Dr. Courtney Ellison Department of Molecular Biology Princeton University Thursday, March 11, 2021 - 11:10am Online via Zoom Special Information: Please contact Nancy Perkins at firstname.lastname@example.org for Zoom link and passcode Type of Event: Department Seminars Abstract: Bacteria use extracellular appendages called type IV pili (T4P) for diverse behaviors including DNA uptake, surface sensing, virulence, protein secretion, and biofilm formation. Dynamic extension and retraction of T4P is essential for their function in these behaviors, yet little is known about the molecular mechanisms controlling these dynamics. Furthermore, due to difficulties in visualizing T4P in live cells, their exact function in many of these processes has remained unclear. Through the development of a labeling method to visualize T4P in live cells in real time, our work has addressed multiple outstanding questions related to T4P biology. Using this labeling method, we defined the mechanism by which individual cells use T4P to take up DNA during natural transformation. We furthermore developed the highly naturally transformable species Acinetobacter baylyi as a new model to dissect the molecular mechanisms of T4P dynamics and T4P localization, with implications for how these structures may contribute to multicellular interactions. This work provides insight into the mechanisms that govern diverse microbial behaviors important for bacterial physiology through direct observation of the T4P appendages that mediate them.