title: Revisiting Wolbachia supergroup typing based on WSP: spurious lineages and discordance with MLST.
abstract: The obligate intracellular bacteria Wolbachia are taxonomically subdivided into eight supergroups (named A-H). Supergroup typing of strains has been mostly based on phylogenetic inference of the Wolbachia surface protein (wsp), a gene that recently has been shown to experience high rates of recombination. This brings into question its suitability not only for microtaxonomy, but also for supergroup classification of the genus. A Multilocus Sequence Typing (MLST) scheme for Wolbachia has recently been developed that types strains based on five conserved genes, thus providing a rigorous supergroup annotation of strains. Here we report striking discrepancies in supergroup designation between MLST and wsp inferences, and propose a revision of current methods for Wolbachia supergroup typing. Transfer of whole wsp gene sequences between supergroups A and B has occurred. Furthermore, as a result of intragenic recombination, wsp phylogeny creates spurious basal lineages that are not supported by MLST. For example, the proposed supergroup G, based upon wsp alone, likely represents only a wsp recombinant clade. Removal of supergroup G is advised until and unless the existence of this lineage is substantiated by other sequence information (e.g., MLST). We recommend a full characterization MLST for a correct strain typing, while, based on the current data set, use of a single MLST gene can be effective for supergroup designation of A and B strains. Finally, we note that the sharing of wsp sequences between A and B strains indicates a strong genetic cohesiveness of Wolbachia strains, supporting designation of these bacteria within the same species, W. pipientis.
authors.affiliation: Department of Biology, University of California, 900 University Avenue, Riverside, CA 92521, USA. laurab@ucr.edu
authors.forename: Laura
authors.initials: L
authors.lastname: Baldo
authors.forename: John H
authors.initials: JH
authors.lastname: Werren
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D015373:Bacterial Typing Techniques / Q000379:methods*; D004269:DNA, Bacterial / Q000235:genetics; D005838:Genotype; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D020577:Wolbachia / Q000145:classification* / Q000235:genetics*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; C112171:Wsp protein, Wolbachia