Bacterial stem cells for enhancing biodiesel production from lignocellulosic feedstocks

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The goal of this project is to genetically program bacterial cells to make large quantities of triacylglycerol (TAG), a commodity chemical that can be converted to biodiesel and industrial solvents. The bacterial species that will be used to make TAG, called Rhodococuus opacus, is particularly good at converting the energy in woody and fibrous plant matter (i.e. lignocellulosic feedstocks) into other molecules. However, a challenge is that the optimal conditions for TAG synthesis are not conducive to cell growth, thus production is self-limiting. This project seeks to solve this problem by transforming Rhodococcus strains into multicellular systems, where the tasks of population growth and TAG production are assigned to different cell types. If the strains produce more TAG, they could be used to increase the efficiency of U.S. agriculture by transforming wasted plant material into useful fuel. This project also contributes to undergraduate biosciences education through the development of augmented reality-based classroom technology. Here, holographic three-dimensional video imagery is used in combination with pass- through visualization to create a vibrant and highly interactive social learning environment. Within shared, augmented reality learning spaces, students collaborate in small teams to enhance learning through lessons in enzyme pathways and enzyme kinetics.The technological approach centers on the idea of enhancing Rhodococcus by inserting a genetically engineered system that enables two independently programmable cell types. With independently controllable cell types, it is possible to carry out mutually antagonistic tasks simultaneously. In this project, the two mutually antagonistic tasks are high-level triacylglycerol (TAG) production, which requires that cells undergo nitrogen deprivation and stop dividing, and population growth, which requires nitrogen. For maximal production, one cell type, called a “factory cell”, is programmed to stop incorporating nitrogen and expend all available metabolic resources to make TAG. The other cell type, called a “stem cell”, is programmed to import nitrogen and divide asymmetrically. After each stem cell division, one daughter retains stem cell fate while the other furthers TAG production by differentiating into a factory cell. The continual generation of healthy new factory cells from the dividing stem cell population is expected to prolong TAG synthesis and lead to higher overall yield.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.