Viruses hijack their hosts for the purpose of viral propagation. They steal host-encodedmachinery to create a factory for virus production within the cell. At the final stage of viral infection, the newly produced viruses are released from the cell, poised to infect a new host and continue the cycle. A model virus, ICP1, is a lytic bacteriophage (or phage) specific to Vibrio cholerae. ICP1 rapidly produces approximately 100 progeny virions within 20 minutes of infection. It would be expected that subsequent infections by progeny phage would decimate the V. cholerae population. Counter to this expectation, a consistent co-existence between ICP1 and V. cholerae has been observed over tens of decades in their natural contexts of the human gut and estuaries. A major factor contributing to the bacterial persistence is a potent defense system specific to ICP1, the phage inducible chromosomal island-like element (PLE). PLE is a virus-like mobile genetic element, referred to as a phage satellite. Just as the phages they parasitize are dependent on their host cells, phage satellites are dependent on the phages they parasitize (helper phages) for their propagation. PLE requires ICP1-encoded products for PLE genome excision, replication, gene expression, and horizontal transfer via transduction. Previous work has described the molecular mechanisms underlying the early and middle stages of PLE’s lifecycle, but the later stages involving virion assembly and genome packaging have yet to be studied in such detail. The late stages of PLE’s lifecycle are the focus of this work. In the second chapter, we provide an overview of ICP1, its co-existence with V. cholerae, and summarize previous studies about its parasitic partner, PLE. Then, in Chapter 3, we explore how PLE hijacks ICP1 coat proteins to assemble smaller capsids that are more proportional to PLE’s genome size. We find that PLE’s TcaP protein binds ICP1’s coat, forcing the assembly of small capsids that cannot accommodate ICP1’s large genome, and that these smaller capsids are necessary for the efficient transfer of PLE’s smaller genome. Then, in Chapter 4, we describe how PLE employs Orf3 to directly inhibit ICP1’s large terminase to block ICP1 genome packaging. We outline how PLE’s Orf4, Orf5, and pac site contribute to the packaging of PLE’s genome. Together, these data describe how PLE pirates and manipulates ICP1 proteins to produce virions that horizontally transmit PLE’s genome while directly limiting the propagation of ICP1. This work provides molecular details that further define PLE’s role in protecting the V. cholerae population from ICP1.