Scientists find DNA of bacterium behind London's Great Plague

Five skeletons found to contain 1665 Great Plague bacteria (Crossrail).

Scientists have recovered DNA from the bacterium that caused London’s 1665 Great Plague by studying the teeth of five skeletons.

This is the first time that plague DNA from 17th-century Britain has been pinpointed and marks a breakthrough in Great Plague research. The 1665 outbreak was Britain’s last major bubonic plague outbreak and claimed the lives of an estimated 100,000 Londoners.

“Despite the Great Plague killing on such a devastating scale, traces of it have eluded archaeologists for some time – because it was such a fast-acting disease it left no trace on the bones,” explained the Museum of London Archaeology, in a blog post.

The bacterium, which is no longer active, perished days after the infected individuals died.

However, a mass burial site discovered last year during construction at London’s Liverpool Street Station provided scientists with crucial clues. Experts took samples from the teeth of 20 people found at the New Churchyard site. The samples were sent for analysis at Germany’s Max Planck Institute and the plague pathogen Yersinia pestis was found in five of the 20 samples.

“The enamel shells of the teeth protected and preserved the DNA, essentially acting as little time capsules, providing scientific evidence that these people had been exposed to the bacterium,” said the Museum of London, in its blog post. “Other archaeological evidence, including pottery and coffin handles, point to the pit being in use in the mid-17th century, providing further evidence that it dates to the Great Plague.”

The Museum also noted that the survival of ancient DNA is low when buried for hundreds of years. “The fact that not all of the samples tested positive does not mean that these people did not die from the plague,” it said.

The construction at Liverpool Street Station is part of Crossrail, a major transport project in and around the U.K. capital.

“The Crossrail project has given archaeologists a rare opportunity to study previously inaccessible areas of London,” said Jay Carver, the Crossrail lead archaeologist, in a statement. “The discovery of the ancient DNA, which has eluded scientists for so long, is yet another piece of the jigsaw that we are piecing together to learn more about the lives and deaths of 16th to 18th Century Londoners.”

Scientists hope that their research will provide insight into the plague’s evolution and spread. Molecular pathologists are now working to sequence the pathogen’s full genome and hope to compare the 1665 Great Plague to the 1348 Black Death and modern outbreaks.

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