Sponsored Projects for Undergraduate Research

Bacteriophages (phages) are viruses of bacteria that infect and replicate prior to lysing their host. There are two primary types of bacteriophages: (1) temperate phage and (2) lytic phage. Temperate phages integrate their genome into the bacterial cell (then called a lysogen) and can be either replicate alongside the host genome during host cell division or it can excise from the host genome, replicate and lyse the host cell. Lytic phages, however, are unable to integrate into the host genome and can only replicate by replicating inside the host and lysing the host cell to release the virions.

Increasing evidence, however, points to the idea that lytic phage may be able to pause replication. This would mean that after infection of the lytic phage genome, it circularizes and then lingers in the host cytoplasm, similar to a plasmid. The advantage to this is similar to that of a temperate phage – the phage can withstand otherwise hostile environmental conditions, persisting in the host cell and passed on vertically to a single daughter cell (rather than replicated as part of the genome as it is with an integrated temperate phage). When conditions improve, the phage can then replicate and lyse the host cell. This method of paused lytic replication is often referred to as pseudolysogeny and it is virtually unstudied experimentally.

In this project we will use a library of phage and bacteria to measure rates of pseudolysogeny. Using a vetted protocol of a simple plaquing assay, the aim is to compare rates of pseudolysogeny between the different hosts and across different phage to identify potential drivers of pseudolysogeny.