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.
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Acknowledgments
We thank Nadia Ayoub for providing Agelenopsis specimens. Funds from the U.S. National Science Foundation grant EF-0328363 supported J.W.
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Baldo, L., Werren, J.H. Revisiting Wolbachia Supergroup Typing Based on WSP: Spurious Lineages and Discordance with MLST. Curr Microbiol 55, 81–87 (2007). https://doi.org/10.1007/s00284-007-0055-8
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DOI: https://doi.org/10.1007/s00284-007-0055-8