Scientists reconstructed the genome of eight strains of the bacterium Y. pestis.
The plague is a mysterious disease. More than 1,000 years after its first appearance, the scientific community is still trying to understand how it appeared and how it developed. A group of German researchers recently succeeded in reconstructing the genome of eight strains of plague. This discovery allowed them to better understand its evolution. The findings were published in Proceedings of the National Academy of Sciences.
100 million deaths in five years
The research team focused on the first plague epidemic in history: the plague of Justinian. It struck the Mediterranean basin from 541 to around 750. During the first five years, it claimed almost 100 million lives.
A bacterium is at the origin of the disease: Yersinia pestis. To understand how it developed and what are the links between its different strains, scientists analyzed the remains of 21 people who died of the plague in different European countries: Austria, England, France, Germany and Spain. The genomes of eight strains of the disease have been reconstructed.
A major historical discovery
For the first time, researchers were able to genetically demonstrate the presence of the plague in England. In a cemetery in the county of Cambridgeshire, in the east of the country, 149 vaults from this period were analysed: residues of Y. pestis were found in 4 of them. “Probably almost all, if not all of England was ravaged, says Craig Cessford of the Cambridge Archeology Department. This discovery therefore represents a major historical event, (…) it means that the history of the beginning of Anglo-Saxon England must be rewritten.”
The scientists also discovered that there were many strains of the plague at this time: some were present in the same areas and others were genetically very close. Some of the strains of the bacterium have even had convergent evolution over the years. “The fact that all these genomes are from the same line indicates that the plague persisted in Europe and in the Mediterranean basin over this period, explains Marcel Keller, co-author of this research. These were not successive reintroductions of the bacterium.”
While knowledge of the disease is progressing, the work of researchers is far from over. The international scientific community is still trying to understand the origins of the plague before its first appearance in Egypt in 541.
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