Figure 1. Schematic overview of the transmission cycles ofB. afzelii , B. bavariensis , and B. garinii across Eurasia. These three Borrelia genospecies are maintained predominately by the tick vector I. ricinus in Europe andI. persulcatus in Asia in a transmission cycle utilizing either rodents (B. afzelii and B. bavariensis ) or birds (B. garinii ) as reservoir hosts (Kurtenbach et al., 2006; Gabriele Margos et al., 2019, 2011). Borrelia garinii specifically utilizes interconnected terrestrial and marine based transmission cycles (P Comstedt et al., 2006; Pär Comstedt et al., 2009, 2011). In marine systems, this species is maintained by seabird reservoir host species and the vector I. uriae (Pär Comstedt et al., 2011). In both Europe and Asia, all three genospecies can be transmitted to humans through I. ricinus or I. persulcatus and can manifest as Lyme disease (Kurtenbach et al., 2006; Stanek et al., 2011).
Figure 2. Phylogeny of B. afzelii , B. bavariensis , and B. garinii based on the main chromosome corrected for recombining regions (see Suppl. Met.). The phylogeny was reconstructed with MrBayes v. 3.2.6 (Huelsenbeck & Ronquist, 2001; Ronquist et al., 2012) with ploidy set to haploid and a GTR (Tavaré, 1986) substitution model with gamma distributed rate variation. Three independent runs were launched and ran for 5 million generations each at which point convergence of parameters was checked with Tracer v. 1.7.1 (Rambaut et al., 2018). Consensus trees were built using the sumtcommand from MrBayes using a respective burn-in of 25%. The collapsed tree displays the full phylogeny (where monophyletic groups are collapsed if all isolates come from the same geographic origin) and then the expanded tree is shown independently for B. afzelii (A),B. bavariensis (B), and B. garinii (C). Colors correspond to geographic origin of the isolates: Europe (blue), Japan (red), purple (Russia), orange (China). For Japanese tick isolates, the island of origin is shown either as a diamond (Hokkaido) or star (Honshu) when known. The scale bar is in substitutions per site.
Figure 3. Analysis of plasmid content for sequenced strains estimated by the unique number of plasmid partitioning genes (PFam32, 49, 50, and 57.62) present in the assembled contigs. A plasmid was considered present if at least one of the partitioning genes was present. A) Boxplot of all plasmids present in isolates from Asia or Europe. The black circles represent the absolute number of unique plasmid types found in the geographic population defined as the plasmid type being observed in at least one isolate. P-values refer to an unpaired, two-sided t-test run on plasmid number between the European and Asian populations of each species individually. B) MDS analysis on plasmid presence/absence matrix for all samples. This figure shows the same MDS twice with emphasis on Asia (left) and Europe (right) by outlining isolates from Asia or Europe in a dark grey. Shapes correspond to genospecies: B. afzelii (square), B. bavariensis(circle), B. garinii (triangle).