Until very recently it was thought that just one bacterium was to blame for causing Lyme disease in humans. But it turns out that a second, related bug can cause it too. In 2013, during routine testing of bacterial DNA floating around in the blood samples of people suspected of having Lyme disease, researchers at the Mayo Clinic in Rochester, Minn., realized they were looking at something different.  “We detected this result which was positive, but it was clearly different from what we would have expected for Borrelia burgdorferi, which at that time was the only known cause of Lyme disease in the U.S.,” says Dr. Bobbi Pritt, a microbiologist at the Mayo Clinic.  When they sequenced the genome of the bacterium, they realized it was different enough to be considered a new species. It’s been dubbed Borrelia mayonii, after the Mayo Clinic. [Read more…]