MULTIPLE STRESS FACTORS AFFECTING GROWTH OF ROCK-INHABITING BLACK FUNGI

Black fungi, belonging to the Dematiaceae, with yeast-like growth patt erns, were isolated from rock surfaces in the Mediterranean. They tole rate high temperatures and sodium chloride stress although they are ne ither thermophilic nor halophilic organisms. Environmental stress fact ors not only affect growth velocity of the fungi but also the colony s hape. A shift of the smooth and flat colonies developed under optimal culture conditions to more clump-like growth similar to the colony sha pe on the natural rock substratum is caused by both high temperature a nd osmotic stress. The ''principle of uniformity'' is proposed as a ne w term to interpret specific morphotypes of pleomorphic fungi of diffe rent taxonomic assignment.