title: Ultrastructural characterization and multilocus sequence analysis (MLSA) of 'Candidatus Rickettsiella isopodorum', a new lineage of intracellular bacteria infecting woodlice (Crustacea: Isopoda).
abstract: The taxonomic genus Rickettsiella (Gammaproteobacteria; Legionellales) comprises intracellular bacteria associated with a wide range of arthropods including insects, arachnids and crustaceans. The present study provides ultrastructural together with genetic evidence for a Rickettsiella bacterium in the common rough woodlouse, Porcellio scaber (Isopoda, Porcellionidae), occurring in Germany, and shows that this bacterium is very closely related to one of the same genus occurring in California that infects the pill bug, Armadillidium vulgare (Isopoda, Armadillidiidae). Both bacterial isolates displayed the ultrastructural features described previously for crustacean-associated bacteria of the genus Rickettsiella, including the absence of well-defined associated protein crystals; occurrence of the latter is a typical characteristic of infection by this type of bacteria in insects, but has not been reported in crustaceans. A molecular systematic approach combining multilocus sequence analysis (MLSA) with likelihood-based significance testing demonstrated that despite their distant geographic origins, both bacteria form a tight sub-clade within the genus Rickettsiella. In the 16S rRNA gene trees, this sub-clade includes other bacterial sequences from woodlice. Moreover, the bacterial specimens from P. scaber and A. vulgare are found genetically or morphologically different from each of the four currently recognized Rickettsiella species. Therefore, the designation 'Candidatus Rickettsiella isopodorum' is introduced for this new lineage of isopod-associated Rickettsiella bacteria.
authors.affiliation: Julius Kühn Institute (JKI) - Federal Research Centre for Cultivated Plants, Institute for Biological Control, Heinrichstraße 243, 64287 Darmstadt, Germany.
authors.forename: Regina G
authors.initials: RG
authors.lastname: Kleespies
authors.affiliation: Department of Entomology and Graduate Program in Genetics, Genomics, and Bioinformatics, University of California, Riverside, CA 92521, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Federici
authors.affiliation: Julius Kühn Institute (JKI) - Federal Research Centre for Cultivated Plants, Institute for Biological Control, Heinrichstraße 243, 64287 Darmstadt, Germany; Institute for Microbiology and Biochemistry, Geisenheim University, Von-Lade-Straße 1, 65366 Geisenheim, Germany. Electronic address: andreas.leclerque@hs-gm.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Leclerque
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D044125:Coxiellaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005858:Germany; D033321:Isopoda / Q000382:microbiology*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S
keywords: Armadillidium vulgare; Isopod; Likelihood-based significance testing; Multilocus sequence analysis (MLSA); Porcellio scaber; Transmission electron microscopy (TEM); Woodlouse; ’Candidatus Rickettsiella isopodorum’; ’Rickettsiella armadillidii’; ’Rickettsiella porcellionis’