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Rickettsia prowazekii

Rickettsia prowazekii is a species of gram-negative, alphaproteobacteria, obligate intracellular parasitic, aerobic bacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the main reservoir for R. prowazekii is the flying squirrel. R. prowazekii is often surrounded by a protein microcapsular layer and slime layer; the natural life cycle of the bacterium generally involves a vertebrate and an invertebrate host, usually an arthropod, typically the human body louse. A form of R. prowazekii that exists in the feces of arthropods remains stably infective for months. R. prowazekii also appears to be the closest free-living relative of mitochondria, based on genome sequencing.



Henrique da Rocha Lima, a Brazilian doctor, discovered this bacterium in 1916. He named it after his colleague Stanislaus von Prowazek, who had died from typhus in 1915. Both Prowazek and Rocha Lima had been infected with typhus while studying its causative agent in a prison hospital in Hamburg, Germany.[1] This bacteria lacks flagella and is aerobic.[citation needed] It is stained gram-negative.[citation needed]

Evolutionary history[edit]

The genome of R. prowazekii is reduced, being just 1Mb in size and encoding 834 proteins. For this reason, R. prowazekii has sometimes been regarded as a model for the bacterial ancestor of mitochondria.[2]


Vaccines against R. prowazekii were developed in the 1940s, and were highly effective in reducing typhus deaths among U.S. soldiers during World War II. Immunity following recovery from infection with, or by immunization against, R. prowazekii is lifelong in most cases. However, R. prowazekii can establish a latent infection, which can reactivate after years or decades (referred to as Brill-Zinsser disease). Treatment with tetracycline antibiotics is usually successful.


  1. ^ Henrique da Rocha Lima at Who Named It?
  2. ^ Kurland, Charles G.; Andersson, Siv G. E.; Zomorodipour, Alireza; Andersson, Jan O.; Sicheritz-Pontén, Thomas; Alsmark, U. Cecilia M.; Podowski, Raf M.; Näslund, A. Kristina et al. (1998). "The genome sequence of Rickettsia prowazekii and the origin of mitochondria". Nature 396 (6707): 133–40. doi:10.1038/24094. PMID 9823893. 



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