A 3-D illustration of the Yersinia pestis bacteria, which claimed at least a third of Europe's population between 1347 and 1351 AD. Credit: Shutterstock
Scientists have been investigating the DNA of the bacterium that caused the Black Death over 600 years ago.
The bacterium Yersinia pestis is responsible for the bubonic plague and has caused a number of high-mortality epidemics in human history. In 1347-1351 AD the plague caused an estimated 25 million deaths in Europe, in an event known as the Black Death.
Technological advances in DNA recovery and sequencing mean scientists can now sequence the genomes of ancient specimens. As a result of these advances, an international team of scientists has reconstructed a draft sequence of the Y. pestis genome using the DNA of some of the victims of the Black Death.
The results suggest that contemporary Y. pestis epidemics may have their origins in the medieval era. “Through enrichment by DNA capture coupled with targeted high throughput DNA sequencing, we have reconstructed a draft genome for what is arguably the most devastating human pathogen in history, and revealed that the medieval plague of the fourteenth century was probably responsible for its introduction and widespread distribution in human populations,” the authors reported in the study, published in Nature.
The DNA came from the skeletal remains of four individuals buried in the East Smithfield cemetery in London. This area was acquired in late 1348-early 1349 AD for interment of Black Death victims.
The scientists examined 46 teeth and 53 bones to determine whether there were any potential evolutionary changes. The analyses concluded that the Black Death was the main historical event responsible for the introduction of the current strains of Y. pestis and their worldwide dissemination.
“Comparisons against modern genomes reveal no unique derived positions in the medieval organism, indicating that the perceived increased virulence of the disease during the Black Death may not have been due to bacterial phenotype.”
A comparison of the historical DNA with the DNA from modern strains of Y. pestis also indicated that factors other than microbial genetics may have an important role in the emergence of current strains. These factors include the environment, susceptibility of the host and vector dynamics.
“Although no extant Y. pestis strain possesses the same genetic profile as our ancient organism, our data suggest that few changes in known virulence-associated genes have accrued in the organism’s 660 years of evolution as a human pathogen.”
