Rickettsias

Rickettsia

Rickettsia rickettsii (red dots) in the cell of a deer tick
Scientific classification
Domain:	Bacteria
Phylum:	Proteobacteria
Class:	Alphaproteobacteria
Subclass:	Rickettsidae
Order:	Rickettsiales
Family:	Rickettsiaceae
Genus:	Rickettsia da Rocha-Lima, 1916
Species
Rickettsea aeschlimannii Rickettsiae africae Rickettsea akari Rickettsia asiatica Rickettsia australis Rickettsia canadensis Rickettsia conorii Rickettsia cooleyi Rickettsia felis Rickettsia heilongjiangensis Rickettsia helvetica Rickettsia honei Rickettsia hulinii Rickettsia japonica Rickettsia massiliae Rickettsia monacensis Rickettsia montanensis Rickettsia parkeri Rickettsia peacockii Rickettsia prowazekii Rickettsia rhipicephali Rickettsia rickettsii Rickettsia sibirica Rickettsia slovaca Rickettsia tamurae Rickettsia typhi etc.

Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that can be present as cocci (0.1 μm in diameter), rods (1–4 μm long), or thread-like (10 μm long). The term rickettsia, named after Howard Taylor Ricketts, is often used interchangeably for any member of the Rickettsiales. Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells).Rickettsia cannot live in artificial nutrient environments and is grown either in tissue or embryo cultures; typically, chicken embryos are used: a method developed by Ernest William Goodpasture and his colleagues at Vanderbilt University in the early 1930s.