From the article:
“Rebuilding the genetic code of the bacterium from DNA fragments was not easy, say the scientists.
They removed teeth from skeletons found in an ancient graveyard in London located under what is now the Royal Mint.”
– Black Death genetic code ‘built’ (BBC News, Oct. 12, 2011):
The genetic code of the germ that caused the Black Death has been reconstructed by scientists for the first time.
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.