Endosymbiotic species have been associated with commensal, mutualistic, and parasitic interactions, however our understanding of these relationships is usually limited to well studied hosts. In tick species, studies that investigate microbial relationships have typically focused on commonly studied human pathogens. In this study, we examine the internal microbiome of the blacklegged tick (Ixodes scapularis), an important disease vector in the US. Additionally, we further investigate two potential endosymbionts, Wolbachia and Rickettsia. Antibiotics were administered to blacklegged ticks in order to determine survival of ticks with reduced or eliminated Rickettsia levels. Additionally, Wolbachia prevalence was investigated in relation to infection with three tick-borne pathogens and with a known parasitoid wasp, Ixodiphagus hookeri, which has been demonstrated in other tick species.
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Results/Conclusions
Rickettsia was the most abundant bacterial genus in blacklegged ticks and this high abundance, coupled with the finding of vertical transmission, suggest that Rickettsia provides a beneficial role. When antibiotics were administered there was a significant reduction in tick survival. Wolbachia was found in all life stages within 50% of tick samples. Adult male ticks had a higher prevalence than females and given the role that some species of Wolbachia play in various arthropods (male sterility and reproductive manipulation), this suggests that there may be similar sex-related associations occurring in this tick. Additionally, we found no association between tick-borne pathogens and parasitoid wasp infection with Wolbachia, despite these findings in other tick species. This study provides the first steps in understanding the role that non-pathogenic, bacterial taxa play in this important disease vector and could eventually help us understand possible internal controls on tick survival and subsequent disease risk.