Description:
<jats:title>Summary</jats:title><jats:p><jats:styled-content style="fixed-case">L</jats:styled-content>eonardo da <jats:styled-content style="fixed-case">V</jats:styled-content>inci'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 (<jats:styled-content style="fixed-case">SEM</jats:styled-content>) imaging and molecular techniques. The fungus <jats:styled-content style="fixed-case"><jats:italic>E</jats:italic></jats:styled-content><jats:italic>urotium halophilicum</jats:italic> was found in foxing spots using <jats:styled-content style="fixed-case">SEM</jats:styled-content> 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 <jats:styled-content style="fixed-case"><jats:italic>A</jats:italic></jats:styled-content><jats:italic>cremonium</jats:italic> sp. colonizing the drawing.</jats:p>