Scientists reconstruct 700-year-old DNA of bug that caused Black Death

Scientists used the degraded strands to reconstruct the entire genetic code of the deadly bacterium.

It is the first time that experts have succeeded in drafting the genome of an ancient pathogen, or disease-causing agent.

The researchers found that a specific strain of the plague bug Yersinia pestis caused the pandemic that killed 30 million Europeans – between 30 per cent and 50 per cent of the total population – in just five years between 1347 and 1351. No bug or virus has wiped out a greater proportion of humankind in a single epidemic than the Black Death which was brought to Europe from China

The research indicates that Black Death was particularly deadly because Europeans had not evolved resistance to it and not because it was a special mutation. In fact, the strain is the “mother” of all modern bubonic plague bacteria and has hardly altered since then.

“Every outbreak across the globe today stems from a descendant of the medieval plague,” said lead scientist Dr Hendrik Poinar, from McMaster University in Canada.

“With a better understanding of the evolution of this deadly pathogen, we are entering a new era of research into infectious disease.”

Bubonic plague continues to kill some 2,000 people every year.

The scientists analysed the skeletal remains of four individuals exhumed from an East Smithfield “plague pit” sited under what is now the Royal Mint in London.

Tiny scraps of Yersinia pestis DNA were obtained from the victims’ dental pulp.

From these fragments, the researchers were able to reconstruct virtually the whole of the bug’s genetic code, or genome. The research, published in the journal Nature, shows that few genetic changes have taken place in the bacterium over the past 660 years.

The same techniques could now be used to study the genomes of other ancient pathogens.

“This will provide us with direct insights into the evolution of human pathogens and historical pandemics,” said co-author Dr Johannes Krause, from the University of Tubingen in Germany.

Plague pandemics that pre-dated the Black Death were probably caused by a very different Yersinia strain, or another type of bacteria altogether, the findings suggest.

One, the Justinian plague, spread across the eastern Roman empire in the 6th century.