“Of course, we found a lot of bacteria linked to the skin microbiome,” Piñar explains. “So when you touch it, you leave your own microbiome in it.” You might be thinking: does that mean we now know what was crawling on Vinci’s hands when he drew these masterpieces? Unfortunately, no, because the drawings have been manipulated by many, many other people in the five centuries since the master drew them. And to be clear, this genetic sequencing didn’t tell researchers whether all of these bacteria were dead or alive, just that they were present in one form or another.
Among microbes in human skin, researchers found high levels of the bacterial genus Moraxella, in particular Moraxella osloensis, who is responsible for the stench of dirty laundry. In addition, they detected the infamous bacteria Salmonella and E. coli., which cause disorders in the human intestine. They also found species of bacteria specific to the guts of greylag flies and fruit flies, which means insects brazenly defecate on priceless works of art – at least until someone places them in boxes. Spotlessly clean drawers for storage, or behind glass where they are displayed. , sealed and stored at the perfect temperature and humidity. “As the designs are preserved today, there’s no way for the insects to get in and, you know, do their business there,” Piñar says. “This is no longer possible. So you have to think that this could be from the days when designs weren’t stored the way they are now. “
Piñar and his colleagues also found Aspergillus, a mold that dangerous for some people to inhale, and detected species of the genus Penicillium, the fungus that gave us penicillin. More worrying for works of art and the restorers who handle them, analysis found the fungus Alternaria, known as a “paper spoiler” for its habit of … spoiling paper. It is also an allergen which can be dangerous to inhale.
The team also discovered the fungi responsible for the “scorching” of the paper, or the yellow-brown spots that form over the years. In addition to DNA analysis, the researchers scoured the surface of the drawings with a microscope and spotted encrustations of calcium oxalate crystals produced by these fungi. “So you can deduce a lot from that with this microscopic analysis and complement the molecular analysis that we’re doing here very well,” says Piñar.