A Novel Obligate Intracellular Gamma-Proteobacterium Associated with Ixodid Ticks, Diplorickettsia massiliensis, Gen. Nov., Sp. Nov

Abstract

BackgroundObligate intracellular bacteria of arthropods often exhibit a significant role in either human health or arthropod ecology.Methodology/Principal FindingsAn 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/SignificanceConsidering 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.

Discovery of Novel Rickettsiella spp. in Ixodid Ticks from Western Canada

“…However, phylogenetic analyses of sequence data of the 16S rRNA gene subsequently revealed that Rickettsiella grylli represented a sister taxon to two genera of Gammaproteobacteria: Coxiella and Legionella (12). As a consequence, the genus Rickettsiella was transferred from the Rickettsiales to the family Coxiellaceae within the order Legionellales (20), a placement that has been supported by other molecular studies (11,(21)(22)(23)(24)(25)(26)(27)(28)(29). Rickettsiella have been reported in a diverse range of arthropod hosts, including insects (e.g., beetles, flies, crickets, locusts, cockroaches, wasps, midges, moths, and aphids), collembolans, crustaceans (e.g., isopods and crabs), and arachnids (e.g., spiders, scorpions, ticks, and mites) (20,30).…”

Diversity of Bacterial Endosymbionts Associated with Macrosteles Leafhoppers Vectoring Phytopathogenic Phytoplasmas

“…The European sheep tick Ixodes ricinus is the most prevalent tick species in central Europe and is known to vector a number of human and animal pathogens such as Borrelia spp., Rickettsia helvetica, Rickettsia monacensis, Anaplasma phagocytophilum, Ehrlichia spp., Francisella tularensis, and others (55). Recently, a novel endocellular gammaproteobacterium was isolated from I. ricinus using mammalian and amphibian cell lines, which was allied to insect endosymbionts and pathogens of the genus Rickettsiella in the order Legionellales and was designated Diplorickettsia massiliensis (56). A large-scale serological survey detected three Diplorickettsia-positive cases of over 13,000 human serum samples (57), indicating its potential relevance to human health.…”

Current and Past Strategies for Bacterial Culture in Clinical Microbiology

“…More recently, growth of R. felis in Drosophila melanogaster S2 cells was reported, with a cell infection rate of 100% after 19 days of incubation at 25°C (331). Other arthropod-borne bacteria, such as Diplorickettsia massiliensis (332), Wolbachia sp., and Bartonella bacilliformis (40), as well as other bacteria such as Piscirickettsia salmonis (333) and M. ulcerans (334) can also be cultivated more effectively by using this cell line.…”