Taxonomic status of the intracellular bacterium Wolbachia pipientis

Wolbachia pipientis is a maternally inherited, intracellular bacterium found in more than 20 % of all insects, as well as numerous other arthropods and filarial nematodes. It has been the subject of a growing number of studies in recent decades, because of the remarkable effects it has on its arthropod hosts, its potential as a tool for biological control of arthropods of agricultural and medical importance and its use as a target for treatment of filariasis. W pipientis was originally discovered in cells of the mosquito Culex pipiens and is the only formally described member of the genus. Molecular sequence-based studies have revealed a number of phylogenetically diverse strains of W pipientis. Owing to uncertainty about whether W pipientis comprises more than one species, researchers in the field now commonly refer to W pipientis simply as Wolbachia. In this note, we briefly review higher-level phylogenetic and recombination studies of W pipientis and propose that all the intracellular symbionts known to cluster closely with the type strain of W pipientis, including those in the currently recognized supergroups (A-H), are officially given this name.