Anstead Clare A, Chilton Neil B
Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Appl Environ Microbiol. 2013 Dec;79(24):7583-9. doi: 10.1128/AEM.02286-13. Epub 2013 Sep 27.
The genomic DNA of ixodid ticks from western Canada was tested by PCR for the presence of Rickettsia. No rickettsiae were detected in Ixodes sculptus, whereas 18% of the I. angustus and 42% of the Dermacentor andersoni organisms examined were PCR positive for Rickettsia. The rickettsiae from each tick species were characterized genetically using multiple genes. Rickettsiae within the D. andersoni organisms had sequences at four genes that matched those of R. peacockii. In contrast, the Rickettsia present within the larvae, nymphs, and adults of I. angustus had novel DNA sequences at four of the genes characterized compared to the sequences available from GenBank for all recognized species of Rickettsia and all other putative species within the genus. Phylogenetic analyses of the sequence data revealed that the rickettsiae in I. angustus do not belong to the spotted fever, transitional, or typhus groups of rickettsiae but are most closely related to "Candidatus Rickettsia kingi" and belong to a clade that also includes R. canadensis, "Candidatus Rickettsia tarasevichiae," and "Candidatus Rickettsia monteiroi."
通过聚合酶链反应（PCR）检测了加拿大西部硬蜱的基因组DNA中是否存在立克次氏体。在雕刻硬蜱中未检测到立克次氏体，而在所检测的奥氏硬蜱中有18%、安氏革蜱中有42%的生物体对立克次氏体的PCR检测呈阳性。利用多个基因对来自每个蜱种的立克次氏体进行了基因特征分析。安氏革蜱生物体中的立克次氏体在四个基因上的序列与孔雀立克次氏体的序列相匹配。相比之下，与GenBank中所有已识别的立克次氏体物种以及该属内所有其他假定物种的序列相比，奥氏硬蜱幼虫、若虫和成虫体内存在的立克次氏体在四个特征基因上具有新的DNA序列。对序列数据的系统发育分析表明，奥氏硬蜱中的立克次氏体不属于斑点热、过渡型或斑疹伤寒组立克次氏体，而是与“暂定立克次氏体金氏种”关系最为密切，属于一个进化枝，该进化枝还包括加拿大立克次氏体、“暂定立克次氏体塔拉谢维奇种”和“暂定立克次氏体蒙泰罗种”。
