Combining an innovative non-invasive sampling method and high-throughput sequencing to characterize fungal communities on a canvas painting

The present study describes the diversity and composition of fungal communities on a 1960's canvas painting by the iconic Portuguese artist Paula Rego. Optical microscopy (OM) and Scanning Electron Microscopy (SEM) were employed to check for the presence of fungal stains and structures on pre-selected sampling areas of the painting. A non-invasive sampling method was developed, consisting in smooth vacuuming of the selected sampling points and therefore preventing any damage to the artwork. The fungal communities were characterized by high-throughput sequencing of the Internal Transcribed Spacer 2 (ITS 2). The classes Dothideomycetes, Eurotiomycetes, Sordariomycetes, Agaricomycetes, Microbotryomycetes and Tremellomycetes were identified across all the painting sampled points. Statistical analysis using the Jaccard Similarity Index showed that the samples taken from the painting were not similar to each other. The combination of non-invasive sampling and high-throughput sequencing unveiled useful information about the fungal communities dwelling on this artwork. This represents a methodological advance for non-invasive sampling of delicate cultural heritage materials. To date, this is the first study applying such molecular technology for fungal identification on a canvas painting.