The microbial colonization of oil paintings. A laboratory investigation

Only a few bacterial and fungal species present in a soil extract grew and survived on painted canvases prepared utilizing the materials and following the recipes traditionally used for paintings. When pure cultures of these microorganisms were used to contaminate such canvases, microbial growth and survival were even more reduced. On the other hand, on this substrate, the bacteria isolated from a heavily contaminated XVIth century fresco grew to a limited extent, but remained viable for a much longer period of time. Unlike the bacteria isolated from soil, those isolated from the fresco were able to hydrolyse cellulose and proteins. It is thus possible that the capacity to utilize these macromolecules may favour microbial survival on paintings. Furthermore, the addition of phosphate strongly stimulates growth of all microbial species indicating that this anion is the limiting nutrient factor.