Scientists have mapped out the entire genetic map of theBlack Death, a 14th century bubonic plague that killed 50 million Europeans inone of the most devastating epidemics in history.
The work, which involved extracting and purifying DNA fromthe remains of Black death victims buried in London's "plague pits,"is the first time scientists have been able to draft a reconstructed genome ofany ancient pathogen.
Their result -- a full draft of the entire Black Deathgenome -- should allow researchers to track changes in the disease's evolutionand virulence, and lead to better understanding of modern-day infectiousdiseases.
Building on previous research which showed that a specificvariant of the Yersinia pestis (Y. pestis) bacterium was responsible for theplague that ravaged Europe between 1347 and 1351, a team of German, Canadianand American scientists went on to "capture" and sequence the entiregenome of the disease.
"The genomic data show that this bacterial strain, orvariant, is the ancestor of all modern plagues we have today worldwide. Everyoutbreak across the globe today stems from a descendant of the medievalplague," said Hendrik Poinar, of Canada's McMaster University, who workedwith the team.
"With a better understanding of the evolution of thisdeadly pathogen, we are entering a new era of research into infectiousdisease."
Major technical advances in DNA recovery and sequencing havedramatically expanded the scope of genetic analysis of ancient specimens,opening up new ways of trying to understand emerging and re-emerginginfections.
Experts say the direct descendants of the same bubonicplague still exist today, killing around 2,000 people a year.
A virulent strain of E. coli bacteria which caused a deadlyoutbreak of infections in Germany and France earlier this year was also foundto contain DNA sequences from plague bacteria.
For this study Poinar's team analysed skeletal remains fromBlack Death victims buried in London's East Smithfield "plague pits,"which are located under what is now the Royal Mint.
By focusing on promising specimens from the dental pulp offive bodies, which had already been pre-screened for the presence of Y. pestis,they were able to extract, purify and enrich the disease's DNA and at the sametime reduce the amount of background non-plague DNA which might interfere.
Linking the 1349 to 1350 dates of the skeletal remains tothe genetic data allowed the researchers to calculate the age of the ancestorof Y. pestis that caused the mediaeval plague.
Poinar, whose work was published in the journal Nature, saidthe team found that in 660 years of evolution, the genetic map of the ancientorganism had only barely changed. "The next step is to determine why thiswas so deadly," he said.
Johannes Krause Of Germany's University of Tubingen, whoalso worked on the study, said the same approach could now be used to study thegenomes of all sorts of historic pathogens.
"This will provide us with direct insights into theevolution of human pathogens and historical pandemics," he said in astatement.