In Escherichia coli, lambdoid prophages are stably integrated into the host chromosome and do not undergo lytic induction until the bacterial SOS response is activated [27]. Gavotte et al [17] used a filtration-based purification method accompanied by TEM and ORF7-specific PCR to show that mature phage particles form in Wolbachia-infected tissues in both D. simulans and D. melanogaster, but the specific identity of these virus particles and the regulation of their induction was not addressed. In this study, the activity of the three distinct

check details prophages found in wRi infecting D. simulans was measured using quantitative PCR. Phage type-specific primers were used to determine how many copies of the phage genomes were present in addition to the integrated forms. The only phage chromosome to appear in excess of the integrated

copy number was WORiC. The average number of copies of WORiC in all tissues tested ranged from 1.29 – 1.61 copies per Wolbachia, consistently above the one copy integrated into the wRi genome. Thus, WORiC appears to be the only actively replicating phage in D. simulans. wRi is considered to be a high CI strain of BIBW2992 molecular weight Wolbachia in D. simulans; embryonic lethality resulting from crosses between infected males and uninfected selleck products females is typically between Ponatinib 90 – 100% [28, 29]. In N. vitripennis infected with wVitB, which is also a high CI-inducing strain of Wolbachia, Bordenstein et al [15] reported an average WOVitB copy number of 1.6 ± 0.12 per Wolbachia. In the present study, a similar relative density of WORiC suggests that this phage is the active virus observed in past TEM micrographs of Drosophila tissues [5, 17]. WORiC genes have been reported as actively transcribed in previous literature. Specifically,

the ankyrin related genes in WORiC are expressed in males, females, ovaries, testes, early (2 hour AEL) and late (overnight) embryos [4]. WORiB and WORiA are non-functional phage remnants WORiA and WORiB did not show any evidence of extrachromosomal DNA beyond the one and two copies, respectively, found within the wRi genome. Alignments to WOCauB and WOVitA1 show that both WORiA and WORiB lack the core structural components necessary for virion assembly. The persistence of WORiA and WORiB within the wRi genome suggests that there may be selective pressures maintaining these two prophages. There is evidence that WORiB is actively transcribing at least one ORF located within the prophage genome [30] and so this region may be necessary for another, unrelated, aspect of Wolbachia biology.