The researchers extracted DNA fragments of the ancient bacterium from the teeth of medieval corpses found in London.
They say the pathogen is the ancestor of all modern plagues.
The research, published in the journal Nature, suggests the 14th Century outbreak was also the first plague pandemic in history.
Humans have rarely encountered an enemy as devastating as the bacterium, Yersinia pestis. Between 1347 and 1351 it sparked the Black Death, an infection carried by fleas that spread rapidly across Europe killing around 50 million people.
Now scientists have uncovered some of the genetic secrets of the plague, thanks to DNA fragments drilled from the teeth of victims buried in a graveyard in London's East Smithfield.
Professor Johannes Krause from the University of Tubingen, Germany, was a member of the research team. He said all current strains circulating in the world are directly related to the medieval bacterium.
The plague
- The plague is one of the oldest identifiable diseases known to man
- Plague is spread from one rodent to another by fleas, and to humans either by the bite of infected fleas or when handling infected hosts
- Recent outbreaks have shown that plague may reappear in areas that have long been free of the disease
- Plague can be treated with antibiotics such as streptomycin and tetracycline
- Source: World Health Organization
"It turns out that this ancient Yersinia pestis strain is very close to the common ancestor of all modern strains that can infect humans," he said.
"It's the grandmother of all plague that's around today."
Previously researchers had assumed the Black Death was another in a long line of plague outbreaks dating back to ancient Greece and Rome.
The Justinian Plague that broke out in the 6th Century was estimated to have killed 100 million people. But the new research indicates that plagues like the Justinian weren't caused by the same agent as the medieval epidemic.
"It suggests they were either caused by a Yersinia pestis strain that is completely extinct and it didn't leave any descendants which are still around today or it was caused by a different pathogen that we have no information about yet," said Professor Krause.
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