The mitochondrial genome of the ornate sheep tick, Dermacentor marginatus.

The ornate sheep tick, Dermacentor marginatus, is widespread in Europe. Its vector role of various zoonotic pathogens received much attention in these regions. However, the genomic resources of the ticks are limited. In this study, the complete mitochondrial genome of a single female D. marginatus collected in Slovakia was sequenced through the Illumina HiSeq sequencing platform. The mitochondrial genome is 15,067 bp long and contains 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes. The overall G+C content is 21.6%. The gene order is identical to that of Metastriata ticks. The codon usage pattern is similar with that of other tick species. As in other ticks, two truncated tRNA genes were observed. Two control regions were found between tRNA-Leu and tRNA-Cys, tRNA-Ile and rrnS, respectively. The mitochondrial genome contains three noncoding regions, which is similar to that in D. nitens. The noncoding region located between rrnS and tRNA-Val is shorter than that of other Dermacentor species. Phylogenetic analyses indicate that D. marginatus is clustered with other Dermacentor species. These findings are helpful for exploring the systematics and evolution of ticks in the future.

The bacterial microbiome of field-collected Dermacentor marginatus and Dermacentor reticulatus from Slovakia.

BACKGROUND: The important roles of microbial flora in tick biology and ecology have received much attention. Dermacentor marginatus and Dermacentor reticulatus are known vectors of various pathogens across Europe, including Slovakia. However, their bacterial microbiomes are poorly explored. METHODS: In this study, bacterial microbiomes of field-collected D. marginatus and D. reticulatus from Slovakia were characterized using 16S rRNA high-throughput sequencing. RESULTS: Different analyses demonstrated that the D. marginatus and D. reticulatus microbiomes differ in their diversity and taxonomic structures. Furthermore, species- and sex-specific bacteria were detected in the two species. A possible bacterial pathogen "Candidatus Rhabdochlamydia sp." was detected from D. marginatus males. Among the observed bacteria, Rickettsia showed high abundance in the two species. Several maternally inherited bacteria such as Coxiella, Arsenophonus, Spiroplasma, Francisella and Rickettsiella, were abundant, and their relative abundance varied depending on tick species and sex, suggesting their biological roles in the two species. CONCLUSIONS: The bacterial microbiomes of field-collected D. marginatus and D. reticulatus were shaped by tick phylogeny and sex. Maternally inherited bacteria were abundant in the two species. These findings are valuable for understanding tick-bacteria interactions, biology and vector competence of ticks.