Fluorescence in Situ Hybridization Technique: a Tool Useful for Detecting Cultural Heritage Biodeteriogens

Microorganisms such as Bacteria and Archaea can damage monuments and stone artworks through various mechanisms, including biofilm formation, chemical reaction with the substrate and production of pigments. The biogenic release of inorganic and/or organic corrosive acids is probably the best known and most commonly investigated biogeochemical damage mechanism concerning inorganic materials. For example, aerobic microorganisms producing respiratory carbon dioxide, which becomes carbonic acid, contribute to dissolving stone and forming soluble salts. Moreover, the production of organic acids, such as lactic, oxalic and acetic, has been associated with the dissolution of calcite in calcareous stones. For these reasons, the phylogenetic classification of microorganisms colonizing cultural heritage substrates is very important, in order to detect the taxa involved in biodeterioration and apply the appropriate countermeasures. Fluorescence in situ hybridization (FISH) technique is a rapid and highly valuable culture-independent molecular method for detecting and identifying individual microbial cells in environmental samples using rRNAtargeted oligonucleotide probes. When used for detecting and identifying Cultural Heritage biodeteriogens, the FISH method can be performed in two ways: on powdered samples from the surface studied or more recently on adhesive tape strips applied on the surface and immediately removed. In contrast to other identification approaches, the FISH method largely maintains the characteristics of the targeted microorganisms and makes it possible to have a mirror image of the whole microbial community of a sample.