Discovering novel microbial tools to mitigate the global phosphorus crisis: Identification of unique phosphatases in abundant rhizobacteria

面对气候变化和自然资源枯竭等几个新出现的全球问题，需要为不断增加的全球人口提供足够的粮食，因此迫切需要探索产生可持续农业做法的新方法。例如，目前，农业在很大程度上依赖于密集使用矿砂磷肥来维持足够的作物产量。不幸的是，预测表明，在接下来的50-200年内，我们可能会用完只能通过地质过程生产的磷矿。此外，只有10%-30%的磷矿粉作为肥料被植物吸收用于生长。这种低效会导致富营养化等问题，这对我们的环境和野生动物都有负面影响。大多数土壤实际上被多种形式的无机和有机磷(OP)饱和，不幸的是，如果不事先转化为一种有效的形式，正磷酸盐，植物就无法获得这些磷。植物动员锁定在这些不同形式中的磷的能力有限。因此，植物在很大程度上依赖于它们与各种微生物的结合来帮助它们从各种复杂的无机和有机形式中获得可生物利用的正磷酸盐。土壤有机磷复合体转化为正磷酸盐的主要微生物机制之一是胞外磷酸酶的产生。尽管在了解微生物在动员土壤有机质中的作用方面取得了进展，但对这一过程的完整和整体的理解仍然未知。因此，我们利用微生物作为减轻对磷矿依赖的能力是不够的。我最近发现，生活在英国第三大经济作物油菜根际的一群与黄杆菌属有关的丰富细菌显示出强大的结构性磷酸酶活性。这种表型似乎既是黄杆菌所特有的，也是对植物有潜在益处的。然而，负责这种有趣和独特的表型的特定酶仍不清楚。拟杆菌门(主要是黄杆菌)可占植物微生物群的65%，是人类和海洋微生物群的主要组成部分。因此，它们可能在调节环境磷动态方面起着重要作用。因此，该项目的主要目的是鉴定和描述由这些未被研究但有趣的黄杆菌产生的新的未鉴定的磷酸酶。该项目的两个主要成果是：1)发现了具有潜在农业技术应用的新型微生物酶；2)发现了土壤有机质循环中的新成分。这两项成果都将提高我们对全球磷循环和可持续农业实践的了解，通过提高植物利用锁定在土壤中的天然磷资源的效率。我将以Tim Daniell教授的实验室为东道主，在谢菲尔德大学动植物科学系担任这一研究员。Daniell实验室位于最先进的Arthur Willis环境中心，这里是植物保护和生产(P3)中心的所在地，该中心统一了不同的植物和土壤科学家。谢菲尔德大学在英国的卓越研究排名前10%(2014年卓越研究框架)，谢菲尔德大学99%的研究在国际上得到认可，其中48%的生物科学研究被归类为4*世界领先。因此，在谢菲尔德获得这一享有盛誉的奖学金将为我提供最好的机会，开始在学术界的职业生涯，解决与粮食安全相关的新问题。

The demand to provide sufficient food for a rising global population in the face of several emerging global issues, such as climate change and depletion of natural resources, has resulted in an urgent need to explore novel ways of generating sustainable agricultural practices. For example, currently, agriculture massively relies on the intensive application of rock phosphate fertiliser to maintain sufficient crop yields. Unfortunately, predictions suggest that we could run out of rock phosphate, which is only produced through geological processes, within the next 50-200 years. In addition, only 10-30% of rock phosphate, applied as fertiliser, is taken up by the plant for growth. This inefficiency leads to problems such as eutrophication, which has negative effects on our environment and wildlife. Most soils are actually saturated with numerous forms of inorganic and organic phosphorus (oP) that are unfortunately unavailable to plants without prior transformation to an available form, orthophosphate. Plants have a limited ability to mobilise phosphorus locked up in these various forms. Therefore, plants heavily rely on their associations with various microorganisms to assist them in acquiring bioavailable orthophosphate from various complex inorganic and organic forms. One of the major microbial mechanisms involved in transforming various soil oP complexes into orthophosphate is the production of extracellular phosphatases. Despite advances in understanding the role of microorganisms in mobilising soil oP, a complete and holistic understanding of this process remains unknown. Therefore, our ability to use microorganisms as a means of alleviating our reliance on rock phosphate is inadequate.I recently discovered that a group of abundant bacteria related to the genus Flavobacterium, that inhabit the rhizosphere of Oil Seed Rape, the UK's 3rd most economically important crop, exhibited both strong and constitutive phosphatase activity. This phenotype appears to be both unique to Flavobacterium and potentially beneficial for plants. However, the specific enzymes responsible for this interesting and unique phenotype remain unknown. The phylum Bacteroidetes (predominantly Flavobacteria), can constitute up to 65% of the plant microbiome and are major components of the human and marine microbiomes. Therefore, they likely have a major role in regulating environmental phosphorus dynamics. The major aim of this project is to therefore identify and characterise the novel unidentified phosphatases produced by these under-studied but interesting Flavobacteria. The two major outcomes of this project are 1) the discovery of novel microbial enzymes with potential agritech application 2) the discovery of new components in the soil oP cycle. Both of these outcomes will improve our knowledge regarding the global phosphorus cycle and sustainable agricultural practices, through increasing the efficiency by which plants utilise natural phosphorus resources locked up in soils.I will undertake this Fellowship in the Department of Animal and Plant Sciences at the University of Sheffield using the lab of Prof. Tim Daniell as a host. The Daniell lab is based in the state-of-the-art Arthur Willis Environmental Centre, home of the Plant Protection and Production (P3) Centre, which unifies a diverse set of plant and soil scientists. The University of Sheffield was placed in the top 10% of research excellence in the UK (2014 Research Excellence Framework) and 99% of research at Sheffield that is internationally recognised with 48% of research in Biological Sciences classed as 4* world leading. Therefore, undertaking this prestigious Fellowship at Sheffield will provide me with the best opportunities to embark on a career in academia and tackle the emerging issues related to food security.