The Vector and Water-Borne Pathogen Research Group, The School of Veterinary and Life Sciences, Murdoch University, Perth 6150, Australia; Present address: Australian National Insect Collection, CSIRO, Black Mountain, Canberra 2601, Australia.
German National Reference Centre for Borrelia, Bavarian Health and Food Safety Authority, Veterinärstr. 2, Oberschleissheim, 85764, Germany.
Infect Genet Evol. 2018 Dec;66:72-81. doi: 10.1016/j.meegid.2018.09.013. Epub 2018 Sep 18.
Borrelia are tick-borne bacteria that in humans are the aetiological agents of Lyme disease and relapsing fever. Here we present the first genomes of B. turcica and B. tachyglossi, members of a recently described and rapidly expanding Borrelia clade associated with reptile (B. turcica) or echidna (B. tachyglossi) hosts, transmitted by hard ticks, and of unknown pathogenicity. Borrelia tachyglossi and B. turcica genomes are similar to those of relapsing fever Borrelia species, containing a linear ~ 900 kb chromosome, a single long (> 70 kb) linear plasmid, and numerous short (< 40 kb) linear and circular plasmids, as well as a suite of housekeeping and macronutrient biosynthesis genes which are not found in Lyme disease Borrelia. Additionally, both B. tachyglossi and B. turcica contain paralogous vsp and vlp proteins homologous to those used in the multiphasic antigen-switching system used by relapsing fever Borrelia to evade vertebrate immune responses, although their number was greatly reduced compared to human-infectious species. However, B. tachyglossi and B. turcica chromosomes also contain numerous genes orthologous to Lyme disease Borrelia-specific genes, demonstrating a unique evolutionary, and potentially phenotypic link between these groups. Borrelia tachyglossi and B. turcica genomes also have unique genetic features, including degraded and deleted tRNA modification genes, and an expanded range of macronutrient salvage and biosynthesis genes compared to relapsing fever and Lyme disease Borrelia. These genomes and genomic comparisons provide an insight into the biology and evolutionary origin of these Borrelia, and provide a valuable resource for future work.
伯氏疏螺旋体是蜱传细菌，在人类中是莱姆病和回归热的病原体。在这里，我们首次呈现了土耳其包柔螺旋体和塔氏疏螺旋体的基因组，这两种螺旋体属于最近描述的、迅速扩张的伯氏疏螺旋体进化枝，与爬行动物（土耳其包柔螺旋体）或针鼹（塔氏疏螺旋体）宿主有关，由硬蜱传播，且其致病性未知。塔氏疏螺旋体和土耳其包柔螺旋体的基因组与回归热螺旋体物种的基因组相似，含有一条线性约 900kb 的染色体、一条单一的长 (>70kb) 线性质粒和许多短 (<40kb) 线性和环状质粒，以及一套管家基因和宏量营养素生物合成基因，这些基因在莱姆病螺旋体中不存在。此外，塔氏疏螺旋体和土耳其包柔螺旋体都含有与回归热螺旋体中用于多相抗原转换系统的 vsp 和 vlp 蛋白同源的 paralogous vsp 和 vlp 蛋白，尽管与感染人类的物种相比，它们的数量大大减少。然而，塔氏疏螺旋体和土耳其包柔螺旋体的染色体还含有许多与莱姆病螺旋体特异性基因同源的基因，这表明这些群体之间存在独特的进化和潜在的表型联系。塔氏疏螺旋体和土耳其包柔螺旋体的基因组还具有独特的遗传特征，包括降解和缺失的 tRNA 修饰基因，以及与回归热和莱姆病螺旋体相比，更多的宏量营养素回收和生物合成基因。这些基因组和基因组比较为我们深入了解这些螺旋体的生物学和进化起源提供了线索，并为未来的研究提供了有价值的资源。
