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的工作很少。基因组数据表明，海洋系统中维生素B的供应主要取决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被确定为至少一种维生素营养缺陷型。因此，缺乏来自原核细胞的这些生长因子的外源性来源可能会强烈影响所谓的生物泵的效率，生物泵由大型真核细胞主导。在这个项目中，南加州大学的研究人员将对海洋中最重要的生长因子之一B族维生素（B1，B7和B12）的来源和循环进行首次深入评估。 这将通过在三个不同的海洋学制度（圣佩德罗海洋时间序列网站（SPOTS）关闭南加州，夏威夷海洋时间序列（HOT）站ALOHA，并与不同的海洋原核物种的培养实验室操作实验的机会，东热带南太平洋（ETSP）巡航相结合的实地研究来完成。选择实地研究地点是为了提供有关维生素在广泛的海洋环境中循环的最大信息量。根据初步结果，研究小组假设：（1）海洋中存在几种潜在的B族维生素生产者：世界海洋上层真光层的非重氮蓝藻和异养细菌，并且世界海洋亚热带-热带LNLC区域的重氮蓝藻进一步增加了B族维生素的可用性;（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）的可用性控制（B2和B7）以及有机和无机营养素;和（3）B族维生素生产之间的平衡（在颗粒相中发现）和释放（存在于溶解相中）决定了维生素的可用性和环境循环，这种平衡由三个因素决定：皮科和微型浮游生物的一个子集的活动，物理运输和营养缺陷型浮游生物的吸收。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耦合，这使他们能够在不到一升的海水以及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基本物质，如海洋中的初级生产和固氮。 研究生和本科生都将参加这个项目。 主要研究人员是COSEE-West计划的积极参与者，该计划涉及海洋科学家，K-12教育工作者和公众的网络。

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.