First time accepted submitter Quince alPillan writes "The bacteria behind the Black Death has a very unusual history. Its ancestor is an unassuming soil bacterium and the current strains of Yersinia pestis still infects thousands of people annually, but no longer causes the suite of horrifying symptoms associated with the medieval plagues. The radical differences, in fact, had led some to suggest that we had been blaming the wrong bacteria. Now, researchers have obtained DNA from some of London's plague victims, and confirmed that Y. pestis appears to be to blame. But the sequences also suggest that the strains of bacteria we see today may be different from the ones that rampaged through Europe."