Determining the Source of Biodeterioration of the 16th Century Icon Deesis Tier of 13 Figures from the State Tretyakov Gallery

The icon of the Novgorod school of painting from the end of the 16th century, Deesis tier of 13 figures was received to the storage fund of the State Tretyakov Gallery (Lavrushinsky Lane 10, Moscow) and had presumable foci of biodeterioration, which led to partial loss of the paint layer and other damage. In the current work, microbiological samples were collected from problem and control zones, fungal and bacterial cultures were obtained, and genotyping was performed using hypervariable regions of rDNA, V3/V4 of bacteria, and ITS1, ITS2 of fungi. The identified bacteria belonged to the classes Gammaproteobacteria (Stenotrophomonas sp., Pseudomonas sp.) and Bacilli (Bacillus sp.). All fungal isolates belonged to Iodophanus sp. and had the morphology characteristic of this species. In order to reveal the ability to biodeteriorate, set of mock layers was created with individual materials used in the manufacture of the icon. Microorganisms isolated from the icon were inoculated onto the mock layers; it was shown that Iodophanus sp. is capable to effectively degrade the studied painting materials, such as sturgeon glue, pavoloka, yolk emulsion, and tempera paint ocher. Our work shows for the first time that a representative of the Pezizaceae family is capable of occupying such an unusual ecological niche as paintings and icons, in particular. The topic of our further research is related to the targeted selection of antiseptics for restoration work on the icon Deesis tier of 13 figures.