Wilder Hannah K, Raffel Sandra J, Barbour Alan G, Porcella Stephen F, Sturdevant Daniel E, Vaisvil Benjamin, Kapatral Vinayak, Schmitt Daniel P, Schwan Tom G, Lopez Job E
Department of Pediatrics, Section of Tropical Medicine, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas, United States of America.
Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America.
PLoS One. 2016 Feb 4;11(2):e0147707. doi: 10.1371/journal.pone.0147707. eCollection 2016.
Adaptation is key for survival as vector-borne pathogens transmit between the arthropod and vertebrate, and temperature change is an environmental signal inducing alterations in gene expression of tick-borne spirochetes. While plasmids are often associated with adaptation, complex genomes of relapsing fever spirochetes have hindered progress in understanding the mechanisms of vector colonization and transmission. We utilized recent advances in genome sequencing to generate the most complete version of the Borrelia turicatae 150 kb linear megaplasmid (lp150). Additionally, a transcriptional analysis of open reading frames (ORFs) in lp150 was conducted and identified regions that were up-regulated during in vitro cultivation at tick-like growth temperatures (22°C), relative to bacteria grown at 35°C and infected murine blood. Evaluation of the 3' end of lp150 identified a cluster of ORFs that code for putative surface lipoproteins. With a microbe's surface proteome serving important roles in pathogenesis, we confirmed the ORFs expression in vitro and in the tick compared to spirochetes infecting murine blood. Transcriptional evaluation of lp150 indicates the plasmid likely has essential roles in vector colonization and/or initiating mammalian infection. These results also provide a much needed transcriptional framework to delineate the molecular mechanisms utilized by relapsing fever spirochetes during their enzootic cycle.
适应是生存的关键，因为媒介传播的病原体在节肢动物和脊椎动物之间传播，而温度变化是一种环境信号，可诱导蜱传螺旋体基因表达的改变。虽然质粒通常与适应有关，但回归热螺旋体复杂的基因组阻碍了我们对媒介定殖和传播机制的理解。我们利用基因组测序的最新进展，生成了最完整版本的杜氏疏螺旋体150 kb线性大质粒（lp150）。此外，我们对lp150中的开放阅读框（ORF）进行了转录分析，并确定了在蜱类生长温度（22°C）下体外培养期间相对于在35°C下生长的细菌和感染鼠血上调的区域。对lp150 3'端的评估确定了一组编码假定表面脂蛋白的ORF。由于微生物的表面蛋白质组在发病机制中起重要作用，我们证实了与感染鼠血的螺旋体相比，这些ORF在体外和蜱体内的表达。lp150的转录评估表明，该质粒可能在媒介定殖和/或引发哺乳动物感染中起重要作用。这些结果还提供了一个急需的转录框架，以描绘回归热螺旋体在其动物疫源循环中利用的分子机制。
