Absence of the Filarial Endosymbiont Wolbachia in Seal Heartworm (Acanthocheilonema spirocauda) but Evidence of Ancient Lateral Gene Transfer

The symbiotic relationship of Wolbachia spp. was first observed in insects and subsequently in many parasitic filarial nematodes. This bacterium is believed to provide metabolic and developmental assistance to filarial parasitic nematodes, although the exact nature of this relationship remains to be fully elucidated. While Wolbachia is present in most filarial nematodes in the familyOnchocercidae, it is absent in several disparate species such as the human parasite Loa loa. All tested members of the genusAcanthocheilonema, such as Acanthocheilonema viteae, have been shown to lack Wolbachia. Consistent with this, we show thatWolbachia is absent from the seal heartworm (Acanthocheilonema spirocauda), but lateral gene transfer (LGT) of DNA sequences between Wolbachia and A. spirocauda has occurred, indicating a past evolutionary association. Seal heartworm is an important pathogen of phocid seals and understanding its basic biology is essential for conservation of the host. The findings presented here may allow for the development of future treatments or diagnostics for the disease and also aid in clarification of the complicated nematode–Wolbachia relationship

Identification of clock gene functional conservation between Caenorhabditis elegans and Brugia malayi

Lymphatic filariasis is one the World Health Organization\u27s Big Seven neglected tropical diseases which currently affects 120 million people across 73 endemic nations1. The primary clinical manifestations of lymphatic filariasis include elephantiasis and severe lymphedema that trigger permanent deformation and disability of the afflicted tissues21. Permanent disability consequentially perpetuates chronic poverty, and has prompted the World Health Organization to set disease elimination as a Millennium Development Goal21,23. Current treatment regimens are ineffective against the infective third-stage larvae and the reproductively active adult parasites21,24. Thus, an increased need exists for anti-helminthic therapies that can either kill microfilariae, third-stage larvae, or disrupt transmission and reproductive behavior. The filarial nematode Brugia malayi, responsible for 10 % of all reported cases, exhibits periodic patterning in both adult female egg-laying, and microfilariae movement that has yet to be examined by molecular methods8, 29. Both behaviors are deemed critical for effective parasite transmission, and appear to be entrained to a consistent 24-hour patterning. Because underlying molecular regulators of such behaviors have been identified in a diverse range of phyla, we suggest that a conserved molecular network regulates the observed circadian periodicity of B. malayi transmission and reproduction. We have thus far identified, by use of comparative genomics, two major circadian clock gene candidates that may participate in B. malayi periodicity. These were identified by similarity to well-documented Caenorhabdiditis elegans clock genes. We have experimentally amplified these gene sequences, and generated bacterial constructs that will be used for phenotypic assessment of B. malayi candidate protein function following generation of C. elegans transgenic lines. This thesis lays the foundation for further research to molecularly characterize clock gene functionality in B. malayi