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).