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Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long).
Within the Rickettsia species, these bacteria are divided into four clades. The clades include the ancestral group, spotted fever group (SFG), typhus group, and transitional group, and the determining factors for classifying into each group depends on phenotypic characteristics, phylogenetic organization, or the type of vector host they inhabit.
They are obligate intracellular parasites, and some are notable pathogens, including Rickettsia, which causes a variety of diseases in humans, and Ehrlichia, which causes diseases in livestock. Another genus of well-known Rickettsiales is the Wolbachia , which infect about two-thirds of all arthropods and nearly all filarial nematodes. [ 2 ]
Rickettsia rickettsii (red dots) in the cell of a deer tick Scientific classification; Domain: Bacteria: Phylum: Pseudomonadota: Class: Alphaproteobacteria: Order: Rickettsiales: Family: Rickettsiaceae Pinkerton 1936 (Approved Lists 1980) Tribes and genera "Candidatus Arcanobacter" Martijn et al. 2015 "Candidatus Cryptoprodota" corrig ...
Rickettsialpox - caused by Rickettsia akari, this disease is transmitted by mite bites and is generally milder than other rickettsial infections. Rocky Mountain spotted fever - caused by Rickettsia rickettsii , this disease is transmitted by tick bites and is prevalent in the Americas.
Rickettsia prowazekii is a species of gram-negative, obligate intracellular parasitic, aerobic bacilliform bacteria of class Alphaproteobacteria 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.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. [1] It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii . [ 2 ] R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus ( R. prowazekii ). [ 3 ]
Neorickettsia Scientific classification Domain: Bacteria Phylum: Pseudomonadota Class: Alphaproteobacteria Order: Rickettsiales Family: Ehrlichiaceae Genus: Neorickettsia Philip et al. 1953 (Approved Lists 1980) Species See text. Neorickettsia is a genus of bacteria. Species or strains in this genus are coccoid or pleomorphic cells that reside in cytoplasmic vacuoles within monocytes and ...