Investigating assembly dynamics of a bacterial photosynthetic system and its impact on light-harvesting efficiency

Arizona State University, Scottsdale AZ

Investigators

Abstract

Photosynthetic bacteria thrive in diverse environments and possess unique strategies to regulate photosynthesis under stress. As current knowledge of these regulatory mechanisms is limited, this project delves into the photosynthetic processes of these bacteria using a range of biophysical techniques to unlock valuable insights into the physical principles. The study of these simpler photosynthetic machines will provide insight into the evolution and adaptation of the photosynthetic molecular apparatus. This project will investigate the overall protein architecture and assembly dynamics of the green sulfur bacterial (GSB) photosynthetic supercomplex, focusing on light regulatory mechanisms. This project involves the training of graduate and undergraduate students, particularly those from underrepresented minority backgrounds, equipping them with the necessary skills to contribute to this cutting-edge research. In addition, this endeavor is intertwined with the BioSense Network platform, which will engage high-school teachers and students, to ignite their interest in the fields of science, technology, engineering, and mathematics. GSB are anaerobic photoautotrophs thriving in extreme conditions with low light intensity and scarce nutrients. They have developed a highly efficient system for harvesting and transducing photosynthetic energy. One system component is the chlorosome, a large, specialized, membrane-bound light harvesting system, that efficiently captures the limited number of photons available and transfers the energy to the reaction center. This project aims to uncover how GSB regulates this photosynthetic system to efficiently use minimal light for cellular needs, by studying the spatial organization and assembly dynamics of proteins, involved in maintaining and regulating photosynthetic energy transfer. Cutting-edge cryo-EM methods will be applied to study the assembly dynamics, while structural mass spectrometry (MS) will provide information about highly flexible and unstructured protein domains within the supercomplex. The spatial arrangement of relevant protein complexes will be visualized with Cryogenic electron tomography to determine their positions in the cellular context. The overall architecture and assembly dynamics of the GSB photosynthetic system will be determined under various light intensities to understand how the molecular assembly responds to changes in light levels while maintaining high levels of energy transfer efficiency. The knowledge gained from this project will shed light on energy flow within GSB and contribute to our understanding of molecular evolution in photosynthesis. This project is funded by the Molecular Biophysics program of the Molecular and Cellular Biosciences Division in the Biological Sciences Directorate. 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.