Taking a bite out of the plague.

In the mid-14th century, the Black Death hit Europe, ultimately killing about 75 percent of its population over the next 100 years. From descriptions of the disease, researchers have concluded that the responsible agent was Yersinia pestis, the bacterium that causes what is now called bubonic plague. Although many historical epidemics have been pinned on the microbe, the evidence has always been circumstantial. Scientists have now probed the dental remains of victims whose disease resembled bubonic plague and died as far back as 408 years ago. They found DNA sequences belonging to the bacterium Y. pestis.

In the study, Didier Raoult of the Universite de la Mediteranee in Marseille, France, and his colleagues recently gathered skulls from two mass graves--one dug in 1590 and one in 1722--in which plague victims from nearby hospitals were buried. They removed unerupted teeth from jawbones and, carefully guarding against contamination, looked for genetic material in the preserved dental pulp, the soft tissue in a tooth's central cavity. While ancient teeth from people who died of nonplague causes had no signs of a gene specific to Y pestis, 6 of the 12 teeth from presumed plague victims did contain the DNA, Raoult's team reports in the Oct. 27 Proceedings of the National Academy of Sciences. The scientists suggest that examining ancient dental pulp for bacterial and viral DNA may help resolve the causes of other epidemics in history.