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〕 ''Rickettsia asiatica''〔Fujita, H.; Fournier, P.-E., et al. (2006), ("''Rickettsia asiatica'' sp. nov., isolated in Japan" ), ''Int J Syst Evol Microbiol'' 56 (Pt 10): 2365–2368〕 ''Rickettsia australis''〔 ''Rickettsia canadensis''〔 ''Rickettsia conorii''〔 ''Rickettsia cooleyi'' ''Rickettsia felis''〔La Scola, B.; Meconi, S., et al. (2002), ("Emended description of ''Rickettsia felis'' (Bouyer ''et al''. 2001), a temperature-dependent cultured bacterium" ), ''Int J Syst Evol Microbiol'' 52 (Pt 6): 2035–2041〕 ''Rickettsia heilongjiangensis'' ''Rickettsia helvetica'' ''Rickettsia honei'' ''Rickettsia hulinii'' ''Rickettsia japonica'' ''Rickettsia massiliae'' ''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 present as cocci (0.1 μm in diameter), rods (1–4 μm long), or thread-like (10 μm long). Being obligate intracellular parasites, the ''Rickettsia'' survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells (typically endothelial cells). Because of this, ''Rickettsia'' cannot live in artificial nutrient environments and is grown either in tissue or embryo cultures (typically, chicken embryos are used). In the past, it was positioned somewhere between viruses and true bacteria. However, unlike ''Chlamydia'', ''Mycoplasma'', and ''Ureaplasma'', rickettsial organisms possess true cell walls similar to other Gram-negative bacteria.〔(【引用サイトリンク】url=http://www.hgsc.bcm.tmc.edu/microbial-detail.xsp?project_id=126 )〕 The majority of ''Rickettsia'' bacteria are susceptible to antibiotics of the tetracycline group. Despite the similar name, ''Rickettsia'' bacteria do not cause rickets, which is a result of vitamin D deficiency. Instead, they are named after Howard Taylor Ricketts. ''Rickettsia'' species are carried by many arthropods, including chiggers, ticks, fleas, and lice, and cause diseases in humans such as typhus, rickettsialpox, Boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever and Queensland tick typhus (Australian tick typhus). They have also been associated with a range of plant diseases. The name rickettsia is often used for any member of the Rickettsiales. They are one of closest living relatives to the bacteria that were the origin of the mitochondria organelles that exist inside most eukaryotic cells. The method of growing ''Rickettsia'' in chicken embryos was invented by Ernest William Goodpasture and his colleagues at Vanderbilt University in the early 1930s. ==Classification== The classification of ''Rickettsia'' into three groups (spotted fever, typhus, and scrub typhus) was based on serology. This grouping has since been confirmed by DNA sequencing. All three of these contain human pathogens. The scrub typhus group has been reclassified as a new genus – ''Orientia'' – but many medical textbooks still list this group under the rickettsial diseases. Rickettsia are more widespread than previously believed and are known to be associated with arthropods, leeches, and protists. Divisions have also been identified in the spotted fever group and this group likely should be divided into two clades.〔Gillespie J.J., Beeir M.S., Rahman M.S., Ammerman N.C., Shallom J.M., Purkayastha A., Sobral B.S., Azad A.F. Plasmids and rickettsial evolution: insight from 'Rickettsia felis'" ''PLoS ONE'' 2007;2:e266. .〕 Arthropod-inhabiting rickettsiae are generally associated with reproductive manipulation (such as parthenogenesis) to persist in host lineage In March 2010, Swedish researchers reported a case of bacterial meningitis in a woman caused by ''Rickettsia helvetica'' previously thought to be harmless.〔("Rickettsia helvetica in Patient with Meningitis, Sweden, 2006" ''Emerging Infectious Diseases'', Volume 16, Number 3 - March 2010 )〕 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「Rickettsia」の詳細全文を読む スポンサード リンク
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