Scientists discover rare Japanese bacteria on Rembrandt painting

Scientists from the Rijksmuseum in Amsterdam and the Artis-Micropia museum of microorganisms discovered unexpected life forms on Rembrandt’s painting, The Night Watch.

Researchers are analyzing the biological life on the surface of the famous 17th-century Dutch masterpiece to better understand how to preserve the work. The team is collecting 60 samples from 10 different locations on the canvas using sterile cellulose discs.

These discs press against the surface to pick up microbes, which are then grown and observed on Petri dishes. Early results identified common bacteria found on human skin, soil, and plants, including Staphylococcus epidermidis and Micrococcus luteus. They also found Lysinibacillus sphaericus, a soil bacterium capable of surviving in environments with high concentrations of heavy metals. The most surprising finding was the presence of Microbacterium saccharophilum.

This specific species was first described in 2013 from a sugar refinery in Yokohama, Japan. Microbiologist Eline van Bloois stated that the team did not expect to find this bacterium and cannot explain its presence on the painting. She noted that the discovery does not mean the bacteria have been on the canvas since the 17th century, though determining exactly when they arrived will be difficult.

These microbiological tests are part of Operation Night Watch, a major research and conservation project that began in 2019. Previous stages of the project revealed hidden sketches, changes in the original composition, and layers of lead and arsenic pigments. The current study will continue for about six months to help conservators plan future maintenance. Since 2024, specialists have also been removing a varnish layer from the 1970s to clean the surface.