Identification of metabolic and enzymatic pathways in the phosphorous cycle using triple oxygen isotope systematics

使用三氧同位素系统学鉴定磷循环中的代谢和酶途径

• 批准号: 501986846
• 负责人: Privatdozent Dr. Daniel Herwartz
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/501986846?language=en
• 关键词: Identification; metabolic; enzymatic; pathways; phosphorous

Phosphorus (P) is often the limiting nutrient for plant growth. This limitation reduces the production of food and the potential of the terrestrial carbon sink to mitigate global warming. It is essential to understand P-cycling in soils to understand how the bioavailable P-pool is maintained and how ecosystems respond to human intervention. This requires an in-depth understanding of the processes, pathways, timescales and factors that contribute to the availability of P to plants.Analyses of isotopes are frequently used to better understand element cycling, but P is mono-isotopic. Therefore, oxygen isotopes of PO4 are used to identify chemical and physical processes within the phosphorous cycle. Here I suggest to expand this proxy by analyzing 17O/16O ratios of PO4 in addition to the more commonly used 18O/16O. This is beneficial for two principal reasons. 1) Air O2 comprises a negative 17O anomaly inherited from mass independent fractionation effects associated to the formation of ozone. This anomaly can be transferred to PO4 in soils via metabolic consumption of air O2 by organisms. It is well known that the body water of animals comprises a negative 17O anomaly. I expect that this anomaly is transferred to animal feces. Guano based fertilizer, for instance, should thus comprise PO4 with a negative 17O anomaly that can be used as a natural tracer. Similarly, metabolically active microorganisms generate anomalous PO4 as shown in the preliminary dataset. In addition, high temperatures during wildfires facilitate inorganic oxygen isotope exchange between air O2 and plant PO4 providing a tracer to investigate fire sequences. I want to test these applications.2) Phosphorus is such an essential element because organisms use it to synthesize DNA, RNA, ATP and phospholipids. This organic phosphate (Porg) is, however, not bioavailable for plants. It is generally assumed that under P limiting conditions, plants release extracellular enzymes, so called phosphatases, as a strategy to acquire P from organic compounds. As demonstrated in our preliminary dataset, these enzymes induce characteristic triple oxygen isotope effects on to the leaving, now bioavailable, PO4 molecule. This isotopic fingerprint can be used to trace enzyme activity within soils. To do so, the enzymatic fingerprints will be characterized precisely using experimental setups.The triple oxygen isotope approach is a promising tool to identify and quantify various processes within the soil phosphorus cycle. If successful, this approach can also be applied e.g. in the marine environment. This proposal is part of a larger Heisenberg proposal, where I plan to apply these 17O systematics to paleo-applications. For this purpose, it is essential to work out the modern day triple oxygen isotope systematics, which is one major goal of this proposal.

磷（P）通常是植物生长的限制养分。这种限制减少了食物的产生和陆生碳汇的潜力，以减轻全球变暖。必须了解土壤中的p循环，以了解如何维持生物利用的P-pool以及生态系统如何应对人类干预。这需要深入了解有助于P对植物的可用性的过程，途径，时间标准和因素。同位素的Analyses经常用于更好地理解元素循环，但P是单异位的。因此，PO4的氧同位素用于鉴定磷循环中的化学和物理过程。在这里，我建议通过分析更常用的18o/16o之外的PO4的17O/16O比来扩展该代理。这是有益的，原因有两个。 1）空气O2包含由与臭氧形成相关的质量独立分离效应遗传的负17o异常。这种异常可以通过生物体对空气O2的代谢消耗转移到土壤中的PO4。众所周知，动物的体水包括阴性17o异常。我希望这种异常被转移到动物粪便中。因此，基于鸟粪的肥料应构成PO4，具有负17o异常，可以用作天然示踪剂。同样，代谢活性微生物会产生异常的PO4，如初步数据集所示。此外，野火期间的高温有助于空气O2和植物PO4之间的无机氧同位素交换，从而提供了研究火序列的示踪剂。我想测试这些应用。2）磷是如此重要的元素，因为生物体将其用于合成DNA，RNA，ATP和磷脂。但是，这种有机磷酸盐（PORG）对于植物而言并不可生物利用。通常假定在限制条件下，植物释放细胞外酶，即所谓的磷酸酶，是从有机化合物中获取P的一种策略。正如我们的初步数据集所示，这些酶会诱导特征性三重氧同位素对离开（现在可生物利用的PO4分子）的影响。这种同位素指纹可用于追踪土壤中的酶活性。为此，酶促指纹将精确地使用实验设置进行表征。三重氧同位素方法是在土壤磷循环中识别和量化各种过程的有前途的工具。如果成功，也可以应用这种方法，例如在海洋环境中。该提案是更大的海森伯格提案的一部分，我计划将这些17O系统学应用于古申请。为此，必须制定现代三重氧同位素系统学，这是该提案的主要目标之一。