FUNCTIONAL CHARACTERIZATION OF THE BACTERIAL MICROBIOME OF THE DERMACENTOR ANDERSONI TICK EXHIBITS INTERACTIONS WITH PATHOGEN ACQUISITION
Gall, Cory A.
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Ticks are obligate hematophagous arthropods that feed on vertebrates and are of importance due to their ability to inflict harm to humans and animals. In particular, ticks transmit pathogens throughout all continents and are labeled as principle vectors of zoonotic pathogens. Dermacentor andersoni, the Rocky Mountain wood tick, has been labeled a “veritable Pandora’s box of disease-producing agents” transmits several pathogens, including Rickettsia rickettsii. It is also a vector of Anaplasma marginale, the agent of anaplasmosis, the most widespread tick-borne pathogen of livestock worldwide. While many microorganisms colonize ticks, the majority is non-pathogenic and make up a microbial community, termed the microbiome. These endosymbionts play a role in tick physiology, fecundity, and pathogen acquisition and transmission. Our goal was to characterize the bacterial microbiome of Dermacentor andersoni ticks, while examining different ecological and to analysis the role that the microbiome has on pathogen acquisition. We have characterized the microbiome of two populations of D. andersoni ticks with differing vector susceptibility for A. marginale: Burns, Oregon had a high rate (60%) and Lake Como, Montana a low rate (20%). Our analysis has shown that the bacterial composition was tissue- and spatial-specific; however, generational variation was dependent on geographic location. Furthermore, our study showed that the microbiomes of laboratory-reared populations were not representative of the respective field population. These results have demonstrated that the bacterial microbiome of D. andersoni was dynamic with the ability to undergo significant change. Additionally, our study showed that the microbiome could be disrupted through antibiotic exposure. Ticks with an altered microbiome had similar A. marginale acquisition rates to untreated ticks, but Lake Como ticks had lower levels of the pathogen. We identified a negative correlation between high levels and proportions of the endosymbiont R. bellii and the levels of A. marginale. Additionally, we showed a positive relationship between symbiotic Francisella and pathogenic F. novicida. To conclude, understanding the behavior and ecology of the microbiome is an essential aspect of microbiome biology and critical component in order to effectively manipulate the microbiome for biocontrol. These findings warrant further investigation into the relationship between endosymbionts and pathogens.