背景:埃里希菌属由tick传播的强制性细胞内细菌组成,可引起具有医学和农业重要性的致命疾病。埃里希亚sp.HF,从日本的Ixodesovatus蜱中分离[也称为I.ovatusEhrlichia(IOE)试剂],在实验室小鼠中引起急性致命感染,类似于由恰菲埃里希菌引起的急性致命人类单核细胞埃里希菌病。由于没有小型实验动物模型来研究致命的人类埃里希体病,埃里希亚sp.HF提供了所需的疾病模型。然而,无法培养埃里希氏菌。HF和缺乏基因组信息一直是推进这种动物模型的障碍。此外,埃里希亚sp.HF在文献中有几个名称,因为它没有分类学上认可的名称。
结果:我们稳定培养了埃里希菌。来自HF株感染小鼠的犬组织细胞白血病DH82细胞中的HF,并确定了其完整的基因组序列。埃里希亚sp.HF具有1,148,904bp的单个双链环状染色体,它编码866种蛋白质,其代谢潜力与查菲大肠杆菌相似。埃里希亚sp.HF编码在查非芬大肠杆菌中鉴定的所有毒力因子的同源物,包括P28/OMP-1家族外膜蛋白的23个旁系同源物,IV型分泌系统装置和效应蛋白,双组分系统,锚蛋白重复蛋白,和串联重复蛋白。埃里希亚sp.HF是埃里希氏菌属中的一个新物种,通过与六种代表性埃里希菌属物种的全基因组比较证明,亚种,和菌株,使用平均核苷酸同一性,数字DNA-DNA杂交,和核心基因组比对序列同一性。
结论:埃里希菌的基因组。HF编码所有已知的毒力因子,将其证实为研究致命的人类埃里希菌病的模型。埃里希氏菌属之间的比较。HF和E.chaffeensis将能够鉴定与宿主特异性相关的体内毒力因子,疾病严重程度,和宿主炎症反应。我们建议将其命名为Ehrlichiasp。HF为日本埃里希氏菌。11月。(HF型应变),表示最初分离该细菌的地理区域。
BACKGROUND: The genus Ehrlichia consists of tick-borne obligatory intracellular bacteria that can cause deadly diseases of medical and agricultural importance. Ehrlichia sp. HF, isolated from Ixodes ovatus ticks in Japan [also referred to as I. ovatus Ehrlichia (IOE) agent], causes acute fatal infection in laboratory mice that resembles acute fatal human monocytic ehrlichiosis caused by Ehrlichia chaffeensis. As there is no small laboratory animal model to
study fatal human ehrlichiosis, Ehrlichia sp. HF provides a needed disease model. However, the inability to culture Ehrlichia sp. HF and the lack of genomic information have been a barrier to advance this animal model. In addition, Ehrlichia sp. HF has several designations in the literature as it lacks a taxonomically recognized name.
RESULTS: We stably cultured Ehrlichia sp. HF in canine histiocytic leukemia DH82 cells from the HF strain-infected mice, and determined its complete genome sequence. Ehrlichia sp. HF has a single double-stranded circular chromosome of 1,148,904 bp, which encodes 866 proteins with a similar metabolic potential as E. chaffeensis. Ehrlichia sp. HF encodes homologs of all virulence factors identified in E. chaffeensis, including 23 paralogs of P28/OMP-1 family outer membrane proteins, type IV secretion system apparatus and effector proteins, two-component systems, ankyrin-repeat proteins, and tandem repeat proteins. Ehrlichia sp. HF is a novel species in the genus Ehrlichia, as demonstrated through whole genome comparisons with six representative Ehrlichia species, subspecies, and strains, using average nucleotide identity, digital DNA-DNA hybridization, and core genome alignment sequence identity.
CONCLUSIONS: The genome of Ehrlichia sp. HF encodes all known virulence factors found in E. chaffeensis, substantiating it as a model Ehrlichia species to
study fatal human ehrlichiosis. Comparisons between Ehrlichia sp. HF and E. chaffeensis will enable identification of in vivo virulence factors that are related to host specificity, disease severity, and host inflammatory responses. We propose to name Ehrlichia sp. HF as Ehrlichia japonica sp. nov. (type strain HF), to denote the geographic region where this bacterium was initially isolated.