We report the isolation and detailed characterization of the novel strain, Partizansk/2006, of Powassan virus (POWV) from a human case of infection, which occurred in Primorsky krai, Russia, in 2006. Comparative complete genome sequence analysis of the Far Eastern strains Spassk-9 (1975), Nadezdinsk-1991 and Partizansk/2006 of POWV revealed that these strains are 99.8% similar to the LB strain, which was isolated in Canada in 1958. Phylogenetic analysis of 5' UTR sequences of five other strains of POWV isolated from 1972 to 1986 in Primorsky krai produced similar results. Presumably, Far Eastern POWV has common putative ancestor with LB strain POWV from North America, and the time of divergence of these POWVs is relatively short. We conclude that POWV has become endemic in Far Eastern Russia.

BackgroundAmphipods (Crustacea) of Lake Baikal are a very numerous and diverse group of invertebrates generally believed to have originated by adaptive radiation. The evolutionary history and phylogenetic relationships in Baikalian amphipods still remain poorly understood. Sequencing of mitochondrial genomes is a relatively feasible way for obtaining a set of gene sequences suitable for robust phylogenetic inferences. The architecture of mitochondrial genomes also may provide additional information on the mechanisms of evolution of amphipods in Lake Baikal.ResultsThree complete and four nearly complete mitochondrial genomes of Baikalian amphipods were obtained by high-throughput sequencing using the Illumina platform. A phylogenetic inference based on the nucleotide sequences of all mitochondrial protein coding genes revealed the Baikalian species to be a monophyletic group relative to the nearest non-Baikalian species with a completely sequenced mitochondrial genome - Gammarus duebeni. The phylogeny of Baikalian amphipods also suggests that the shallow-water species Eulimnogammarus has likely evolved from a deep-water ancestor, however many other species have to be added to the analysis to test this hypothesis.The gene order in all mitochondrial genomes of studied Baikalian amphipods differs from the pancrustacean ground pattern. Mitochondrial genomes of four species possess 23 tRNA genes, and in three genomes the extra tRNA gene copies have likely undergone remolding. Widely varying lengths of putative control regions and other intergenic spacers are typical for the mitochondrial genomes of Baikalian amphipods.ConclusionsThe mitochondrial genomes of Baikalian amphipods display varying organization suggesting an intense rearrangement process during their evolution. Comparison of complete mitochondrial genomes is a potent approach for studying the amphipod evolution in Lake Baikal.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3357-z) contains supplementary material, which is available to authorized users.

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In this paper, we revealed the genetic structure and migration history of the Powassan virus (POWV) reconstructed based on 25 complete genomes available in NCBI and ViPR databases (accessed in June 2021). The usage of this data set allowed us to perform a more precise assessment of the evolutionary rate of this virus. In addition, we proposed a simple Bayesian technique for the evaluation and visualization of ‘temporal signal dynamics’ along the phylogenetic tree. We showed that the evolutionary rate value of POWV is 3.3 × 10−5 nucleotide substitution per site per year (95% HPD, 2.0 × 10−5–4.7 × 10−5), which is lower than values reported in the previous studies. Divergence of the most recent common ancestor (MRCA) of POWV into two independent genetic lineages most likely occurred in the period between 2600 and 6030 years ago. We assume that the divergence of the virus lineages happened due to the melting of glaciers about 12,000 years ago, which led to the disappearance of the Bering Land Bridge between Eurasia and North America (the modern Alaskan territory) and spatial division of the viral areal into two parts. Genomic data provide evidence of the virus migrations between two continents. The mean migration rate detected from the Far East of Russia to North America was one event per 1750 years. The migration to the opposite direction occurred approximately once per 475 years.

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In this study, we present a complete mitochondrial genome of a deep-water amphipoda Brachyuropus grewingkii (Dybowsky, 1874) from Lake Baikal. A circular mitochondrial DNA has 17,118 bp in length and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, a putative control region, and five intergenic spacers. An extended control region and altered positions of some tRNA genes distinguish mitochondrial genome of B. grewingkii from the mitochondrial genomes described for other Baikalian amphipoda species.