Mycological and ultrastructural studies to evaluate biodeterioration of mural paintings : detection of fungi and mites in frescos of the Monastery of St. Damian in Assisi

The role of fungi in the biodeterioration of frescos has been investigated by microbiological and ultrastructural techniques. With this aim, the mycoflora present on samples taken from deteriorated indoor wall paintings (frescos) in the Monastery of St Damian in Assisi was isolated and identified. The results showed that the fungal colonization of the two paintings ‘Crocifisso con Francesco giovane’ and the ‘Mensa di S. Chiara’, located inside St Clare's Refectory, was mainly due to Cladosporium, Aspergillus, Alternaria, Penicillium and Fusarium genera. Although considered not uncommon in frescos, their direct involvement in enzymatic degradation of paints was not confirmed. Interestingly, the presence of mites in proximity to actively growing fungal mycelium, as revealed by scanning electron microscopy, although considered an example of parasitic nutritional relation, could also suggest a metabolic interaction resulting in the synthesis of biodeteriogenic substances.