MIP. Temperature Adaptation of Autotrophic Carbon Metabolism in Ecologically Diverse Hot Spring Synechococcus: An Integrative Study of Extreme Photosynthesis

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A grant has been awarded to Dr. Scott R. Miller of The University of Montana to investigate the mechanisms of physiological adaptation among members of a closely related group of photosynthetic hot spring bacteria that differ in temperature tolerance. Because organisms cannot perform equally well in all possible environments, understanding both the limits to performance and how physiological differences develop among microorganisms remains a fundamental goal for the study of microbial diversity. Proteins that affect performance can generally either be more stable at higher temperatures or work faster at lower temperatures, but not both. This project specifically addresses the contributions of this trade-off at the protein level to the physiology and thermal ecology of these bacteria for a key protein in the photosynthetic process: ribulose bis-phosphate carboxylase (Rubisco): (1) Rubisco stability and function at different temperatures will be determined by physiological, biochemical and biophysical approaches for modern-day versions of this protein isolated from these bacteria; (2) specific ancestral versions of Rubisco that represent incremental steps in the evolution of this protein during the diversification of these bacteria will be constructed genetically using a targeted mutational approach; (3) stability and function of these ancestral Rubisco versions will be determined to test whether particular compositional changes during its evolution have conferred stability at higher temperatures and/or a decreased rate of performance at lower temperatures.