Cells use structure to catalyze and facilitate the chemical reactions of metabolism. This principle is exemplified by the process of carbon dioxide assimilation in photosynthetic bacteria, which coordinate myriad biochemical components in space and time, in order to achieve a single physiological goal _ convert solar power into fixed chemical energy. Despite knowing many of the proteins involved in this process, it is poorly understood how coordinated function emerges from individual parts. To this end, the goal of my lab is to develop a holistic understanding of the carbon dioxide assimilation process in photosynthetic bacteria. Ultimately, our goal is to use this understanding for the synthetic biological improvement of photosynthesis. A challenge to any such cell biological investigation is the dearth of tools for rapidly and non-invasively measuring metabolic state. Here, I describe research efforts in our group _ with a focus on protein engineering _ aimed at developing new tools for measuring and controlling cellular physiology in vivo.