Phosphonate Utilization by Eukaryotic Phytoplankton: Who, How, and Where?

磷是所有活细胞所必需的营养物质。它是遗传物质和细胞膜的中心成分，是能量生产和调节酶活性的组成部分。在海洋环境中，磷以无机(PI)和溶解有机(DOP)的形式存在，这两种不同形态的磷的有效性和浓度是控制海洋浮游植物生长的重要因素。海洋浮游植物是单细胞光合作用生物，既可以是原核细菌，也可以是真核植物。虽然磷是海洋浮游植物的首选磷形式，但在海洋的大片区域，磷的水平如此之低，以至于限制了浮游植物的生长。在这些地区，DOP是最重要的磷来源。DOP池的组成一般可分为两大类：对苯酯和磷酸盐。所有海洋浮游植物都能够利用磷酯来支持生长；相比之下，迄今为止，磷酸盐只被证明是细菌营养中磷的重要来源。该项目将确定海洋真核浮游植物利用磷酸盐作为磷来源进行生长的能力。基因组分析将确定真核浮游植物物种对磷酸盐生长的代谢反应，以及自然种群使用磷酸盐的相关性。了解控制海洋营养物质循环的浮游植物的代谢能力是至关重要的。此外，该项目对于了解海洋变化对浮游植物生长的潜在影响具有重要价值。该项目支持为当地社区大学的本科生提供研究机会，以及为服务于不同学生群体的课外项目提供实践丰富的项目。磷酸盐占海洋DOP库的10%，已被证明是一个动态的P库，被海洋光合作用细菌吸收和产生。真核浮游植物用磷酸盐补充其生长的能力仍未得到很大的探索。几种真核浮游植物已被证明使用草甘膦作为磷源，草甘膦是一种化学合成的除草剂磷酸盐；目前尚不清楚远洋真核浮游植物是否可以利用海洋环境中自然存在的磷酸盐。初步实验表明，至少有一些真核浮游植物能够直接利用胞外磷酸盐。该项目描述了磷酸盐在真核浮游植物谱系中的普遍应用，并确定了支持自然产生的磷酸盐的获取和生长的细胞基础。除了系统发育分析外，该项目还使用全细胞转录组分和功能基因互补分析，以了解磷酸盐的生物利用度和天然真核浮游植物种群利用磷酸盐的相关性。了解控制海洋生物地球化学循环的浮游植物的代谢能力是至关重要的。考虑到未来海洋可能变得更加分层的预测，这一点尤其重要，这可能会增加DOP，包括磷酸盐，在支持浮游植物生长方面的重要性。

Phosphorus (P) is an essential nutrient for all living cells. It is a central component of genetic material and cellular membranes and is integral to energy production and regulating enzyme activity. In the marine environment, P occurs as inorganic (Pi) and dissolved organic (DOP) forms; the availability and concentration of these different forms of P is an important control on marine phytoplankton growth. Marine phytoplankton are single-celled photosynthetic organisms and can be both prokaryotic bacteria and eukaryotic plants. While Pi is the preferred form of P for marine phytoplankton, in large regions of the oceans it is at such low levels that it restricts phytoplankton growth. In these regions, DOP is the most important P source. The composition of the DOP pool can generally be divided into two major groups: P esters and phosphonates. All marine phytoplankton are capable of using P esters to support growth; in contrast, phosphonates have only been shown to be an important source of P in the nutrition of bacteria to date. This project will determine the ability of marine eukaryotic phytoplankton to use phosphonates as a source of P for growth. Genomic analyses will determine the metabolic response of eukaryotic phytoplankton species to growth on phosphonates as well as the relevance of phosphonate use by natural populations. It is critical to understand the metabolic capabilities of phytoplankton which control marine nutrient cycling. In addition, the project is of great value in understanding the potential impacts of a changing ocean on phytoplankton growth. The project supports reseach opportunities for undergraduates from a local community college as well as hands-on enrichment programs for an afterschool program that serves a diverse student population. Comprising up to 10% of the marine DOP pool, phosphonates have been shown to be a dynamic P pool both being assimilated and produced by marine photosynthetic bacteria. The ability of eukaryotic phytoplankton to supplement their growth with phosphonates remains vastly unexplored. Several eukaryotic phytoplankton species have been shown to use glyphosate, a chemically synthesized herbicidal phosphonate, as a P source; it remains unknown if open ocean eukaryotic phytoplankton can utilize phosphonates found naturally in the marine environment. Preliminary experiments suggest at least some eukaryotic phytoplankton are able to directly utilize extracellular phosphonates. This project characterizes the pervasiveness of phosphonate utilization within eukaryotic phytoplankton lineages and identifies the cellular underpinnings that support the acquisition of and growth on naturally occuring phosphonates. The project uses whole-cell transcriptomics and functional gene complementation assays, in addition to phylogenetic analyses, to understand the bioavailability of phosphonates and relevance of phosphonate utilization by natural eukaryotic phytoplankton populations. It is critical to understand the metabolic capabilities of phytoplankton which control marine biogeochemical cycles. This is especially important given the prediction that future oceans may become more stratified which could increase the importance of DOP, including phosphonates, in supporting phytoplankton growth.