ROW: Dissolved Organic Nitrogen Uptake by Autotrophic Plankton Studied with Flow Cytometry

小行星9416634 溶解有机氮（DON）库是海洋氮循环的一个动态组成部分。 尽管DON可以代表海洋系统中最大的固定氮库，但由于缺乏合适的方法，有关其利用的信息很大程度上仅限于氨基酸或尿素等少数有机化合物。 尽管缺乏对大部分未定义的DON池的利用的知识，但细菌被认为是海洋系统中DON的主要用户（尿素除外）。 然而，浮游植物酶学的最新研究表明，这一假设需要重新评估。 一些浮游植物的细胞表面氧化酶，使他们能够从氨基酸，伯胺，和潜在的其他有机化合物裂解氨基。 已知的浮游植物，这些氧化酶是较小的自养生物，可以潜在地包括在“细菌”的大小部分在传统的大小分级实验。 这个行规划赠款项目将结合联合收割机的流式细胞术和新开发的15 N示踪技术的强大工具，区分自养从异养吸收的DON。 这项计划资助的目标是（1）改进现有的细胞分选技术，用于分离足够大数量的自养生物和异养生物，以允许测量15N原子%富集，从而允许测量自养生物的DON摄取速率，获得热带北太平洋东部自养生物吸收DON的初步数据，用于支持NSF的全面建议。 ***

9416634 Bronk The dissolved organic nitrogen (DON) pool is emerging as a dynamic component of marine nitrogen cycles. Though DON can represent the largest pool of fixed nitrogen in marine systems, the lack of suitable methods has kept information on its utilization largely limited to a few individual organic compounds such as amino acids or urea. Despite the lack of knowledge on utilization of the bulk of the undefined DON pool, bacteria are considered the primary users of DON in marine systems (with the exception of urea). Recent work in phytoplankton enzymology, however, suggests this assumption needs to be reevaluated. Some phytoplankton are now known to posses cell surface oxidases which allow them to cleave amino groups from amino acids, primary amines, and potentially other organic compounds. The phytoplankton known to posses these oxidases are smaller autotrophs which could potentially be included in the "bacterial" size fraction in traditional size fractionation experiments. This Row Planning Grant project will combine the powerful tools of flow cytometry and newly developed 15N tracer techniques to discriminate autotrophic from heterotrophic uptake of DON. The objectives of this Planning Grant are to (1) refine existing cell sorting techniques for separating autotrophs from heterotrophs in large enough numbers to allow the measurement of 15N atom % enrichments and thus allow the measurement of DON uptake rates by autotrophs, and (2) to obtain preliminary data on uptake of DON by autotrophs in the Eastern Tropical North Pacific to be used in support of a full scale NSF proposal. ***