A novel obligate intracellular gamma-proteobacterium associated with ixodid ticks, Diplorickettsia massiliensis, Gen. Nov., Sp. Nov.
BACKGROUND
Obligate intracellular bacteria of arthropods often exhibit a significant role in either human health or arthropod ecology.


RESULTS
An obligate intracellular gamma-proteobacterium was isolated from the actively questing hard tick Ixodes ricinus using mammalian and amphibian cell lines. Transmission electron microscopy revealed a unique morphology of the bacterium, including intravacuolar localization of bacteria grouped predominantly in pairs and internal structures composed of electron-dense crystal-like structures and regular multilayer sheath-like structures. The isolate 20B was characterized to determine its taxonomic position using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that this strain belongs to the family Coxiellaceae, order Legionellales of Gamma-proteobacteria, and the closest relatives are different Rickettsiella spp. The level of 16S rRNA gene sequence similarity between strain 20B and other recognized species of the family was below 94.5%. Partial sequences of the rpoB, parC and ftsY genes confirmed the phylogenetic position of the new isolate. The G+C content estimated on the basis of whole genome analysis of strain 20B was 37.88%. On the basis of its phenotypic and genotypic properties, together with phylogenetic distinctiveness, we propose that strain 20B to be classified in the new genus Diplorickettsia as the type strain of a novel species named Diplorickettsia massiliensis sp. nov.


CONCLUSIONS
Considering the source of its isolation (hard tick, often biting humans) the role of this bacterium in the pathology of humans, animals and ticks should be further investigated.
Mediannikov
Oleg
O
Unité des Recherches sur les Maladies Infectieuses et Emergentes, Centre National de la Recherche Scientifique 6236, Institut de Recherche pour le Développement 198, Université de la Méditerranée, Marseille, France.
Sekeyová
Zuzana
Z
Birg
Marie-Laure
ML
Raoult
Didier
D
D000818:Animals; D001482:Base Composition / Q000235:genetics; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000648:ultrastructure; D026863:Ixodidae / Q000382:microbiology*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics
D012336:RNA, Ribosomal, 16S