Although these symbiotic relationships share many common features at the whole-organism level, the molecular regulation of each

phase of the pathogenic/mutualistic interaction is dependent on both distinct and common pathways and effector Wnt inhibitors clinical trials molecules (Goodrich-Blair & Clarke, 2007). The amenability of these systems to experimental and genetic manipulation coupled with postgenomic approaches will undoubtedly reveal further insight into the regulation of pathogenesis and mutualism in these symbiotic associations (Goodrich-Blair & Clarke, 2007; Herbert & Goodrich-Blair, 2007; Clarke, 2008). The other example of a bacterial–nematode mutualism occurs between the endosymbiont, Wolbachia and members of the Onchocercidae family of filarial nematodes (Table 2), including medically important parasites of humans and animals (Taylor et al., 2010). Members of the genus Wolbachia, an alphaproteobacterial group most closely related to Ehrlichia, Anaplasma and Rickettsia species, are diverse and abundant endosymbionts Selleckchem JNK inhibitor of insects and other arthropods, where they mainly display a parasitic association. Yet in nematodes, the bacterium appears to have

become a mutualist, restricted to a subgroup of the family Onchocercidae (Taylor et al., 2005a). Surveys of nonfilarial nematodes have failed to detect Wolbachia outside of this group (Bordenstein et al., 2003), although some evidence for divergent Wolbachia-like sequences and structurally distinct bacteria has been reported in the plant parasitic Tylenchid nematode, Radopholus

similis (Haegeman et al., 2009). Reports of PCR amplification of Wolbachia sequence from the metastrongylid nematode Angiostrongylus cantonensis (Tsai et al., 2007) have not been reproduced and appear to be because of laboratory contamination (Foster et al., 2008). A more in-depth survey of subfamilies of the Onchocercidae supports the view that Wolbachia of arose late in the divergence of filarial nematodes. It is absent from all ancestral groups, and there are examples of the presence or absence of Wolbachia both within nematode genera and species (Ferri et al., 2011). Further evidence of a different tissue tropism and distribution in the more recently acquired Clade F group in Mansonella spp. also suggests a more complex evolutionary history and potentially more diverse symbiotic relationships than previously thought (Ferri et al., 2011). In filarial nematodes that host Wolbachia, most studies have naturally focused on the endosymbiont’s relationship with pathogenic nematode species, Brugia malayi, a lymphatic filarial parasite of humans, Onchocerca volvulus, the cause of human onchocerciasis or ‘river blindness’ and Dirofilaria immitis, the cause of dog heartworm disease (Kozek, 2005; Taylor et al., 2010).