Answer:
Plague is caused by Yersinia pestis. It is unicellular and placed in the bacteria domain.
Step-by-step explanation:
Plague is caused by bacteria Yersinia pestis , a zoonotic bacteria usually found in the small mammals and their fleas. It is a gram-negative, nonmotile, rod-shaped, coccobacillus bacteria, with no spores. It is a facultative anaerobic organism that can infect humans via the Oriental rat flea.Y. pestis was discovered in 1894 by Alexandre Yersin, a Swiss/French physician and bacteriologist from the Pasteur Institute, during an epidemic of the plague in Hong Kong. Yersin was a member of the Pasteur school of thought. Kitasato Shibasaburō, a German-trained Japanese bacteriologist who practised Koch's methodology, was also engaged at the time in finding the causative agent of the plague. However, Yersin actually linked plague with Y. pestis. named Pasteurella pestis in the past, the organism was renamed Yersinia pestis in 1944.