With respect to the temperature, Table 3.8 shows the cardinal points for some wood fungi. A comprehensive investigation was completed in 1933 grouping the species into low-temperature (optimum 24 °C and below), intermediate-temperature (optimum between 24 and 32 °C), and high-temperature group (optimum above 32 °C) (Humphrey and Siggers 1933).
For three species, e.g., Gloeophyllum sepiarium, minimum, and maximum temperatures were already determined (Lindgren 1933). It has to be considered, however, that considerable differences can exist between isolates of a species .
Generally, it applies to wood fungi: The minimum is usually at 0 °C, be-cause below the freezing point there is no liquid water available necessary for metabolism. Exceptions of growth below 0 °C are possible, if the freezing point is decreased, e.g., by trehalose and glycerol or other polyhydric alcohols as anti-freeze agents which prevent ice-crystal formation within the hypha (Jen-nings and Lysek 1999). In some blue-stain and mold fungi, the lower limit for mycelial growth is at 7 to 8 °C (Reif31997). Above the lower limit, the "reac-tion speed-temperature rule" begins to take effect, as in a certain temperature range, enzyme activity runs two to four times faster by increasing the tempera-ture of about 10 °C (Q10 value).
Frequen4 the optimum lies, depending on the species (and isolate) between 20 and 40 °C and thermophilic Thermotolerant fungi, e.g., Phanerochaete chrysosporium and other fungi growing in wood chip piles, prefer the mesophilic range, toler-ate however still 50 °C. The maximum for mycelial growth and wood damage by most wood fungi is often at 40-50 °C, because then the protein (enzyme) denaturing by heat takes effect. Fungi, however, may exhibit a change in gene expression, which leads to the synthesis of "heat-shock proteins (hsp)".
The hsps appear to prevent and repair general damage, denaturation and aggrega-tion of other cellular proteins, as they are not only induced by heat, but also by heavy metals and oxidants (Jennings and Lysek 1999). Serpula lacy possesses a characteristic, which can be used for identi-fication. With the optimum of about 20 °C, slight growth still at 26-27°C, and growth stop at 27 -28 °C, the fungus differs from the other indoor wood decay fungi, like the Cellar fungus and the white polypores, as well as from other Serpula species, because, e.g., S. himantioides still grows at 31°C.
There are, however wild Himalayan isolates of )s. Iinacarydrndiatinosnthiant S. olawcerydlisilaignhstaglsroowththe at 32 °C (Paifreyman and Low 2002 .
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