Microbial assimilation of phosphorus in the subtropical Atlantic Ocean: a molecular approach

亚热带大西洋中磷的微生物同化：分子方法

基本信息

批准号：
NE/J013676/1
负责人：
Claire Mahaffey
金额：
$ 6.62万
依托单位：
University of Liverpool
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ013676%2F1
关键词：
Microbial assimilation phosphorus subtropical Atlantic

项目摘要

Phosphorus (P) is an essential element for all living matter on earth, irrespective of size or habitat. Microbes are microscopic organisms that require P to synthesize building blocks for DNA, build cell envelopes and create energy transfer molecules. In the ocean, P exists in three forms; phosphate (PO4), dissolved organic P (DOP) and particulate P (PP). PO4 is the most readily used by marine microbes for growth. In coastal or subpolar regions, PO4 concentrations are sufficiently high to support microbial growth. However, in regions of the ocean called subtropical gyres, surface PO4 concentrations are extremely low and limit microbial growth. Conversely, DOP concentrations are up to 100 times higher than PO4. A diverse array of microbes live in these PO4-limited but DOP-plentiful regions but how do they cope with P-stress? Do microbes compete for the same small pool of PO4 or can they access the complex DOP pool? How do they co-exist? The research proposed here will begin to answer these questions. During a research cruise in the Atlantic Ocean in 2011, we collected samples along a gradient of PO4 and DOP concentration and availability. We propose to examine the presence and expression of genes contained within microbes that encode for the production of proteins that allow microbes to acquire P, i.e. 'P-acquisition genes'. Molecular studies have shown that some genes can produce proteins that bind PO4 at very low concentrations or enzymes that can cleave P bound to organic phosphorus. For example, the PhoA gene encodes for the production of alkaline phosphatase, an enzyme that cleaves P bound to organic molecules called phosphomonoesters that make up 20 to 75% of the DOP pool. Microbes that possess PhoA can therefore access a large part of the DOP pool. We propose to determine the relative distribution of five P-acquisition genes. However, it is possible for a microbe to possess a gene, but for that gene to be switched off. Therefore, we will not only determine the presence of the genes, but also if they are switched on or are being 'expressed'. We will target 3 ecologically important species living in the ocean: Prochlorococcus and Synechococcus, which are microscopic cyanobacterium that are important for cycling of carbon in the ocean, and Trichodesmium, a colony forming cyanobacteria that are visible to the naked eye and play an important role in the marine nitrogen cycle. In summary, we propose to use molecular techniques to determine the presence and expression of 5 P-acquiring genes in 3 ecologically important species along a gradient in P-availability. Why is this important? Subtropical gyres represent 70% of the world's ocean. Observations from the Atlantic and Pacific Oceans show that these vast regions are showing signs of warming in response to climate change through changes in water column stability and microbial community structure. Importantly, it is predicated that climate change will enhance P-limitation in subtropical gyres and thus it is vital that we understand the P-acquisition genes of ecologically important microbes in order to identify the winners and losers in a changing ocean environment.

磷 (P) 是地球上所有生物的必需元素，无论其大小或栖息地如何。微生物是需要磷来合成 DNA 构件、构建细胞包膜和产生能量转移分子的微生物。在海洋中，P以三种形式存在；磷酸盐（PO4）、溶解有机磷（DOP）和颗粒磷（PP）。 PO4 最容易被海洋微生物用于生长。在沿海或亚极地地区，PO4 浓度足以支持微生物生长。然而，在被称为亚热带环流的海洋区域，表面 PO4 浓度极低，限制了微生物的生长。相反，DOP 浓度比 PO4 高 100 倍。各种各样的微生物生活在这些 PO4 有限但 DOP 丰富的区域，但它们如何应对 P 胁迫呢？微生物是否会竞争同一个小 PO4 池，还是可以访问复杂的 DOP 池？它们如何共存？这里提出的研究将开始回答这些问题。在 2011 年大西洋的一次研究航行中，我们沿着 PO4 和 DOP 浓度和可用性的梯度收集了样本。我们建议检查微生物中所含基因的存在和表达，这些基因编码产生允许微生物获取 P 的蛋白质，即“P 获取基因”。分子研究表明，一些基因可以产生在极低浓度下与 PO4 结合的蛋白质，或可以裂解与有机磷结合的 P 的酶。例如，PhoA 基因编码碱性磷酸酶的产生，这种酶可以裂解与称为磷酸单酯的有机分子结合的 P，磷酸单酯占 DOP 库的 20% 至 75%。因此，拥有 PhoA 的微生物可以获取大部分 DOP 库。我们建议确定五个 P 获取基因的相对分布。然而，微生物有可能拥有一个基因，但该基因被关闭。因此，我们不仅要确定基因是否存在，还要确定它们是否已打开或正在“表达”。我们将针对生活在海洋中的 3 种具有重要生态意义的物种：原绿球藻和聚球藻（它们是对海洋碳循环非常重要的微小蓝藻）和毛藻（一种肉眼可见且发挥重要作用的形成蓝藻的菌落）在海洋氮循环中。总之，我们建议使用分子技术来确定 3 个生态重要物种中 5 个磷获取基因沿着磷有效性梯度的存在和表达。为什么这很重要？副热带环流占世界海洋的70%。对大西洋和太平洋的观测表明，这些广阔的地区通过水体稳定性和微生物群落结构的变化，显示出因气候变化而变暖的迹象。重要的是，据预测气候变化将增强副热带环流的磷限制，因此我们了解具有重要生态意义的微生物的磷获取基因至关重要，以便确定不断变化的海洋环境中的赢家和输家。