Integrating population genomics and microbial metagenomics of the lone star tick, an expanding arthropod disease vector

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Integrating population genomics and microbial metagenomics of the lone star tick, an expanding arthropod disease vector PROJECT SUMMARY/ABSTRACT Ticks are the most important vectors of disease-causing pathogens in the United States. The lone star tick, Amblyomma americanum, is a competent vector of various pathogenic microorganisms. There are several critical knowledge gaps in our understanding of the basic biology of the lone star tick, an arthropod disease vector that is rapidly expanding its geographic distribution into the Midwest and Northeast. Little is known about how the diversity of the tick’s genome and the microbial diversity of the tick’s microbiome affect the ability of specific pathogens to infect a tick. The main objective of this research is to generate an integrated genetic epidemiology for tick-borne diseases that incorporates the genomic diversity of vector, the species diversity of its microbiome, and the prevalence of known pathogens. The overarching hypothesis is that genomic diversity of tick vectors is positively associated with microbial species diversity and negatively associated with pathogen prevalence. The Principal Investigator will use next-generation DNA sequencing to test the overarching hypothesis and achieve the main objective of this project through three specific aims: (1) Investigate the spatial distribution of genomic variation among populations of lone star tick near the western and northern species range boundaries. The working hypothesis is that a cline of genomic diversity corresponds to increasingly stressful climatic conditions at the edges of the species range, suggesting that range expansion coincides with microevolutionary change. (2) Characterize the microbiome of lone star tick and assess its relationship to host genomic diversity. The working hypothesis is that greater genomic diversity of ticks permits a greater microbial species diversity in ticks, suggesting that host genotype affects microbiome composition. (3) Examine the effects of genomic diversity and microbial diversity on pathogen infection in individual ticks. The working hypothesis is that high genomic and microbial diversity of individual ticks reduces infection by pathogenic bacteria, suggesting that competitive interactions of microbes inside of ticks govern the prevalence of specific tick-borne pathogens at broader scales. This study is innovative because it will (a) uniquely bridge methodologies in population genomics, bacterial metagenomics, and community ecology of vector-borne pathogens; (b) generate genomic data that will be a valuable resource for future investigations of A. americanum and other ticks; and (c) illuminate the importance of accounting for genomic and microbiome diversity in laboratory-reared ticks used in studies of pathogen transmission, host immunology, and acaricides. This study is significant because it will shed light on the microbial interactions within individual ticks that may influence pathogen dynamics. Discovering bacterial lineages or assemblages that competitively inhibit infection by pathogens within ticks will be a significant step in controlling diseases vectored by ticks and other arthropods. Furthermore, this proposed study will enhance the infrastructure for research at Pepperdine University and will provide crucial opportunities to undergraduate students interested in careers in biomedical sciences and vector biology.