The Pathway of Dentrification

9307501 Averill反硝化作用是氮循环中的一个关键过程，它控制着植物（包括粮食作物）生长所需的氮量。 据估计，高达30%的肥料氮通过反硝化作用损失。 通过NO2、NO和N2将亚硝酸盐还原为N2的线性途径似乎是主要途径，尽管对于某些生物体存在与NO2直接还原为N20一致的证据。 所提出的研究的目的是阐明在生物学中NO2被还原为N2 O的途径。 具体目标包括：（1）使用同位素标记、化学捕获和动力学研究来检查一氧化氮还原酶的机制;（2）使用遗传技术来探测硝化细菌中亚硝酸还原酶/一氧化氮还原酶的相互作用，以确定功能性一氧化氮还原酶是否是通过无色杆菌（Achromobacter cycloclastes）进行反硝化所必需的，并阐明了铜和血红素cd 1的亚硝酸盐还原酶的金属中心的作用;（3）亚硝酸盐还原的机制的原型真核微生物，霉菌镰刀菌，它似乎利用细胞色素P-450作为亚硝酸盐还原酶的表征。 拟议的研究应该导致对不同生物如何利用氮氧化物作为终端电子受体的基本理解。 由于微生物是各种生物技术应用的有吸引力的候选者，包括废水治理，并且是温室气体N20的重要来源，因此这些结果也可能具有重大的实际意义。 ***

9307501 Averill Denitrification is a key process in the nitrogen cycle, which controls the amount of nitrogen available for growth of plants, including food crops. Estimates suggest that up to 30% of fertilizer nitrogen is lost via denitrification. A linear pathway for reduction of nitrite to N2 via NO2, NO and N2) seems to be the predominant one, although evidence consistent with direct reduction of NO2 to N20 exists for some organisms. The objective of the proposed research is to elucidate the pathway(s) by which N02 is reduced to N20 in biology. Specific goals include: (1) the use of isotope labelling, chemical trapping, and kinetics studies to examine the mechanism of nitric oxide reductase; (2) the use of genetic techniques to probe nitrite reductase/nitric oxide reductase interactions in denitrifiers, to determine whether a functional nitric oxide reductase is necessary for denitrification by Achromobacter cycloclastes, and to clarify the roles of the metal centers in the Cu- and heme cd1 -containing nitrite reductases; (3) characterization of the mechanism of nitrite reduction by a prototypical eukaryotic denitrifier, the mold Fusarium, which appears to utilize a cytochrome P-450 as a nitrite reductase. %%% The proposed research should result in a fundamental understanding of how diverse organisms utilize nitrogen oxides as terminal electron acceptors. Since denitrifiers are attractive candidates for a variety of biotechnological applications, including waste water remediation, and in addition are important sources of the greenhouse gas N20, these results are likely to have significant practical implications as well. ***