Y. pestis (Yersinia pestis) strand KIM belongs to biovar Mediaevalis. Y. pestis is actually catagorized into three subtypes or biovars; Antiqua, Medievalis, and Orientalis, each associated with a major pandemic and it is believed that Y. pestis is a clone that evolved from Y. pseudotuberculosis (Yersinia pseudotuberculosis) about 1.5 to 20 thousand years ago. Biovar Mediaevalis is thought to have descended from the bacteria that caused the second pandemic, the Black Death. The Black Death came in three forms, the bubonic, pneumonic, and septicemic. Each different form of plague killed people in a vicious way. All forms were caused by a bacterium called Y. pestis. This Coccobacillus is rod shaped, Gram-negative, and non-motile but has two distinct flagellar gene clusters; [...]