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

微生物的固氮作用每年为自然和农业系统提供大量可用的、维持生命的氮。由于氧气不可逆地毒害了固氮机制，因此对利用氧气制造能量的固氮生物来说，控制氧气暴露是一个核心问题。蓝藻异囊是一种特殊的细胞，旨在提供足够的能量和有利于N固定的环境。在这里，研究人员建议使用异囊作为模型来解决温度变化如何塑造生物结构的形式和功能，从而操纵与环境的气体交换。具体来说，研究人员将结合化学、生理学和遗传学方法来测试与环境温度相关的异囊结构的自然变化如何通过改变进入异囊的氧气流量来影响异囊功能的温度依赖性。该项目有望对这种重要的生态和经济结构如何受到温度升高的影响及其面对环境变化的进化反应能力提供新颖而全面的见解。由于异囊体也是目前从光中产生氢能源的最佳模型，因此该项目的成果将对如何设计可靠且负担得起的氢来源产生影响。该项目通过不同层次的指导和推广将研究和教育结合起来，包括在黄石公园的一个实地课程，该课程揭示了微生物和野生动物之间的相互依存关系，以控制世界上第一个国家公园的氮素可用性。

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.