Scientists from Austria and Italy analysed seven sketches from the legendary Renaissance painter. They compiled a database of the bacteria, fungi and human skin microbes found within the 500-year-old pieces. Guadalupe Piñar and her team also found some microbes that could cause breathing difficulties and previously risked destroying the artwork.
Using specialist technology that had membranes attached to a suction cup, Ms Piñar’s team were able to “obtain all the information” without touching the da Vinci pieces.
They detected microbes from the artist’s portrait The Man in Red Chalk and other works, which they then used to make a database.
While some of their findings, such as “skin biome” – from when people had “touched it” – were not a surprise to the scientist, there were several other stomach-churning discoveries.
They detected Salmonella and E. coli bacteria, which can both cause food poisoning or serious infections if ingested.
Bacteria typically found in the guts of common flies and fruit flies were also discovered on some of the works – which meant insects had defecated on the pieces.
Leonardo da Vinci’s sketches have been discovered to contain bacteria, human skin and fly defecation
Leonardo da Vinci: Portrait of a Man In Red Chalk and six other pieces were studied by Ms Piñas
Her team also found high levels of bacteria genus Moraxella, which causes the foul smell often associated with dirty clothing.
Most concerningly, Ms Piñas and her colleagues found Aspergillus, a mould species that can be dangerous for some people to breathe in.
They also discovered a type of fungus that led Scottish scientist Alexander Fleming to develop the antibiotic penicillin.
Ms Piñas found Alternaria, a fungus that is responsible for spoiling paper and leaving yellow-brown spots – the allergen can also be dangerous to inhale.
In her scientific paper, published in Frontiers in Microbiology last week, she explained that microbes developed on the works prior to them being preserved more safely.
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Leonardo da Vinci: Some of the microbes discovered on the artist’s sketches
Nowadays, artwork is stored in extremely clean storage units or behind glass, where they are sealed to keep temperature and humidity at a level where it cannot cause degradation.
Ms Piñas explained: “The most important message is to identify the possible microbial risk in order to adapt the environmental conditions of storage.
“They cannot allow the germination or the proliferation of microorganisms, in this case the control of environmental parameters – such as temperature, humidity, and clean air.”
Massimo Reverberi, a microbiologist from the Sapienza University of Rome, told Wired that ensuring these perfect conditions was pivotal.
He explained: “It’s like saying, ‘OK, there’s an army in your country that has a weapon, and it can use this weapon to spoil your – in this case – artifact’.
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“And when there is a trigger – that could be global warming – it could start to do some of its spoiling activity.”
Two of the sketches were obtained from the Corsini Library in Rome and five from The Royal Library of Turin, both in Italy.
Ms Piñar and her team’s work was not able to detect whether the microbes were alive or dead – but just that they existed on the work.
She said: “We could see really that the microbiomes were grouping according to their geographical location.”
They were about to detect “more similarities” between the Turin drawings and two of the pieces from Rome.
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Ms Piñas added: “So actually there should be a geographical influence, or in the storage conditions of these places.”
Their work was made possible by a new nanopore genetic sequencing device that was developed by Oxford Nanopore Technologies.
The sequencer, which is small enough to fit into someone’s pocket, was praised for its portability and that it did not put the artwork at risk – as scientists did not touch the pieces.
Ms Piñas added: “In any other environmental study, you can go there, you can take kilos of soil or liters of water. But we cannot take samples
“So, theoretically, you can take the device everywhere and do the sequencing on-site – imagine also being able to sequence in museums or archives.”