Temperature regulation of extracellular proteases in ectomycorrhizal fungi(Hebeloma spp.) grown in axenic culture

Strains of Hebeloma representative of different climatic zones were grown i n axenic culture at either 2 degrees C and 22 degrees or 6 degrees and 22 d egrees. Culture filtrates were assayed for proteolytic activity using FITC labelled BSA as a substrate. Assays were run between 0-37 degrees. Growth a t low temperature induced greater proteolytic activity (g(-1) D.W. mycelium ). Many of the strains produced protease(s) which retained significant acti vity at temperatures as low as 0 degrees, and a thermal optimum between 0-6 degrees with a second optimum at higher temperature. The results are discu ssed in relation the nutrient acquisition potential of ectomycorrhizal fung i at low temperature and the contribution such cold active proteases might make to the soil enzyme pool.