Phages are bacterial viruses found in every ecosystem. They were, and still are, essential for the development of molecular biology and biotechnology. During my Ph.D., I aim to elucidate the function of uncharacterized phage proteins to better understand the intracellular interactions between those obligate parasites and their bacterial host. One of the ways to study genes and proteins is to modify them and observe the resulting phenotypes. Phage genomes can only be engineered inside a host, when they are biologically active. Virulent phages are strictly lytic and as such, they never integrate into the host chromosome. This constrains the modification of their genome to the short infection cycle. I am currently working with the virulent lactococcal phage p2, a model for a predominant phage group in the dairy industry. It infects the Gram-positive bacterium Lactococcus lactis MG1363, also a model strain for basic research. I developed a tool based on CRISPR-Cas9 to edit the genome of phage p2. To study protein function in vivo, we can now efficiently generate gene knockouts and investigate microbiological parameters associated with phage replication. To further characterize the role of phage proteins, I study bacterial and viral protein synthesis during infection using mass spectrometry (MS)-based proteomics. With our collaborators (Ernst-Moritz-Arndt University, Germany), we have generated comprehensive data on protein synthesis over time in a culture of L. lactis MG1363 infected with either the wild-type phage p2 or a knockout phage.
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