Research into the history of the plague reveals ho...  ...mapping the history of mutations to the bacterium Yersinia pestis , which killed millions of people at a time during...  ...he acquisition of a single gene named pla gave Y. pestis the ability to cause pneumonia, causing a form of...  ...among the most in...

Photo: McMaster University Is...  ...Roman Empire. The plague, caused by the bacterium Yersinia pestis , made another appearance in Europe several centur...

Remember Black Death? You know, the medieval plague that swept across Europe and killed off about half of that continent's population? Well, it's back ... at least in genetic form thanks...