Phage-mediated horizontal gene transfer in Borrelia burgdorferi - PROJECT SUMMARY/ABSTRACT Lyme disease is caused by infection with the spirochete Borrelia (Borreliella) burgdorferi. These spirochetes are themselves infected by the phage ϕBB-1. Phages are viruses that infect bacteria and are the most ubiquitous biological entities on the planet. ϕBB-1 is a temperate phage, which has two types of replication: the lytic cycle involves assembly of phage particles followed by release outside of the bacterium and lysogenic cycle involves incorporation of the phage into the bacterial genome. The ϕBB-1 prophage are the cp32s, a large group of nearly identical 32-kb circular plasmids universally found in every species of Borrelia. The central hypothesis of this application is that ϕBB-1 phage drive horizontal gene transfer of antigens between B. burgdorferi strains and that this process maintains the spirochete in its reservoir host, allowing for reinfection of individuals. There have been very few studies on the biology of ϕBB-1 and its role in transduction, the movement of genetic material between individual B. burgdorferi spirochetes by the ϕBB-1 phage. We endeavor to uncover the mechanism regulating ϕBB-1 replication and the effect of transduction on the ability of B. burgdorferi to cycle between its tick vector and vertebrate host. The following specific aims are proposed to accomplish these research goals: 1) Measure horizontal gene transfer between heterologous Bb strains in the tick vector; 2) Define the role of ϕBB-1 in maintaining spirochete infectivity in previously infected mice; and 3) dissect the mechanism of the ϕBB-1 lysis/lysogeny decision. Genetic, genomic, biochemical, and transcriptomic approaches, as well as the tick-mouse model of Lyme disease, will be utilized to experimentally pursue these aims. In this innovative application, the team of PIs have generated compelling preliminary data and are in the unique position of having the experience, expertise, and experimental models to enhance the mechanistic understanding of ϕBB-1 biology, including the regulation of replication decisions and the consequences of transduction on the ability of B. burgdorferi to infect previously infected hosts. The long-term objective of this proposal is to understand the role of ϕBB-1 phage on B. burgdorferi microbiology and Lyme disease pathogenesis, which will lead to improved diagnostic, prevention, and treatment strategies because genetic diversity is required for the maintenance of B. burgdorferi in its tick-vertebrate cycle as well as for the reinfection of previous Lyme disease patients; this is relevant to the mission of the agency to “seek fundamental knowledge” for the sake of alleviating human disease.
