An international team -- led by researchers at McMaster University and the University of Tubingen in Germany -- has sequenced the entire genome of the Black Death, one of the most devastating¹ epidemics² in human history. This marks the first time scientists have been able to draft a reconstructed genome of any ancient pathogen, which will allow researchers to track changes in the pathogen's evolution and virulence³（毒性） over time. This work -- currently published online in the journal Nature -- could lead to a better understanding of modern infectious diseases.

Geneticists Hendrik Poinar and Kirsten Bos of McMaster University and Johannes Krause and Verena Schuenemann of the University of Tubingen collaborated⁴ with Brian Golding and David Earn of McMaster University, Hernán A. Burbano and Matthias Meyer of the Max Planck Institute for Evolutionary⁵ Anthropology⁶ and Sharon DeWitte of the University of South Carolina, among others.

In a separate study published recently, the team described a novel methodological（方法的） approach to pull out tiny degraded DNA⁷ fragments of the causative agent of the Black Death, and showed that a specific variant⁸ of the Yersinia pestis bacterium⁹, was responsible for the plague（瘟疫，灾祸） that killed 50 million Europeans between 1347 and 1351.

After this success, the next major step was to attempt to "capture" and sequence the entire genome, explains Poinar, associate professor and director of the McMaster Ancient DNA Centre and an investigator¹⁰ with the Michael G. DeGroote Institute of Infectious Disease Research, also at McMaster University.

"The genomic data show that this bacterial¹¹ strain, or variant, is the ancestor of all modern plagues we have today worldwide. Every outbreak across the globe today stems from a descendant（后裔） of the medieval plague," he says. "With a better understanding of the evolution of this deadly pathogen, we are entering a new era of research into infectious disease."

"Using the same methodology, it should now be possible to study the genomes of all sorts of historic pathogens," adds Krause, one of the lead authors of the study. "This will provide us with direct insights into the evolution of human pathogens and historical pandemics（普遍的） ."

The direct descendants of the same bubonic plague（黑死病） continue to exist today, killing¹² some 2,000 people each year.

"We found that in 660 years of evolution as a human pathogen, there have been relatively¹³ few changes in the genome of the ancient organism, but those changes, however small, may or may not account for the noted¹⁴ increased virulence of the bug¹⁵ that ravaged¹⁶ Europe," says Poinar. "The next step is to determine why this was so deadly."