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''Coxiella burnetii'' is an obligate intracellular bacterial pathogen, and is the causative agent of Q fever. The genus ''Coxiella'' is morphologically similar to ''Rickettsia'', but with a variety of genetic and physiological differences. ''C. burnetii'' is a small Gram-negative bacterium that is highly resistant to environmental stresses such as high temperature, osmotic pressure, and ultraviolet light. These characteristics are attributed to a small cell variant form of the organism that is part of a biphasic developmental cycle, including a more metabolically and replicatively active large cell variant form. It can survive standard disinfectants, and is resistant to many other environmental changes like those presented in the phagolysosome.〔 "In contrast to other rickettsiae, which are highly sensitive and easily killed by chemical disinfectants and changes in their surroundings, C. burnetii is highly resistant" & "The organisms are resistant to heat, drying, and many common disinfectants."〕 ==History and naming== Research in the 1920s and 1930s identified what appeared to be a new type of ''Rickettsia'', isolated from ticks, that was able to pass through filters. The first description of what may have been ''Coxiella burnetii'' was published in 1925 by Hideyo Noguchi, but since his samples did not survive, it remains unclear as to whether it was the same organism. The definitive descriptions were published in the late 1930s as part of research into the cause of Q fever, by Edward Holbrook Derrick and Macfarlane Burnet in Australia, and Herald Rea Cox and Gordon Davis at the Rocky Mountain Laboratory (RML) in the United States. The RML team proposed the name ''Rickettsia diaporica'', derived from the Greek word for having the ability to pass through filter pores, to avoid naming it after either Cox or Davis if indeed Noguchi's description had priority. Around the same time, Derrick proposed the name ''Rickettsia burnetii'', in recognition of Burnet's contribution in identifying the organism as a ''Rickettsia''. As it became clear that the species differed significantly from other ''Rickettsia'', it was first elevated to a subgenus named after Cox, ''Coxiella'', and then in 1948 to its own genus of that name, proposed by Cornelius B. Philip, another RML researcher.〔 ''Coxiella'' was difficult to study because it could not be reproduced outside a host. However, in 2009, scientists reported a technique allowing the bacteria to grow in an axenic culture and suggested the technique may be useful for study of other pathogens. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Coxiella burnetii」の詳細全文を読む スポンサード リンク
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