Probing the cryptic nitrogen cycle

探索神秘的氮循环

• 批准号: NE/V007785/1
• 负责人: Mark Trimmer
• 金额: $ 10.06万
• 依托单位: Queen Mary University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FV007785%2F1
• 关键词: Probing; cryptic; nitrogen; cycle

The element nitrogen (N) is key to life - building proteins and the very DNA that tells life what to do. Nitrogen exists largely as di-nitrogen gas (N2) in the atmosphere, with a fraction being present in the organic N of life (humans, animals, plants, microbes etc.). Following death and decay, organic N decomposes to ammonia. The N in ammonia is then cycled back to the atmosphere through a coupling between microbes (microscopic organisms known as bacteria and archaea) that, on the one-hand, use oxygen to convert ammonia into nitrates and, on the other, microbes that respire nitrate in the absence of oxygen back to N2 gas. Oxygen rich, oxic-habitats are all around us, be it agricultural, grassland or forest soils or, indeed, your own back garden. If those soils become water logged, they will lose their oxygen and become anoxic-habitats and the same holds true for muddy sediments at the bottom of seas and lakes - and microbes in those anoxic habitats respire nitrates to N2 gas. This is the N cycle taught at school and although it has been updated in the past 20 years to include novel microbial pathways of producing N2 gas - the coupling between ammonia and N2 gas mediated through nitrates sits at its very heart.What's new? In 2016, Trimmer and his grouped published a paper showing that the division between the recognised oxic and anoxic parts of the N cycle was blurred, with ammonia being converted to N2 gas in clean, oxygen-rich gravel riverbeds. Subsequently, Trimmer had a PhD student continue to explore the N cycle in oxygen-rich gravel riverbeds. The opportunity now for a new international collaboration arouse fortuitously during the examination that PhD student by the external examiner Prof. Bo Thamdrup (University of Southern Denmark) who identified a mistake in an equation in Liao's thesis. Correcting this seemingly innocuous mistake turned out to have profound implications for our understanding of the N cycle; though not only in oxic riverbeds but in many other habitats that drive the Earth's N cycle. What has changed? Correcting the equation led to a new mathematical framework and placing our data into that new framework showed that the patterns in the N2 gas data - in the PhD thesis - disagreed with those expected for a coupling between distinct oxic and anoxic steps in the N cycle. Where that well-recognised coupling should include nitrates, our new mathematical framework argues for a cryptic-coupling that does not involve nitrates.Why does this matter? A cryptic-coupling not only changes our view of a fundamental step in the N cycle but - being hidden - a cryptic-coupling undoes 20 years' of research into the different microbial pathways that make N2 gas and our overall understanding of the N cycle is now challenged. Our new framework suggests a new pathway or at least a new type of coupling between known pathways in the N cycle that needs to be characterised before we can understand the cycling of a key bio-element on Earth. Further, unravelling this cryptic-coupling could facilitate the development of more efficient waste-water treatment i.e., by removing the need for separate oxic and anoxic treatment processes. We cannot, however, probe this new cryptic-coupling in the N cycle using current and widely available techniques - as they are simply blind to what it is we need to study. Hence, now in a new international collaboration we will pioneer the development of new tools to probe a cryptic-coupling in the N cycle. We will share complimentary mass-spectrometer facilities, along with contrasting field-sites and novel isotope and molecular techniques to deliver new fundamental and applied knowledge about the all too common, yet still enigmatic cycling of N on Earth.

元素氮（n）是生命的关键 - 构建蛋白质和告诉生活该怎么做的DNA。氮主要作为大气中的二氮气（N2）存在，生命的有机n（人类，动物，植物，微生物等）中存在一小部分。死亡和腐烂后，有机n分解为氨。然后，通过微生物（称为细菌和古细菌的微生物之间的耦合）将氨中的N循环回到大气中，这些耦合单只手中使用氧气将氨转化为硝酸盐，而在其他的微生物上，在没有氧气的情况下将硝酸盐转化为硝酸盐，而没有氧气回到N2燃气中。无论是农业，草原还是森林土壤，还是您自己的后花园。如果这些土壤成为水记录，它们将失去氧气并变成缺氧狂的人，并且对于海洋和湖泊底部的泥泞的沉积物而言，它们也是如此，而在那些缺氧栖息地中，微生物在N2气体上均具有硝酸盐。这是在学校教授的N周期，尽管在过去的20年中已经对其进行了更新，包括新的微生物途径产生N2气体 - 氨和通过硝酸盐介导的N2气体之间的耦合坐在其心中。什么是新的？ 2016年，Trimmer和他的小组发表了一篇论文，表明N循环的公认的毒性和缺氧部分之间的分裂被模糊，氨被转化为N2气体，以清洁，富含氧气的砾石河床转化为N2气体。随后，Trimmer有一个博士生继续探索富含氧气的砾石河床的N周期。现在，新的国际合作的机会在考试中幸运地引起了外部审查员Bo Thamdrup教授（丹麦大学）的博士学位学生，后者在Liao论文的一个方程式中确定了一个错误。纠正这个看似无害的错误对我们对N周期的理解具有深远的影响。虽然不仅在塞河床上，而且在许多其他驱动地球n周期的栖息地中。发生了什么变化？纠正方程式导致了一个新的数学框架，并将我们的数据放入该新框架中表明，N2气体数据中的模式 - 在博士学位论文中 - 与n周期中不同氧气和缺氧步骤之间耦合的期望的模式不同意。良好认可的耦合应包括硝酸盐，我们的新数学框架主张不涉及硝酸盐的隐性耦合。一个隐秘的耦合不仅改变了我们对N周期中基本步骤的看法，而且 - 被隐藏 - 对不同的微生物途径进行了20年的研究，该研究使N2气体和我们对N周期的整体理解现在受到挑战。我们的新框架提出了一种新的途径，或者至少在N周期中已知途径之间的新类型的耦合需要进行表征，然后才能理解地球上关键的生物元素的循环。此外，阐明这种隐秘耦合可以促进更有效的废水处理，即通过消除对单独的毒性和缺氧治疗过程的需求。但是，我们不能使用当前且广泛可用的技术在N周期中探测这种新的密码耦合 - 因为它们只是对我们需要研究的内容而视而不见。因此，现在，在新的国际合作中，我们将开发开发新工具，以探测N周期中的隐秘耦合。我们将共享免费的质谱仪设施，以及对比鲜明的现场位点以及新型的同位素和分子技术，以提供有关所有太常见的新的基本知识和应用的知识，但仍在地球上n的神秘循环。