On the isolation of microcolonial fungi occurring on and in marble and other calcareous rocks

Several filamentous and microcolonial fungi (MCF) have been isolated from stone monuments and natural rock outcrops, mainly in the Mediterranean area. Most strains are characterized by melanin production. MCF proved to be meristematic; some showed dimorphic yeast-like growth. Meristematic development and melanin production is supposed to play a key role in the survival of MCF on white marble in dry and hot environments. Meristematic swelling of cells with thick cell-walls containing melanin and formation of endoconidia support their water independence and desensitivization against UV-radiation. MCF are therefore supposed to be the resident flora while filamentous fungi could only be contaminants. They are not lichenized, since no algae could be found in association with them. Optimal isolation techniques are discussed. Fungi are described after their in vitro morphology. The taxonomic status of these organisms is considered. Molecular investigations are in progress.