Which of the following bacteria causes plague?

Correct option is D

The bacterium Yersinia pestis is the causative agent of the plague. It is primarily transmitted to humans through the bite of an infected flea. Plague can cause severe symptoms, including fever, chills, and swollen lymph nodes (buboes), and historically has led to pandemics.
Explanation of each option:
· (a) Escherichia coli – Incorrect. While Escherichia coli (E. coli) is a common bacterium that can cause foodborne illness, it is not the cause of plague.
· (b) Salmonella typhi – Incorrect. Salmonella typhi causes typhoid fever, not plague. It is transmitted through contaminated food or water.
· (c) Pseudomonas aeruginosa – Incorrect. Pseudomonas aeruginosa is an opportunistic pathogen that can cause infections, particularly in immunocompromised individuals, but it does not cause plague.
· (d) Yersinia pestis – Correct. Yersinia pestis is the bacterium responsible for causing plague, particularly during historical pandemics such as the Black Death.