Enzymatic diversity of biological nitrogen fixation: above, below and beyond cyanolichens.

生物固氮（BNF）是氮循环的关键反应，也是非管理生态系统新氮的重要来源。该反应由三种异构体催化，基于钒的固氮酶和两种互补的固氮酶（comp-Nases）;基于钒的固氮酶和仅含铁的固氮酶。更好地评估固氮酶有助于生物固氮酶固定氮输入的估计和我们的理解之间的联系痕量金属动力学和生物固氮有重要意义。 目标-我的研究计划的长期目标（10-15年）是破译微量金属动力学和氮循环之间的联系。我的短期目标（未来5年）是在地球尺度上破译comp-Nases对BNF的发生和贡献。为了实现这一目标，在未来的5年里，我的研究计划的目标是：（1）评估comp-Nases对北方羽藓生物固氮的贡献，（2）评估comp-Nases对高等植物基质生物固氮的存在和贡献（3）研究了温度及其与钼有效性的交互作用对复合酶利用的影响，（4）在地球尺度上研究了复合型Nases的贡献;（5）估算了人类活动对Nases利用的影响（Mo-Nase与Comp-Nases）。方法-这项研究计划包括现场和实验室实验。它将依赖于一系列分析工具，用于生物基质中的元素分析，用于表征固氮酶基因的存在和表达以及固氮群落的分子生物学，以及用于评估生物固氮的分析化学。影响-这项研究计划将有助于缩小有关comp-Nases对BNF的作用和控制其使用的环境驱动因素的多个知识差距。在生态系统和地球尺度上破译化合物对生物固氮的发生和贡献具有潜在的变革性，因为它深刻影响了我们在该领域理解和估计生物固氮的方式。例如，大多数N输入估计值来自高度依赖固氮酶亚型的未校准乙炔还原测定。如果comp-Nases比以前认为的更重要，则需要对N输入估计进行深刻的重新评估。它还质疑我们对金属控制主要养分循环的理解（即，N）。钒很可能是生物圈的一种重要生物金属，与钼相比，钒的地球化学循环和与微生物的相互作用仍然很难表征。由于N输入估计用于多种目的，因此这项研究最终将帮助最终用户（例如，林业）和决策者，以改善加拿大的自然资源管理政策和做法。

Context - Biological nitrogen fixation (BNF) is a key reaction of the N cycle and an important source of new N to unmanaged ecosystems. This reaction is catalyzed by three isoforms, the molybdenum-based nitrogenase, and two complementary nitrogenases (comp-Nases); the vanadium based nitrogenase and the iron-only nitrogenase. Better evaluating which nitrogenases contribute to biological nitrogenase fixation has important implications for the estimation of N inputs and our understanding of the link between trace metal dynamics and BNF. Objectives - The long-term objective (10-15 years) of my research program is to decipher the link between trace metal dynamics and nitrogen cycling. My short term objective (next 5 years) is the decipher the occurrence and contribution of comp-Nases to BNF at the earth scale. To achieve this goal, over the next 5 years my research program aims at (1) evaluating the contribution of comp-Nases to boreal feather moss BNF, (2) assessing the presence and contribution of comp-Nases to BNF associated with higher plants matrices (phyllosphere and rhizosphere), (3) investigating the role of temperature, and its interaction with Mo availability, on the use of comp-Nases, (4) investigating the contribution of comp-Nases at the earth scale, (5) estimating how Mo of anthropogenic origin altered Nases use (Mo-Nase versus comp-Nases). Methodology - This research program includes both field and laboratory experiments. It will rely on a series of analytical tools for elemental analysis in biological matrices, molecular biology for the characterization of nitrogenase genes presence and expression and N2 fixing community, and analytical chemistry for the evaluation of BNF. Impact - This research program will contribute to close multiple knowledge gaps regarding the role of comp-Nases to BNF and the environmental drivers controlling their use. Deciphering the occurrence and contribution of comp-Nases to BNF at the ecosystem and earth scale is potentially transformative as it deeply affects the way we comprehend and estimate BNF in the field. For instance, most N input estimates derives from uncalibrated acetylene reduction assay which is highly nitrogenase isoforms dependent. If comp-Nases are more important than previously believed a profound reassessment of N input estimates will be required. It also questions our understanding of metals control over major nutrient cycling (i.e., N). Vanadium is likely a critical biometal for the biosphere which biogeochemical cycling and interactions with microorganisms remains poorly characterized, in comparison to its molybdenum counterpart. Because N input estimates are used for multiple purposes, this research will ultimately help end-users (e.g., forestry) and decision makers to improve Canadian natural resources management policies and practices.