Tissue and Stage-Specific Distribution of Wolbachia in Brugia malayi

Abstract

BackgroundMost filarial parasite species contain Wolbachia, obligatory bacterial endosymbionts that are crucial for filarial development and reproduction. They are targets for alternative chemotherapy, but their role in the biology of filarial nematodes is not well understood. Light microscopy provides important information on morphology, localization and potential function of these bacteria. Surprisingly, immunohistology and in situ hybridization techniques have not been widely used to monitor Wolbachia distribution during the filarial life cycle.Methods/Principal FindingsA monoclonal antibody directed against Wolbachia surface protein and in situ hybridization targeting Wolbachia 16S rRNA were used to monitor Wolbachia during the life cycle of B. malayi. In microfilariae and vector stage larvae only a few cells contain Wolbachia. In contrast, large numbers of Wolbachia were detected in the lateral chords of L4 larvae, but no endobacteria were detected in the genital primordium. In young adult worms (5 weeks p.i.), a massive expansion of Wolbachia was observed in the lateral chords adjacent to ovaries or testis, but no endobacteria were detected in the growth zone of the ovaries, uterus, the growth zone of the testis or the vas deferens. Confocal laser scanning and transmission electron microscopy showed that numerous Wolbachia are aligned towards the developing ovaries and single endobacteria were detected in the germline. In inseminated females (8 weeks p.i.) Wolbachia were observed in the ovaries, embryos and in decreasing numbers in the lateral chords. In young males Wolbachia were found in distinct zones of the testis and in large numbers in the lateral chords in the vicinity of testicular tissue but never in mature spermatids or spermatozoa.ConclusionsImmunohistology and in situ hybridization show distinct tissue and stage specific distribution patterns for Wolbachia in B. malayi. Extensive multiplication of Wolbachia occurs in the lateral chords of L4 and young adults adjacent to germline cells.

A new type F Wolbachia from Splendidofilariinae (Onchocercidae) supports the recent emergence of this supergroup

“…A recent analysis has shown that Wolbachia of supergroups C and D follow the same pattern of embryonic segregation, starting with mitotic asymmetric segregation to reach a subset of hypodermal cells (Landmann et al, 2010(Landmann et al, , 2012. From there, Wolbachia could invade the ovary and subsequently the germline (Fischer et al, 2011;Landmann et al, 2012). It was suggested that the presence of Wolbachia in the hypodermal cells of their filarial hosts may represent an ancestral somatic tissue-preference, reflecting their mechanism of horizontal transmission (Landmann et al, 2012).…”

“…To date, Wolbachia have not been identified in any other nematode groups (Bordenstein et al, 2003;Duron and Gavotte, 2007), although their presence was suggested in Radopholus similis, a plant-parasitic nematode (Haegeman et al, 2009). Filarial Wolbachia are usually found in the female reproductive apparatus and in the hypodermis (Brattig et al, 2001;Kramer et al, 2003;Landmann et al, 2010;Fischer et al, 2011). The endosymbiont is thought to be mutualistic and ubiquitous in Onchocercidae and to provide essential metabolites to the filariae (Foster et al, 2005;Strübing et al, 2010).…”

Species in Wolbachia? Proposal for the designation of ‘Candidatus Wolbachia bourtzisii’, ‘Candidatus Wolbachia onchocercicola’, ‘Candidatus Wolbachia blaxteri’, ‘Candidatus Wolbachia brugii’, ‘Candidatus Wolbachia taylori’, ‘Candidatus Wolbachia collembolicola’ and ‘Candidatus Wolbachia multihospitum’ for the different species within Wolbachia supergroups

“…The description of the species 'Candidatus Wolbachia brugii' is based on the studies reported by Fischer et al [34], and Landmann et al [57,58], and Taylor et al [92]. Cell size is 0.5 m up to 1 m. Cells are spherical or have an elongated shape and are surrounded with a double membrane.…”

Native microbiome impedes vertical transmission of Wolbachia in Anopheles mosquitoes

“…After microinjection into Drosophila, Wolbachia infects the stem cell niches in the germ line (16,17), and both Wolbachiaderived and host factors appear to influence tropism and bacterial density during oogenesis (17)(18)(19)(20). Alternatively, somatic tissue may act as a reservoir for Wolbachia infection of the developing oocyte (20)(21)(22)(23). Although pathways of horizontal transmission have been characterized in some species, identification of barriers to vertical transmission of the acquired Wolbachia infection remains elusive.…”