Yersinia pestis

Yersinia pestis is a species of gram-negative coccobacillus (i.e. rod-shaped bacterium) in the family Enterobacteriaceae, genus Yersinia; it is the infectious agent of bubonic plague. This organism can also cause pneumonic plague and septicemic plague. It was discovered simultaneously by Shibasaburo Kitasato and Alexandre Yersin in 1894.

The bacillus was originally called Pasteurella pestis, and was renamed after Alexandre Yersin.

see also Great Plague