title: "Candidatus Cryptoprodotis polytropus," a novel Rickettsia-like organism in the ciliated protist Pseudomicrothorax dubius (Ciliophora, Nassophorea).
abstract: Rickettsia-like organisms (RLO) are obligate, often highly fastidious, intracellular bacterial parasites associated with a variety of vertebrate and invertebrate hosts. Despite their importance as causative agents of severe mortality outbreaks in farmed aquatic species, little is known about their life cycle and their host range. The present work reports the characterization of "Candidatus Cryptoprodotis polytropus," a novel Rickettsia-like bacterium associated with the common ciliate species Pseudomicrothorax dubius by means of the "Full-Cycle rRNA Approach" and ultrastructural observations. The morphological description by in vivo and scanning electron microscopy and the 18S rRNA gene sequence of the host species is provided as well. Phylogenetic analysis based on the 16S rRNA gene supports the inclusion of "Candidatus Cryptoprodotis polytropus" within the family Rickettsiaceae (cl. Alphaproteobacteria) together with the genera Rickettsia and Orientia. Observations on natural ciliate populations account for the occasional nature of this likely parasitic association. The presence of a previously unknown RLO in ciliates sheds a new light on the possible role of protists as transient hosts, vectors or natural reservoir for some economically important pathogens.
authors.affiliation: Department of Biology, Protistology and Zoology Unit, University of Pisa, Via A. Volta 4/6, I-56126 Pisa, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Ferrantini
authors.forename: Sergei I
authors.initials: SI
authors.lastname: Fokin
authors.forename: Letizia
authors.initials: L
authors.lastname: Modeo
authors.forename: Ilaria
authors.initials: I
authors.lastname: Andreoli
authors.forename: Fernando
authors.initials: F
authors.lastname: Dini
authors.forename: Hans-Dieter
authors.initials: HD
authors.lastname: Görtz
authors.forename: Franco
authors.initials: F
authors.lastname: Verni
authors.forename: Giulio
authors.initials: G
authors.lastname: Petroni
mesh_terms: D001483:Base Sequence; D016798:Ciliophora / Q000235:genetics* / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D020459:Genes, rRNA; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D007558:Italy; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D012287:Rickettsiaceae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification* / Q000648:ultrastructure; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D016054:DNA, Protozoan; D012336:RNA, Ribosomal, 16S; D012337:RNA, Ribosomal, 18S