Regulation of polyphosphate metabolism in Chlamydomonas and potential for exploitation as P phosphorus sink in nutrient recovery systems

磷是生命所必需的元素。它是我们遗传信息（DNA和RNA）的一个组成部分。它在我们新陈代谢的许多方面起着至关重要的作用，包括我们细胞的主要能量货币ATP。它是包围我们细胞的细胞膜的一个组成部分。它不能代替任何其他元素。我们从饮食中以磷酸盐的形式获得磷（磷与四个氧原子结合）。磷通过植物从土壤中获取磷酸盐进入食物链。植物，像所有形式的生命一样需要这种元素，正如任何园丁所知道的，它是植物生长的重要常量营养元素之一——氮磷钾肥料中的磷。虽然磷是一种相当丰富的元素，但环境中的大部分磷并不是植物可以轻易利用的形式（即可溶性磷酸盐）。大部分磷被锁在土壤中的有机物中，或者被束缚在土壤颗粒的表面。这就是为什么园艺师和农民使用含磷肥料来获得良好的作物产量。然而，这里有一个双重问题。为了满足目前的需要，人们将磷酸盐岩加工成磷肥，但这种不可再生资源正在被利用，而不是被取代。按照目前的使用速度，我们将在50到200年之间耗尽，所以如果我们想养活我们的孩子的孩子，一切照旧是不可能的。另一个问题更为紧迫；我们使用的很多磷都被浪费了。其中一些作为农业径流进入河道，并可能导致河流和湖泊中的藻类大量繁殖。其中大部分最终以尿液、粪便、有机废物和洗涤剂的生活废水形式进入污水处理厂。由于严格的水质环境法规，去除不需要的磷是必要的，也是昂贵的，这导致了高昂的水费。使用化学物质沉淀磷是一种常用的方法，但限制了作为肥料的再利用。生物方法也被使用，这是目前研究的一个活跃领域，但到目前为止，还没有一个真正解决了以经济和可重复使用的方式回收磷的问题。这个提议是为了研究一种叫做衣藻的藻类的基本机制，衣藻是一种微小的单细胞光合生物，它吸收和储存磷酸盐。衣藻天然存在于英国，利用废水中的有机化合物或光提供能量，在废水中生长良好。它可以将磷酸盐积累到潜在的高水平，但其机制尚不完全清楚。为了能够使用衣藻或其他自然产生的藻类来有效地清理废水，并回收再生的磷酸盐作为肥料，我们需要了解这些机制是什么，以及它们是如何以及何时运作的。我们项目的目的是1)观察被认为参与磷酸盐积累和储存的基因表达变化的影响，以了解它们在这一过程中的作用和重要性；2)验证关于一个目前未知功能的基因的功能假设，该基因的突变表型与磷酸盐代谢有关；3)通过寻找过度积累磷酸盐的突变体来发现哪些基因是重要的。这些基础知识将帮助工程师设计低成本、低碳和环保的系统，用于污水处理厂的磷酸盐回收，以实现农业的可持续再利用。

Phosphorus is an essential element for life. It is a component of our genetic information (DNA and RNA). It plays critical roles in many aspects of our metabolism including the major energy currency of our cells ATP. It is a component of the membranes which surround our cells. It cannot be substituted for any other element. We obtain our phosphorus from our diet in the form of phosphate (phosphorus bonded to four oxygen atoms). Phosphorus enters the food chain through the acquisition of phosphate from the soil by plants. Plants, like all forms of life require this element and as any gardener knows it is one of the important macronutrients for plant growth- the P in your NPK fertiliser. Although it is quite an abundant element, most of the phosphorus in the environment is not in a form that plants can readily make use of (i.e., as soluble phosphate). Much of the phosphorus is locked in organic matter in the soil or bound to the surface of soil particles. This is why to get a good crop yield gardeners and farmers apply phosphate containing fertiliser. However there is a two-fold problem. To meet current needs rock phosphate is processed into phosphate fertiliser, but this non-renewable resource is being used and not replaced. At current rates of usage we will run out in between 50 and 200 years, so business as usual is not an option if we want to feed our children's children. The other problem is a more immediate one; much of the phosphorus we do use is wasted. Some of it enters water courses as agricultural run-off and can cause algal blooms in rivers and lakes. Much of it ends up at sewage works in domestic waste water from urine, faeces, organic waste and detergents. Because of strict environmental regulations on water quality, removing the unwanted phosphorus is necessary and expensive, contributing to high water bills. Use of chemicals to precipitate the phosphorus is a common method but limits reuse as a fertiliser. Biological methods are also used, and this is an active area of current research, but so far none have truly solved the problem of recovering phosphorus in an economic and re-usable way. This proposal is to investigate the fundamental mechanisms by which a species of alga called chlamydomonas, a microscopic unicellular photosynthetic organism, take up and store phosphate. Chlamydomonas is naturally occurring in the UK and grows well on waste water using either organic compounds in the waste, or light, to provide energy. It can accumulate phosphate to potentially high levels but the mechanisms by which it does so are not fully understood. To be able to use chlamydomonas or other naturally occurring algae to clear up waste water efficiently and recycle the reclaimed phosphate as fertiliser we need to understand what these mechanisms are and how and when they operate. The aims of our project are 1) to look at the effect of changing expression of genes that are thought to be involved in phosphate accumulation and storage to understand their role and importance in this process; 2) to test an hypothesis about the function of a gene of currently unknown function whose mutant phenotype implicates it in phosphate metabolism and 3) to find out which genes are important by looking for mutants which hyper accumulate phosphate. This fundamental knowledge will help engineers to design low-cost, low-carbon and environmentally friendly systems for phosphate recovery at sewage treatment works for sustainable reuse in agriculture.