title: Intron sequences from the CCT7 gene exhibit diverse evolutionary histories among the four lineages within the Babesia microti-group, a genetically related species complex that includes human pathogens.
abstract: Babesia microti, the primary causal agent of human babesiosis in North America, was thought to distribute in Europe in association with ixodid ticks and rodents. Recent analyses of β-tubulin and the eta subunit of the chaperonin-containing t-complex protein 1 (CCT7) genes revealed discrete clusters (a species-complex comprised of at least 4 taxa for the U.S., Kobe, Munich, and Hobetsu). To further assess the micro-evolutionary history and genetic variability within the taxon, we combined a set of 6 introns from the CCT7 gene to use as a rapidly evolving DNA marker. Phylogenetic and comparative sequence analyses subdivided the U.S. taxon into 3 geographic subclades--North America, western to central Eurasia, and northeastern Eurasia (≥ 98% bootstrap supports for each node). The Kobe taxon, which occurs only in a few geographic foci of Japan, could further be subdivided into 2 subgroups (100% support). The Munich and Hobetsu taxa, common to Europe and Japan, respectively, exhibited little or no pairwise sequence divergence among geographically diverse samples, suggesting an extreme population bottleneck during recent history. Despite the small sample size, this study provides a better understanding of the micro-evolutionary relationships and the genetic variability present within each lineage of the B. microti-group.
authors.affiliation: Laboratory Animal Science, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu 069-8501, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Fujisawa
authors.forename: Rui
authors.initials: R
authors.lastname: Nakajima
authors.forename: Michio
authors.initials: M
authors.lastname: Jinnai
authors.forename: Haruyuki
authors.initials: H
authors.lastname: Hirata
authors.forename: Aya
authors.initials: A
authors.lastname: Zamoto-Niikura
authors.forename: Takako
authors.initials: T
authors.lastname: Kawabuchi-Kurata
authors.forename: Satoru
authors.initials: S
authors.lastname: Arai
authors.forename: Chiaki
authors.initials: C
authors.lastname: Ishihara
mesh_terms: D000818:Animals; D041001:Babesia microti / Q000235:genetics*; D056404:Chaperonin Containing TCP-1 / Q000235:genetics*; D016000:Cluster Analysis; D019143:Evolution, Molecular; D006801:Humans; D007438:Introns; D058974:Phylogeography; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D056404:Chaperonin Containing TCP-1