Biodeteriogenic and toxigenic agents on 17th century mural paintings and façade of the old church of the Holy Ascension (Veliki Krčimir, Serbia)

Abstract

Biofilm forming microbial community dwelling on the surface of façade and biodeteriorated 17th century wall paintings of the old Church of the Holy Ascension (Veliki Krčimir, Serbia) was evaluated through microscopic analyses, in order to detect toxigenic agents and assess potential damage caused by biodeteriogens. Initial optical examination of adhesive tape samples revealed complex microbial community flourishing on deteriorated mural surfaces highly enriched with inorganic impurities and organic contaminants of plant and animal origin. A variety of fungal structures, such as melanized hyphae, chlamydospores, fruiting bodies, as well as spores for sexual and asexual reproduction, were predominant in all samples analysed. In addition, among actively growing micromycetes, dematiaceous microcolonial fungi and toxigenic Chaetomium and Cladosporium species were most frequent. Scanning electron microscopy analysis revealed the presence of actinomycetes and highly developed mycelium network within the plaster and paint layers, as well as numerous Cladosporium-like conidial chains and Chaetomium lemon shaped ascospores. Such findings confirm our hypothesis that pulverization of painted layers was most likely due to hyphal penetration and formation of fruiting bodies and other fungal structures. Interestingly, although several green algae were documented on the surface of wall paintings and façade, no cyanobacteria were observed in any of the analysed samples.