Frutos R, Federici B A, Revet B, Bergoin M
BIOTROP-IGEPAM, CIRAD, Montpellier, France.
J Invertebr Pathol. 1994 May;63(3):294-300. doi: 10.1006/jipa.1994.1054.
Invertebrate pathogens of the genus Rickettsiella (Order Rickettsiales) undergo a developmental cycle more characteristic of chlamydial organisms (Order Chlamydiales) than of typical rickettsiae. Moreover, among recognized species of Rickettsiella, there is considerable variation in host range and in the ultrastructure and development of the infectious stage, i.e., the elementary body. To begin an analysis of the taxonomic relationships of the invertebrate pathogens belonging to the genus Rickettsiella and of the relationship of these to chlamydiae and other rickettsiae, genomic DNA of representative species was compared with respect to restriction enzyme site polymorphism, DNA-DNA hybridization, G + C ratios, and fine melting profiles. The strains studied included isolates currently classified as Rickettsiella grylli, R. popilliae, R. chironomi, Chlamydia psittaci, C. trachomatis, Coxiella burnetii, and Rickettsia conorii. Reciprocal DNA hybridization studies carried out under high-stringency conditions (65 degrees C) showed homology between R. grylli and R. popilliae isolates but not with the others, including two isolates of R. chironomi from the midge, Chironomus dorsalis, and the scorpion, Buthus occitanus. The R. chironomi isolates shared no detectable homology with each other or with any of the other strains or species. Additionally, no homology was detected between any of the Rickettsiella isolates and the species of Coxiella, Rickettsia, or Chlamydia. Results obtained from the DNA fine melting profiles and G + C ratios corresponded with the results obtained from the DNA hybridization studies. Thus, the present study indicates that, despite similarities in developmental cycles, Rickettsiella and Chlamydia are taxonomically distinct groups appropriately placed in different orders.(ABSTRACT TRUNCATED AT 250 WORDS)
立克次氏体属（立克次氏体目）的无脊椎动物病原体经历的发育周期，更具有衣原体生物（衣原体目）的特征，而非典型立克次氏体的特征。此外，在已确认的立克次氏体物种中，宿主范围以及感染阶段（即原体）的超微结构和发育存在相当大的差异。为了开始分析属于立克次氏体属的无脊椎动物病原体的分类关系，以及它们与衣原体和其他立克次氏体的关系，对代表性物种的基因组DNA进行了限制性酶切位点多态性、DNA-DNA杂交、G + C比例和精细解链曲线的比较。所研究的菌株包括目前分类为蟋蟀立克次氏体、绿僵菌立克次氏体、摇蚊立克次氏体、鹦鹉热衣原体、沙眼衣原体、贝氏考克斯氏体和康氏立克次氏体的分离株。在高严谨条件（65摄氏度）下进行的双向DNA杂交研究表明，蟋蟀立克次氏体和绿僵菌立克次氏体分离株之间存在同源性，但与其他菌株，包括来自摇蚊（背摇蚊）和蝎子（奥氏毒蝎）的两株摇蚊立克次氏体分离株没有同源性。摇蚊立克次氏体分离株彼此之间或与任何其他菌株或物种均未检测到同源性。此外，在任何立克次氏体分离株与考克斯氏体、立克次氏体或衣原体的物种之间均未检测到同源性。从DNA精细解链曲线和G + C比例获得的结果与DNA杂交研究获得的结果一致。因此，本研究表明，尽管发育周期相似，但立克次氏体和衣原体在分类学上是不同的群体，应归入不同的目。（摘要截短于250字）
