Lexie Cutter

Chlamydia are obligate intracellular bacteria which has an immense impact on public health. It grows and is propagated between cells and hosts through a phylum defining bi-phasic developmental cycle. A major challenge to the field has been understanding how this developmental cycle is regulated to enable this growth and disease processes. One system that has been shown to be critical for regulating the development cycle of Chlamydia is the Rsb system. Importantly, genetic disruptions of this system render gross defects in growth and completion of the chlamydial developmental cycle. In Chlamydia, this is a three-component partner switching system that relies on the phosphorylation state of an intermediate (RsbV) and the competing actions of a periplasmic sensor phosphatase (RsbU) and terminal protein partner kinase (RsbW). Based upon current observations, this system is hypothesized to sense levels of alpha-ketoglutarate and regulate the activity of the primary sigma factor to promote growth of Chlamydia. The model links host metabolism with the general growth of Chlamydia. Our recent data have shown that this periplasmic sensor binds to alpha-ketoglutarate, a key TCA intermediate, which is hypothesized to control cytosolic phosphatase activity. One of my dissertation goals is to experimentally evaluate the phosphatase activity relative to levels of alpha-ketoglutarate. This phosphatase activity is directed to the intermediate protein, RsbV, which is phosphorylated on serine 56. I am also focused on evaluating the role of this phosphorylation through introducing substitutions at this site (e.g., S56A). Lastly, the terminal components of this system, RsbW, is hypothesized to bind to and inhibit the primary sigma factor and growth of Chlamydia. My dissertation efforts will also include an investigation of this hypothesis directly in Chlamydia.