Bacteria protect ancient paintings from bacteria that eat pigments

The pigment-eating bacteria are one of the reasons for the devaluation of priceless paintings, but other bacteria can help us protect them.

Like our bodies, oil paintings are home to a community of microorganisms, but only a few studies have tried to show their properties. To learn more about the microbes living in the pictures , Elisabetta Caselli from Ferrara University, Italy, and colleagues sampled small portions of Incoronazione della Virgine, a work completed in 1620 by the painter Italy, Carlo Bononi. This painting was hung on the ceiling of the Basilica of Santa Maria in Vado, Ferrara until an earthquake destroyed the church in 2012.

Bacteria were discovered on the picture: The samples were obtained from the front (a, b, c) and the back (d, e, f) of the picture - (Photo from Caselli et al, 2018).

The researchers isolated countless strains of Staphylococcus and Bacillus bacteria that once inhabited the picture, as well as the fiber-like fungus from just four bacteria, including Aspergillus, Penicillium, Cladosporium, and Alternaria. They also identified pigments such as red and yellow soil and red lac - may be nutritional sources for microorganisms.

As a microbiologist, Caselli has spent many years researching ways to eliminate harmful bacteria in many hospitals. Her research team discovered that detergents containing spores of harmless Bacillus bacteria could neutralize the development of pathogens, so they tried the same method to help preserve paintings.

Their Bacillus treatment method almost completely blocked the growth of bacteria and fungi extracted from the picture. According to Caselli, they also need to conduct more in-depth tests to ensure that the treatment will not harm the picture itself.

Caselli believes that a detailed analysis of the bacterial population on paintings can become an important part of future recovery efforts.'As a starting point, the Bacillus compound can be used as a mild alcohol solution on the reverse side of the painting, protecting this surface from potentially dangerous bacteria'. This method has been successfully used on stone artworks.