Researchers reconstruct full DNA of Black Death microbe

From the teeth of victims of the Black Death epidemic that struck in the fourteenth century, researchers have reconstructed the full DNA of the microbe that eliminated between one-third and one-half the population of Western Europe.

The plague bacterium, Yersinia pestis, is still highly virulent today but has different symptoms, which has led some historians to doubt whether it really was the agent of the Black Death.

Those doubts were put to rest last year with the detection of the bacterium's DNA in plague victims from mass graves across Europe. With the full genome now with them, the researchers hope to recreate the microbe itself to shed light on what made the Black Death outbreak so deadly.

The evidence so far points to the conditions of the time rather than properties of the bacterium itself. The genome recovered from the victims from the mass graves in East Smithfield in UK, bears a remarkable similarity to that of the present-day bacterium, according to the research team, led by Kirsten I Bos of McMaster University in Ontario and Johannes Krause of the University of Tübingen in Germany (See: Researchers reconstruct genome of the Black Death).

This is the first instance of the reconstruction of the genome of an ancient pathogen which could lead to  the tracking other ancient epidemics and how their microbes adapted to human hosts

The bacterium's genome is made up of a single chromosome, about 4.6 million DNA units long, and has three small rings of DNA called plasmids. In the 660 years following the Black Death epidemic, only 97 of these DNA units had changed and only a dozen of these changes occurred in genes and therefore would affect the organism's physical properties, according to the researchers report in yesterday's issue of the journal Nature.