EcoAlert: Black Death Source Identified from Medieval Bones

Blackdeath "This technology will open up a brave new world of ancient pathogen identification."

Hendrik Poinar at McMaster University

Some researchers have suggested that the Black Death, which wiped out about a third of Europe's population in the 14th century, was caused by a virus such as Ebola, but an analysis of DNA from a London plague pit concluded that the "plague" bacterium  was Yersinia pestis.

Hendrik Poinar at McMaster University and colleagues developed a technique to look for Yersinia DNA in the bones of Black Death victims. The task was made tricky because of the possibility of contamination, Poinar says. "When we extract DNA from the skeletons, we also get DNA from their environment."

To pick out the signature of Y. pestis, Poinar's team selected DNA from a modern strain and made a molecular "probe" that would bind to DNA from this type of bacterium. The team attached a magnetic chip to the probe and tested it on around 100 samples of teeth and bone excavated from a London plague pit.

The team used a magnet to fish out the chips, which carried bacterial DNA belonging to a strain of Y. pestis unlike any known today. The DNA was not present in teeth from skeletons buried elsewhere in London before the Black Death.

The findings are the first confirmation that these Black Death victims were infected with Y. pestis, said Poinar. The evidence was strong enough to convince two team members who had previously argued that the bug was not the cause.

Both Gilbert and Poinar reckon the technique could uncover the full genetic sequence of the bacterial strain behind the Black Death, which could help explain both why it was so virulent and how it evolved – as well as whether similarly devastating strains might appear in future.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1105107108


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