title: Amid the possible causes of a very famous foxing: molecular and microscopic insight into Leonardo da Vinci's self-portrait.
abstract: Leonardo da Vinci's self-portrait is affected by foxing spots. The portrait has no fungal or bacterial infections in place, but is contaminated with airborne spores and fungal material that could play a role in its disfigurement. The knowledge of the nature of the stains is of great concern because future conservation treatments should be derived from scientific investigations. The lack of reliable scientific data, due to the non-culturability of the microorganisms inhabiting the portrait, prompted the investigation of the drawing using non-invasive and micro-invasive sampling, in combination with scanning electron microscope (SEM) imaging and molecular techniques. The fungus Eurotium halophilicum was found in foxing spots using SEM analyses. Oxalates of fungal origin were also documented. Both findings are consistent with the hypothesis that tonophilic fungi germinate on paper metabolizing organic acids, oligosaccharides and proteic compounds, which react chemically with the material at a low water activity, forming brown products and oxidative reactions resulting in foxing spots. Additionally, molecular techniques enabled a screening of the fungi inhabiting the portrait and showed differences when different sampling techniques were employed. Swabs samples showed a high abundance of lichenized Ascomycota, while the membrane filters showed a dominance of Acremonium sp. colonizing the drawing.
authors.affiliation: Department of Biotechnology, Vienna Institute of Biotechnology (VIBT), University of Natural Resources and Life Sciences, Muthgasse 11, Vienna, 1190, Austria.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Piñar
authors.affiliation: Department of Biotechnology, Vienna Institute of Biotechnology (VIBT), University of Natural Resources and Life Sciences, Muthgasse 11, Vienna, 1190, Austria.
authors.forename: Hakim
authors.initials: H
authors.lastname: Tafer
authors.affiliation: Department of Biotechnology, Vienna Institute of Biotechnology (VIBT), University of Natural Resources and Life Sciences, Muthgasse 11, Vienna, 1190, Austria.
authors.forename: Katja
authors.initials: K
authors.lastname: Sterflinger
authors.affiliation: Istituto Centrale per il Restauro e la Conservazione del Patrimonio Archivistico e Librario (ICRCPAL), Ministero per i Beni e le Attivita Culturali, Via Milano 76, Rome, 00184, Italy. flavia.pinzari@entecra.it.
authors.forename: Flavia
authors.initials: F
authors.lastname: Pinzari
mesh_terms: D004783:Environmental Microbiology; D005658:Fungi / Q000145:classification / Q000235:genetics; D054892:Metagenome; D056186:Metagenomics; D008855:Microscopy, Electron, Scanning; D010151:Paintings; D010802:Phylogeny