Dissertations, Theses, and Capstone Projects

Date of Degree

9-2024

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Reza Khayat

Committee Members

Paul Gottlieb

Ruth Stark

John Dennehy

Enrique Rojas

Keywords

Virology, Cystovirus, Bacteriophage, Molecular Biology

Abstract

The Cystoviridae is a unique family of double stranded RNA bacteriophage that fuses its outer viral membrane with the lipopolysaccharide membrane of its Gram-negative host. In a series of studies, we determined the specifics of Cystoviridae host binding and the requirements of host fusion. The outer membrane vesicles (OMVs) secreted by the host inhibit Cystoviridae infection. We studied the interaction between OMVs and Cystoviridae to observe the host requirements for binding Cystoviridae. We determined that Cystoviridae strains Phi 8 and Phi 12 recognize the core polysaccharide and lipid A of the host lipopolysaccharide (LPS) for binding. The P6 protein of the Cystoviridae spike complex is suggested to allow fusion of the phage to the host cell. We investigated the P6 residues required for host fusion. The P6 residues of Phi 6 and Phi 12 that are required for fusion are predicted to be in alpha helices. We hypothesize that fusion occurs through coil-to-coil interactions. To observe details of the lifecycle of Phi 8 we utilized in situ cryo electron microscopy. Our results indicate the presence of Cystoviridae in different stages of capsid biogenesis. Lastly, we expressed different forms of the envelope forming protein P9 to purify vesicles containing P9. These vesicles have the potential to determine the P3 residues required for host binding.

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