of wood staining fungi and incubated for 4 weeks at 23 to 25°C. The wafers were then evaluated for degree of stain prior to extraction and analyzed for chitinase activity. Chitinase activity appeared to increase with increasing degree of bioprotection for several isolates of Trichoderma harzianum, while the relationship was less clear with Serratia plymuthica.
J Liu, J J Morrell