title: Germs within Worms: Localization of Neorickettsia sp. within Life Cycle Stages of the Digenean Plagiorchis elegans.
abstract: Neorickettsia spp. are bacterial endosymbionts of parasitic flukes (Digenea) that also have the potential to infect and cause disease (e.g., Sennetsu fever) in the vertebrate hosts of the fluke. One of the largest gaps in our knowledge of Neorickettsia biology is the very limited information available regarding the localization of the bacterial endosymbiont within its digenean host. In this study, we used indirect immunofluorescence microscopy to visualize Neorickettsia sp. within several life cycle stages of the digenean Plagiorchis elegans Individual sporocysts, cercariae, metacercariae, and adults of P. elegans naturally infected with Neorickettsia sp. were obtained from our laboratory-maintained life cycle, embedded, sectioned, and prepared for indirect immunofluorescence microscopy using anti-Neorickettsia risticiihorse serum as the primary antibody. Neorickettsiasp. was found within the tegument of sporocysts, throughout cercarial embryos (germ balls) and fully formed cercariae (within the sporocysts), throughout metacercariae, and within the tegument, parenchyma, vitellaria, uteri, testes, cirrus sacs, and eggs of adults. Interestingly, Neorickettsia sp. was not found within the ovarian tissue. This suggests that vertical transmission of Neorickettsia within adult digeneans occurs via the incorporation of infected vitelline cells into the egg rather than direct infection of the ooplasm of the oocyte, as has been described for other bacterial endosymbionts of invertebrates (e.g.,Rickettsia and Wolbachia).
authors.affiliation: Department of Biology, University of North Dakota, Grand Forks, North Dakota, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Greiman
authors.affiliation: Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Rikihisa
authors.affiliation: Children's Health, Sanford Research, Sioux Falls, South Dakota, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Cain
authors.affiliation: Department of Biology, University of North Dakota, Grand Forks, North Dakota, USA.
authors.forename: Jefferson A
authors.initials: JA
authors.lastname: Vaughan
authors.affiliation: Department of Biology, University of North Dakota, Grand Forks, North Dakota, USA vasyl.tkach@email.und.edu.
authors.forename: Vasyl V
authors.initials: VV
authors.lastname: Tkach
mesh_terms: D000825:Animal Structures / Q000382:microbiology; D000818:Animals; D006376:Helminths / Q000254:growth & development / Q000382:microbiology*; D008018:Life Cycle Stages; D008856:Microscopy, Fluorescence; D041102:Neorickettsia / Q000302:isolation & purification* / Q000502:physiology*; D013559:Symbiosis; D014200:Trematoda / Q000254:growth & development / Q000382:microbiology*