The bacteriophage WORiC is the active phage element in wRi of Drosophila simulans and represents a conserved class of WO phages

In this study specific primers were designed to distinguish between these four prophage types in wRi, and quantitative PCR was used to measure the titer of bacteriophages in testes, ovaries, embryos and adult flies. In all tissues tested, WORiA and WORiB were not found to be present in excess of their integrated prophages; WORiC, however, was found to be present extrachromosomally. WORiC is undergoing extrachromosomal replication in wRi. The density of phage particles was found to be consistent in individual larvae in a laboratory population. The WORiC genome is organized in conserved blocks of genes and aligns most closely with other known lytic WO phages, WOVitA and WOCauB.The results presented here suggest that WORiC is the lytic form of WO in D. simulans, is undergoing extrachromosomal replication in wRi, and belongs to a conserved family of phages in Wolbachia.Wolbachia pipientis is an obligate bacterial endosymbiont of insects with a wide distribution. It is a member of the order Rickettsiales and is closely related to the insect vectored mammalian pathogens Anaplasma and Ehrlichia. Ten supergroups of Wolbachia have been identified within the species W. pipientis [1]. Supergroups A and B are common insect symbionts which probably diverged from one another 50-60 MYA [2]. The rapid spread of Wolbachia through insect populations is enhanced by symbiont-driven modifications to normal host reproductive patterns which are manifested as cytoplasmic incompatibility (CI), parthenogenesis, male killing and feminization (reviewed in [3]).The possibility of genetically transforming fastidious obligate intracellular bacteria and targeting them to insect vectors of human disease has stimulated renewed interest in Wolbachia's bacteriophage WO. The Wolbachia of Drosophila simulans, wRi, has acquired four prophage elements that are integrated into the bacterial genome as 18- to 77-kb sequences, termed wRi-WO-A, wRi-WO-B (two identical copies) and wRi-WO-C [4]. In contrast wMel