Scientists claimed to have cracked the genetic DNA of the worst bubonic plague in Europe's history, the Black Death, for the first time after analyzing the teeth of more than 700 year-old skeletons.

The scientists found that a specific variant of the Yersinia pestis bacterium was responsible for the worst plague that killed 30 million to 50 million people in Europe between 1347 and 1351.

In order to reconstruct the 14th century bug, the Yersinia pestis genome, researchers extracted DNA from the teeth of skeletons exhumed from a cemetery in East Smithfield in London, a well-known medieval burial site for victims of the plague. The experts say the genome of the deadly bacterium, also known as a pathogen, is the ancestor of all modern plagues.

It turns out that this ancient Yersinia pestis strain is very close to the common ancestor of all modern strains that can infect humans, said Professor Johannes Krause from the University of Tubingen, Germany, who was a member of the research team. It's the grandmother of all plague that's around today.

The researchers said the study determined that the germ, which hasn't changed much over 700 years, is still circulating. But it didn't probably cause earlier plagues in Rome and Greece, suggesting that the European outbreak was the first to spread the bacteria worldwide.

The researchers were able to purify and enrich the pathogen's DNA from the dental pulp, which is the part in the center of a tooth made up of living connective tissue and cells called odontoblasts, and exclude material from human and fungal sources.

The researchers believe the techniques they developed in this work can be used to study the genomes of many other ancient pathogens. The research, published in the journal Nature, also suggests that the 14th Century outbreak was the first plague pandemic in history.

Every outbreak across the globe today stems from a descendant of the medieval plague, said Hendrik Poinar, lead scientist 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.

Poinar said that antibiotics like tetracycline could beat the plague bacteria and the bacteria didn't seem to have the properties that enabled other germs to become drug-resistant. Changes in the treatment of the sick, improved sanitation and economics and better immune system put humanity in a safer position now, he added.

These findings support the notion that factors other than microbial genetics, such as environment, vector dynamics and host susceptibility, should be at the forefront of epidemiological discussions regarding emerging Yersinia pestis infections, the researchers concluded.