Bipolar Biogeographical Distribution of Parafrancisella Bacteria Carried by the Ciliate Euplotes

Parafrancisella adeliensis, a Francisella-like endosymbiont, was found to reside in the cytoplasm of an Antarctic strain of the bipolar ciliate species, Euplotes petzi. To inquire whether Euplotes cells collected from distant Arctic and peri-Antarctic sites host Parafrancisella bacteria, wild-type strains of the congeneric bipolar species, E. nobilii, were screened for Parafrancisella by in situ hybridization and 16S gene amplification and sequencing. Results indicate that all Euplotes strains analyzed contained endosymbiotic bacteria with 16S nucleotide sequences closely similar to the P. adeliensis 16S gene sequence. This finding suggests that Parafrancisella/Euplotes associations are not endemic to Antarctica, but are common in both the Antarctic and Arctic regions.

Diversity of the Bacterial and Viral Communities in the Tropical Horse Tick, Dermacentor nitens, in Colombia

Ticks are obligatory hematophagous ectoparasites that transmit pathogens among various vertebrates, including humans. The microbial and viral communities of ticks, including pathogenic microorganisms, are known to be highly diverse. However, the factors driving this diversity are not well understood. The tropical horse tick, Dermacentor nitens, is distributed throughout the Americas and it is recognized as a natural vector of Babesia caballi and Theileria equi, the causal agents of equine piroplasmosis. In this study, we characterized the bacterial and viral communities associated with partially fed Dermacentor nitens females collected using a passive survey on horses from field sites representing three distinct geographical areas in the country of Colombia (Bolivar, Antioquia, and Cordoba). RNA-seq and sequencing of the V3 and V4 hypervariable regions of the 16S rRNA gene were performed using the Illumina-Miseq platform (Illumina, San Diego, CA, USA). A total of 356 operational taxonomic units (OTUs) were identified, in which the presumed endosymbiont, Francisellaceae/Francisella spp., was predominantly found. Nine contigs corresponding to six different viruses were identified in three viral families: Chuviridae, Rhabdoviridae, and Flaviviridae. Differences in the relative abundance of the microbial composition among the geographical regions were found to be independent of the presence of Francisella-like endosymbiont (FLE). The most prevalent bacteria found in each region were Corynebacterium in Bolivar, Staphylococcus in Antioquia, and Pseudomonas in Cordoba. Rickettsia-like endosymbionts, mainly recognized as the etiological agent of rickettsioses in Colombia, were detected in the Cordoba samples. Metatranscriptomics revealed 13 contigs containing FLE genes, suggesting a trend of regional differences. These findings suggest regional distinctions among the ticks and their bacterial compositions.

Detection of Rickettsia Species, and Coxiella-Like and Francisella-Like Endosymbionts in Amblyomma americanum and Amblyomma maculatum from a Shared Field Site in Georgia, United States of America

Two abundant species of aggressive ticks commonly feed on humans in Georgia: the Gulf Coast tick (Amblyomma maculatum) and the Lone Star tick (A. americanum). A. maculatum is the primary host of Rickettsia parkeri, "Candidatus Rickettsia andeanae," and a Francisella-like endosymbiont (AmacFLE), whereas A. americanum is the primary host for R. amblyommatis, Ehrlichia chaffeensis, E. ewingii, and a Coxiella-like endosymbiont (AamCLE). Horizontal transmission of R. parkeri from A. maculatum to A. americanum by co-feeding has been described, and R. amblyommatis has been found infrequently in A. maculatum ticks. We assessed the prevalence of these agents and whether exchange of tick-associated bacteria is common between A. maculatum and A. americanum collected from the same field site. Unengorged ticks were collected May-August 2014 in west-central Georgia from a 4.14 acre site by flagging and from humans and canines traversing that site. All DNA samples were screened with quantitative PCR assays for the bacteria found in both ticks, and the species of any Rickettsia detected was identified by species-specific TaqMan assays or sequencing of the rickettsial ompA gene. Only R. amblyommatis (15) and AamCLE (39) were detected in 40 A. americanum, while the 74 A. maculatum only contained R. parkeri (30), "Candidatus Rickettsia andeanae" (3), and AmacFLE (74). Neither tick species had either Ehrlichia species. Consequently, we obtained no evidence for the frequent exchange of these tick-borne agents in a natural setting despite high levels of carriage of each agent and the common observance of infestation of both ticks on both dogs and humans at this site. Based on these data, exchange of these Rickettsia, Coxiella, and Francisella agents between A. maculatum and A. americanum appears to be an infrequent event.

Microbial community of Hyalomma lusitanicum is dominated by Francisella-like endosymbiont

Exploring tick associations with complex microbial communities and single-microbial partners, especially intracellular symbionts, has become crucial to understand tick biology. Of particular interest are the underlying interactions with biological consequences i.e. tick fitness, vector competence. In this study, we first sequenced the 16S rRNA bacterial phylogenetic marker in adult male ticks of Hyalomma lusitanicum collected from 5 locations in the province of Cáceres to explore the composition of its microbial community. Overall, 16S rRNA sequencing results demonstrated that the microbial community of H. lusitanicum is mostly dominated by Francisella-like endosymbionts (FLEs) (ranging from 52% to 99% of relative abundance) suggesting it is a key taxon within the microbial community and likely a primary endosymbiont. However, further research is required to explore the mechanisms underlying the interaction between FLEs and H. lusitanicum.

Detection of Francisella-like endosymbiont in Hyalomma rufipes from Ethiopia

The expanding family of Francisellaceae includes the genus Francisella, where several pathogen bacteria, e.g. the zoonotic F. tularensis, and different Francisella-like agents belong to. Francisella-like endosymbionts (FLEs) are widespread in hard and soft ticks and their pathogenicity is unknown. The examination of 296 ticks collected in Ethiopia was performed for the detection of F. tularensis and FLEs using polymerase chain reaction (PCR) assays based on the amplification of 16S rRNA, sdhA and tul4 gene fragments. FLE was described in one Hyalomma rufipes tick based on the 16S rRNA and sdhA gene sequences. The 16S rRNA gene fragment was identical with the ones detected previously in Rhipicephalus sanguineus and Hyalomma marginatum marginatum in Bulgaria. The presence of endosymbionts with identical 16S rRNA gene sequence in both Rhipicephalus and Hyalomma species further supports the hypotheses, that certain FLEs had independent evolution from their tick hosts.