The Oceanography of B-Vitamins: evaluating how nutrients and trace metals influence their synthesis, cycling, and biogeochemical impact

众所周知，b族维生素是参与大量代谢途径的重要生长因子。然而，迄今为止，关于这些生长因子在调节海洋系统生物活动方面的重要性所做的工作很少。基因组数据表明，海洋系统中b族维生素的供应主要依赖于原核生物的生物合成。相比之下，目前测试的真核浮游植物中有一半已被确定对至少一种维生素缺乏营养。因此，缺乏来自原核细胞的外源这些生长因子可能会严重影响所谓的生物泵的效率，这是由大型真核细胞主导的。在这个项目中，南加州大学的研究人员将首次深入评估海洋中最重要的生长因子之一b族维生素（B1、B7和B12）的来源和循环。这将通过在三个不同的海洋学体系(南加州的圣佩德罗海洋时间序列站点（spot），夏威夷海洋时间序列站点（HOT） ALOHA，以及前往东热带南太平洋（ETSP）的机会巡航和不同海洋原核物种培养的实验室操作实验来完成。实地研究地点的选择是为了提供关于维生素在广泛的海洋环境中循环的最大数量的信息。根据初步研究结果，研究小组提出了以下假设：(1)海洋中存在几种潜在的b族维生素的产生菌：世界海洋中上层的非重氮营养蓝藻和异养细菌，并且世界海洋亚热带-热带LNLC区域的重氮营养蓝藻进一步增加了b族维生素的可得性；(2)某些b族维生素的合成受特定溶解微量金属如Co（用于B12）和Fe（用于B2和B7）以及有机和无机营养物质的有效性控制；(3) B族维生素的产生（在颗粒相中发现）和释放（在溶解相中发现）之间的平衡决定了维生素的可用性和环境循环，而这种平衡是由三个因素决定的：微型和微型浮游生物的活动、物理运输和营养不良浮游生物的吸收。为了验证这些假设，他们开发了一种新方法，使用三重四极杆质谱仪与液相色谱仪相结合，使他们能够在不到一升的海水中，以及在细胞内和颗粒池中，同时直接测量所有b族维生素。更广泛的影响：该项目的科学和社会影响包括阐明b族维生素的循环，没有它，我们将永远无法完全了解维持主要生物过程所需的所有必需物质，如初级生产和海洋中的固氮。研究生和本科生都将参与这个项目。主要研究人员是COSEE-West项目的积极参与者，该项目由海洋科学家、K-12教育工作者和公众组成。

It is well known that the B-vitamins are important growth factors involved in a large number of metabolic pathways. However, to date, very little work has been done regarding the importance of those growth factors in regulating biological activity in marine systems. Genomic data indicates that the supply of B-vitamins in marine systems depends mainly on biosynthesis by prokaryotes. In contrast, half of the currently tested eukaryotic phytoplankton have been determined to be auxotrophic for at least one vitamin. Therefore, the lack of an exogenous source of these growth factors from prokaryotic cells may strongly impact the efficiency of the so-called biological pump, which is dominated by large eukaryotic cells. In this project, researchers at the University of Southern California will carry out the first in-depth evaluation of the sources and cycling of arguably one of the most important growth factors in the ocean, the B-vitamins (B1, B7, and B12). This will be accomplished by combining field studies in three different oceanographic regimes (San Pedro Ocean Time Series site (SPOTS) off Southern California, The Hawaii Ocean Time-Series (HOT) station ALOHA, and a cruise of opportunity to the East Tropical South Pacific (ETSP) with lab manipulation experiments of cultures of different marine prokaryotic species. The field study sites are selected to give the maximum amount of information about the cycling of vitamins in a broad range of marine environments. Based on preliminary results, the research team hypothesizes: (1) that there are several potential producers of B-vitamins in the ocean: non-diazotrophic cyanobacteria and heterotrophic bacteria in the upper euphotic zone of the world ocean, and that the availability of B-vitamins is further augmented by diazotrophic cyanobacteria in subtropical-tropical LNLC regions of the world ocean; (2) that the synthesis of some B-vitamins is controlled by the availability of specific dissolved trace metals such as Co (for B12) and Fe (for B2 and B7) and organic and inorganic nutrients; and (3) that the balance between B vitamin production (found in the particulate phase) and release (found in the dissolved phase) dictates vitamin availability and environmental cycling, and that this balance is set by three factors: the activity of a subset of the pico and microplankton, physical transport, and uptake by auxotrophic plankton. In order to test these hypotheses, they developed a new method, using a triple quadrupole mass spectrometer coupled to a liquid chromatographer, which allows them to measure directly all B-vitamins simultaneously in less than a liter of seawater as well as in the intracellular and particulate pools. Broader impacts: The scientific and societal impacts of this project include elucidating the cycling of B-vitamins, without which we will never have a complete understanding of all of the essential substances needed to sustain major biological processes such as primary production and nitrogen fixation in the ocean. Both graduate and undergraduate students will participate in this project. The principal investigators are active participants in the COSEE-West program, which involves a network of marine scientists, K-12 educators, and the general public.