title: Identification of vacuoles containing extraintestinal differentiated forms of Legionella pneumophila in colonized Caenorhabditis elegans soil nematodes.
abstract: Legionella pneumophila, a causative agent of Legionnaires' disease, is a facultative intracellular parasite of freshwater protozoa. Legionella pneumophila features a unique developmental network that involves several developmental forms including the infectious cyst forms. Reservoirs of L. pneumophila include natural and man-made freshwater systems; however, recent studies have shown that isolates of L. pneumophila can also be obtained directly from garden potting soil suggesting the presence of an additional reservoir. A previous study employing the metazoan Caenorhabditis elegans, a member of the Rhabditidae family of free-living soil nematodes, demonstrated that the intestinal lumen can be colonized with L. pneumophila. While both replicative forms and differentiated forms were observed in C. elegans, these morphologically distinct forms were initially observed to be restricted to the intestinal lumen. Using live DIC imaging coupled with focused transmission electron microscopy analyses, we report here that L. pneumophila is able to invade and establish Legionella-containing vacuoles (LCVs) in the intestinal cells. In addition, LCVs containing replicative and differentiated cyst forms were observed in the pseudocoelomic cavity and gonadal tissue of nematodes colonized with L. pneumophila. Furthermore, establishment of LCVs in the gonadal tissue was Dot/Icm dependent and required the presence of the endocytic factor RME-1 to gain access to maturing oocytes. Our findings are novel as this is the first report, to our knowledge, of extraintestinal LCVs containing L. pneumophila cyst forms in C. elegans tissues, highlighting the potential of soil-dwelling nematodes as an alternate environmental reservoir for L. pneumophila.
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Hellinga
authors.affiliation: Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 1X5.|Department of Medicine, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada, B3H 1X5.
authors.forename: Rafael A
authors.initials: RA
authors.lastname: Garduño
authors.affiliation: Department of Biological Sciences, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Kormish
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Tanner
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Deirdre
authors.initials: D
authors.lastname: Khan
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Kristyn
authors.initials: K
authors.lastname: Buchko
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Celine
authors.initials: C
authors.lastname: Jimenez
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Mathieu M
authors.initials: MM
authors.lastname: Pinette
authors.affiliation: Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2.
authors.forename: Ann Karen C
authors.initials: AK
authors.lastname: Brassinga
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000382:microbiology*; D041981:Gastrointestinal Tract / Q000382:microbiology; D006066:Gonads / Q000382:microbiology; D016952:Legionella pneumophila / Q000302:isolation & purification*; D046529:Microscopy, Electron, Transmission; D008857:Microscopy, Interference; D012987:Soil / Q000469:parasitology; D014617:Vacuoles / Q000382:microbiology*
chemical_list: D012987:Soil
keywords: Cyst biogenesis; LCV; Legionella; nematode; oocyte endocytosis pathway; protozoa