Rickettsia

Rickettsia is a genus of small, gram-negative, coccobacillary bacteria that are obligate parasites of eukaryotic cells. They are most commonly found in humans and other vertebrates, where they cause numerous diseases, such as typhus, rickettsialpox, Boutonneuse fever, Q fever, and Rocky Mountain spotted fever. Rickettsia can also be found in arthropods, such as fleas, ticks, and mites, from which they may be transmitted to humans. Many species are emerging, and some can be used to study various aspects of cellular and molecular biology, such as antibiotic and host resistance, virulence, and the role of reactive oxygen species in intracellular signaling.