1. Yersinia pestis Gram-negative, non-motile
Non-spore-forming coccobacillus
Facultative anaerobe, unencapsulated
dsDNA genome size of ~ 4,380 ± 135 kb
Bipolar staining (looks like safety pin)
Causative agent of Black Plague
LD50 ranges from 1 to 108 depending on strain
Pathogenicity linked with plasmids pCD1, pPCP1, and pMT1 ‪
1-2 images
General description
(gram stain, DNA characteristics)
Virulence facotris (invasins, adhesins, spreading factors)
Antimicrobial resistance characteristics
Flea
Bipolar staining
Invasin, Ail, YadA, YadB, YadC, Pla, and pH 6 antigen belong to the most prominent and best-known Yersinia adhesins. They act at different times and stages of infection complementing each other by their ability to bind a variety of host molecules such as collagen, fibronectin, laminin, β1 integrins, and complement regulators. 
Outer cell membrane  
© 2013 Mikula, Kolodziejczyk and Goldman.
Credit: I. Miralda – F2013

2. Y. pestis life cycle & pathogenicity
Employs an enzootic cycle using the oriental rat flea (Xenopsylla cheopis) as a vector
Y. pestis prevents blood from entering flea’s stomach
Blood pools in esophagus and after mixing with bacteria is regurgitated into mammalian host during feeding
Bacteria can only survive when phagocytized by macrophages
Unique adhesins and integrins used to block production of proinflammatory cytokines
Proliferate within & travels to regional lymph nodes and colonizes other parts of body
3 Plague types, each attacks different systems with decreasing incubation time & mortality rate
Bubonic (lymphatic) 2-6 days
Pneumonic (respiratory) 1-7 days
Septicaemic (blood) 8 hours-2 days