Molecular Characterization of Wolbachia and its Impact on the Microbiome of Exotic and United States Ticks
Date of Award
Honors College Thesis
Shahid Karim, Ph.D.
Wolbachia endosymbionts are obligate intracellular bacteria in the phylum α-Proteobacteria. They infect approximately two-thirds of arthropods including insects and nematodes. These bacteria manipulate host reproductive biology through a series of mechanisms that include feminization of male progeny, parthenogenesis, male killing, and cytoplasmic incompatibility. These features make Wolbachia an effective agent of controlling insect populations, as previously reported in different mosquito species. Likewise, the bacteria have also shown promising ability to interfere with the ability of mosquitoes to transmit several viral pathogens. This study was conducted to fill an existing knowledge gap on the prevalence of Wolbachia in different tick species and also compare the microbiome of infected and uninfected ticks. A polymerase chain reaction (PCR) based assay was used to characterize Wolbachia endosymbionts from three United States tick species (Amblyomma americanum, Amblyomma maculatum, and Ixodes scapularis) and two exotic species (Hyalomma anatolicum anatolicum and Rhipicephalus microplus), by amplifying the 16S ribosomal RNA and heat shock (GroEL) genes of Wolbachia. This study employed multiple sequence alignment and phylogenetic trees to resolve evolutionary relationships between Wolbachia and other insects and arthropods. Microbiome analysis was done by using Illumina sequencing of the V1-V3 variable region of the bacteria 16S ribosomal RNA. Overall, a low prevalence of Wolbachia was found, but the identified strains showed close similarities to other Wolbachia species from Aedes aegypti, Aedes albopictus, and Chrysoma megacephala. Uninfected ticks were all lab-reared ticks, while all ticks found to be positive for Wolbachia were ticks collected from the wild. I also observed a distinct difference in the bacterial species composition between infected and uninfected ticks. The microbiome of Wolbachia infected ticks exhibited a low species richness and diversity as compared to that of uninfected ticks. This study revealed that ticks share similar Wolbachia endosymbionts with mosquitoes. In addition, it provides research on interactions between Wolbachia endosymbionts and tick species, which will subsequently direct targeted tick control.
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Bobo, Cailyn G., "Molecular Characterization of Wolbachia and its Impact on the Microbiome of Exotic and United States Ticks" (2020). Honors Theses. 702.