Structural variation of the nitrogen-fixing heterocyst: Addressing the role of gas permeability in evolutionary divergence

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Nitrogen (N) fixation by microorganisms contributes enormous quantities of usable, life-sustaining N to natural and agricultural systems each year. Because oxygen irreversibly poisons the N-fixation machinery, managing oxygen exposure is a central problem for N-fixing organisms, which use oxygen to make energy. The cyanobacterial heterocyst is a specialized cell designed to provide both sufficient energy and an environment favorable for N fixation. Here, the investigators propose to use the heterocyst as a model to address how changing temperature shapes the form and function of biological structures, which manipulate gas exchange with the environment. Specifically, the investigators will combine chemical, physiological, and genetic approaches to test how naturally-occurring variation in heterocyst architecture associated with environmental temperature impacts the temperature-dependence of heterocyst function through the modification of oxygen flow into the heterocyst. The project promises novel and general insights into how this ecologically and economically important structure is affected by increasing temperature and its capacity for an evolutionary response in the face of environmental change. Because the heterocyst is also currently the best model for producing hydrogen energy from light, the project outcomes will have implications for how to engineer a reliable and affordable source of hydrogen. The project integrates research and education through mentoring and outreach at diverse levels, including a field course in Yellowstone that reveals the interdependence of microorganisms and wildlife for controlling N availability in the world's first national park.