Oil paintings on canvas stored under certain environmental conditions are often contaminated by moulds. Many of the materials on the paintings are of organic origin and therefore useful for fungal degradation, moulds can also attack canvas supports. Most important limiting environmental factor against fungal growth is the constantly limited availability of water. In the master thesis we studied fungi on four mouldy paintings on canvas painted with oil paints between 265 and 504 years old, all from Slovenian churches. Using classical culture techniques, we determined cell density on the sampled surfaces and isolated pure cultures of fungi, which were identified to species level using molecular markers. Cultivation and short-read sequencing of ITS2 from total DNA of samples gave a similar result in identification of fungi with minor discrepancies; xerophillic species of the genus Aspergillus and xerotolerant species of the genera Penicillium and Cladosporium prevailed on the surfaces of the paintings. Samples taken from painting’s surfaces by adhesive tape were stained with different sets of fluorescent dyes to determine cell viability. We found that the proportion of non-viable fungi on the prints was high and that the spores stained non-specifically. To determine the species and proportion of viable fungi on the paintings, we used quantitative polymerase chain reaction (qPCR) and short-read sequencing of the ITS2 sequence on samples treated with the photoreactive dye PMAxx. This dye prevents DNA replication from non-viable cells in the PCR reaction. In fungal pure cultures, we have shown that the dye PMAxx works at a concentration of 25 μM s and that it can be used also in other high-performance genetic methods.
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