A large body of research has worked to understand host-microbe interactions in the human body, and we’ve discovered that a dysbiosis of the microbial community can lead to disease. Due to these immense impacts, both positive and negative, the importance of understanding these interactions is vital. However, studying the mechanistic underpinnings of how microbes communicate with their host still has many challenges. One mechanism that microbes use to communicate and interact with eukaryotic hosts are outer membrane vesicles (OMVs) which are produced by many different species of bacteria including human pathogens and marine bacteria. These vesicles have been shown to transfer toxins, genetic material like DNA or virulence factors as well as lipids, proteins, and small molecules. An interesting candidate to investigate OMVs is the Roseobacter clade of bacteria due to their prevalence in marine ecosystems. Roseobacter often colonize marine biofilms and are a known inducer of settlement in several marine invertebrates. An emerging model to study host-microbe interactions is the marine tubeworm Hydroides elegans, which develop responses to one bacterial cue at a time and is the only model that requires bacterial products to stimulate its metamorphosis and growth. Understanding the factors that induce metamorphosis can give us a direct link to how microbes are interacting with eukaryotic organisms. How I will explore this interaction is to interrogate genes associated with OMVs including lipopolysaccharides (lpsC) and exopolysaccharides (exoP) to determine if these pathways are involved in the induction of metamorphosis. To do this I will employ CRISPR interference (CRISPRi) technology which utilizes a dead Cas9 protein to inhibit the expression of my target gene without making any edits to the genome. The results of this study will help characterize the unknown mechanism of how Roseobacter clade bacteria induce metamorphosis in Hydroides. OMVs have been shown to be prevalent in the human body and future applications of this research could use OMVs to deliver specific cargo in human microbial systems as a therapeutic avenue.