title: NGS population genetics analyses reveal divergent evolution of a Lyme Borreliosis agent in Europe and Asia.
abstract: Borrelia bavariensis is a recently described agent of Lyme disease within the B. burgdorferi sensu lato species complex and exhibits a strong capacity for human pathogenicity. B. bavariensis strains are widely distributed in Eurasia spanning the distribution range of the tick vectors Ixodes persulcatus and I. ricinus. It has been suggested that B. bavariensis forms two populations, one of which arose through vector adaptation and geographic expansion. We have performed phylogenetic and population genetic analyses with next-generation sequencing data of 26 strains of B. bavariensis targeting the main linear chromosome and two plasmids (lp54, cp26). A very low number of single nucleotide polymorphisms (SNPs) was found in the European population and a deep branching pattern between European and Asian B. bavariensis was observed in all phylogenies. The results confirm the population structure of B. bavariensis and strongly support the hypothesis of clonal expansion of the European population of B. bavariensis. In addition, signals of positive selection identified in the populations further support the hypothesis that the European population of B. bavariensis likely underwent vector adaptation in its recent evolutionary history. Identified genes represent promising candidates for experimental vector adaptation studies. Thus, this species forms a very good model to study vector adaptation, which is known to play an important role in the geographic distribution of B. burgdorferi. Analysis of well known virulence determinants that are attributed to severity of clinical manifestation in B. burgdorferi s.s. revealed no variation within the European population of B. bavariensis, underlining the importance of including various Borrelia species into investigations that aim to understand the pathogenesis of Lyme disease agents.
authors.affiliation: LMU Munich, Department Biology II, Großhaderner Str. 2, 82152 Munich, Germany. Electronic address: F.Gatzmann@gmail.com.
authors.forename: Fanny
authors.initials: F
authors.lastname: Gatzmann
authors.affiliation: LMU Munich, Department Biology II, Großhaderner Str. 2, 82152 Munich, Germany. Electronic address: metzler@bio.lmu.de.
authors.forename: Dirk
authors.initials: D
authors.lastname: Metzler
authors.affiliation: Gene Center Munich, Lafuga, LMU Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany. Electronic address: krebs-st@lmb.uni-muenchen.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Krebs
authors.affiliation: Gene Center Munich, Lafuga, LMU Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany. Electronic address: blum@lmb.uni-muenchen.de.
authors.forename: Helmut
authors.initials: H
authors.lastname: Blum
authors.affiliation: Bayerisches Landesamt für Gesundheits- und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany. Electronic address: andreas.sing@lgl.bayern.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Sing
authors.affiliation: Department of Veterinary Medicine, Joint Faculty of Veterinary Medicine, Yamaguchi University, Yamaguchi, Yamaguchi 753-8515, Japan; Department of Bacteriology-I, National Institute of Infectious Diseases, Tokyo 162-8640, Japan. Electronic address: a-takano@yamaguchi-u.ac.jp.
authors.forename: Ai
authors.initials: A
authors.lastname: Takano
authors.affiliation: Department of Bacteriology-I, National Institute of Infectious Diseases, Tokyo 162-8640, Japan; United Graduate School of Agricultural Science and Veterinary Science, Gifu University, Gifu, 501-1193, Japan. Electronic address: kbata@niid.go.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kawabata
authors.affiliation: Bayerisches Landesamt für Gesundheits- und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany. Electronic address: volker.fingerle@lgl.bayern.de.
authors.forename: Volker
authors.initials: V
authors.lastname: Fingerle
authors.affiliation: Bayerisches Landesamt für Gesundheits- und Lebensmittelsicherheit (LGL), Veterinärstraße 2, 85764 Oberschleißheim, Germany. Electronic address: gabriele.margos@lgl.bayern.de.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Margos
authors.affiliation: LMU Munich, Department Biology II, Großhaderner Str. 2, 82152 Munich, Germany. Electronic address: nbecker@biologie.uni-muenchen.de.
authors.forename: Noémie S
authors.initials: NS
authors.lastname: Becker
mesh_terms: D000818:Animals; D001096:Arachnid Vectors / Q000382:microbiology*; D001208:Asia / Q000453:epidemiology; D001898:Borrelia / Q000235:genetics* / Q000302:isolation & purification; D002876:Chromosomes, Bacterial / Q000235:genetics*; D005060:Europe / Q000453:epidemiology; D005828:Genetics, Population; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D018884:Ixodes / Q000382:microbiology*; D008193:Lyme Disease / Q000453:epidemiology / Q000382:microbiology*; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics*; D017422:Sequence Analysis, DNA
keywords: Borrelia bavariensis; Evolution; Ixodes persulcatus; Ixodes ricinus; Lyme disease; Population genetics