These data suggest that geography may influence Wolbachia prevalence as reported previously for field populations of spider Hylyphantes graminicola [74]. Further research on the heterogeneous distribution of Wolbachia infection in field populations could shed more light on the functional role of this endosymbiont in tsetse flies biology, ecology and evolution. Genotyping – Wnt inhibitor phylogeny The MLST- and wsp-based sequence analysis indicates that all but one of the Wolbachia strains infecting Glossina species GSK621 clinical trial belong to supergroup A; the exception being the bacterial strain infecting G. p. gambiensis, which belongs to supergroup B. The supergroup A tsetse flies Wolbachia strains are members

of three separate and distantly related groups. Our results are in accordance with two previous studies that relied on just the wsp phylogeny but indicated a similar topology [42, 44]. The phylogenetic analyses strongly suggest the presence of distantly related Wolbachia strains in tsetse flies species and support the hypothesis that horizontal transmission of Wolbachia between insect species from unrelated taxa has extensively occurred, as has been reported in the spider genus Agelenopsis [70], in the wasp genus Nasonia

Temsirolimus cell line [71], in the acari genus Bryobia [40] and in the termites of genus Odontotermes [75]. On the other hand, the sibling species G. m. morsitans and G. m. centralis carry closely related Wolbachia strains, which have

identical ST and differ only in the sequence of the fast evolving wsp gene, which suggests host-symbiont co-divergence. In addition, field populations of G. m. morsitans from different locations of Africa harbor very closely related Wolbachia strains, suggesting that the geographical origin of their hosts did not impact significantly Wolbachia strain divergence. Our findings are in agreement with reports on dipteran hosts associated with mushrooms [76] and on the spider Hylyphantes graminicola [74]. Cytidine deaminase On the other hand, studies on fig wasps [77] and ants [78] showed considerable association between biogeography and strain similarity. Horizontal gene transfer The evolutionary fate of any host-bacterial symbiotic association depends on the modes of transmission of the bacterial partner, vertical, horizontal or both. Additionally, horizontal gene (or genome) transfer events may also be important. Our data suggest that at least three genes (16S rRNA, fbpA and wsp) of the Wolbachia strain infecting G. m. morsitans have been transferred to the host genome (Figures 3 and 4). This transfer is supported by the amplification of derivative copies of fbpA and 16S rRNA, and of wsp in tissues from tetracycline-treated G. m. morsitans (Figure 4). The results suggest that fbpA and 16S rRNA have been pseudogenized through the accumulation of deletions, consistent with previous studies [45, 46, 51].