After a series of biochemical tests and evaluations to determine several unknown bacteria, the Yersinia pestis bacterium was chosen for reporting. The discovery of Y. pestis dates back to 1894 by the French-Swiss doctor and bacteriologist named Alexandre Yersin. The name Yersinia pestis is synonymous with its more common name, the plague. Y. pestis is known to infect small rodents such as mice and rats, but is transmitted to humans through the bite of an infected animal or flea. Although this bacterium is still known to cause disease today, it is infamous for three pandemics that occurred in previous centuries. According to the Centers for Disease Control and Prevention, the first recorded pandemic occurred in 541 AD and is known as Justinian's Plague. The second pandemic originated in China in 1334 and received the sensational name of “Black Death”. Finally, the third epidemic occurred in 1860 and is known as the Modern Plague. It was only at the end of the modern plague that scientists discovered the causative agent and mode of transmission of the Yersinia pestis bacterium. Yersinia pestis is a zoonosis classified in the Enterobacteriaceae family. These are gram-negative coccobacilli which do not form spores and which, when grown on agar, form white/translucent dot-like colonies. The distinctive qualities of the Y. pestis are its bipolar coloration, negative test results for lactose fermentation, urease and indole production, and positive tests for catalase. This pleomorphic bacterium is facultatively aerobic with an optimal growth temperature at 28 degrees Celsius. At temperatures above 37 degrees Celsius, it appears that Y. pestis is not motile, but at temperatures below 30 degrees Ce...... middle of paper ......uciana L. "Challenges for laboratory diagnosis of Yersinia Pestis in the Clinical Laboratory." Laboratory diagnosis of Y. Pestis. UPMC Center for Health Security, December 29, 2005. Web. April 07, 2014.Du, Yidong, Roland Rosqvist, and Ake Forsberg. “Role of Yersinia pestis fraction 1 antigen in the inhibition of phagocytosis.” Role of Yersinia Pestis fraction 1 antigen in the inhibition of phagocytosis. American Society for Microbiology, 5 December 2001. Web. 07 April 2014."Plague." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, June 13, 2012. Web. April 7, 2014."Plague." Treatment at the Mayo Clinic. Mayo Foundation for Medical Education and Research, nd Web. 07 April 2014."Yersinia Pestis - Plague - Discover Life." Yersinia Pestis - Plague - Discover life. The Global Invasive Species Database, 31 March 2006. Web. 07 April. 2014.