Collaborative Research: The Impact of Pelagibacter on DOM Composition Under Light and Dark Conditions

异养细菌代谢和光化学降解是海洋环境中溶解性有机物（DOM）的两种主要转化机制。 在这项研究中，来自伍兹霍尔海洋研究所、俄勒冈州州立大学和马里兰州大学的科学家们将通过比较受光照或单一细菌物种影响的DOM的单个化合物的使用来解决这两个问题。 普适Pelagibacter ubique是一种普遍存在的海洋细菌，占海洋异养细菌总数的25%。 虽然P. ubique已经被分离到实验室培养物中，并且其基因组已经被测序，但是这种重要的海洋细菌的生长需求没有得到很好的限制，尽管P. ubique生长的营养限制没有通过添加无机或有机补充物来减轻。 科学家们将建立在他们的初步工作基础上，表明P. ubique在光照条件下生长时会结合并产生不同的化合物，而不是在黑暗条件下生长，这是令人惊讶的，因为P. ubique在光照和黑暗条件下没有生长差异，尽管存在Proteorhodopsin质子泵。研究人员将研究光化学对P. ubique在生长实验中结合和产生的化合物的影响，通过傅里叶变换离子回旋共振质谱（FTICR-MS）确定DOM的分子水平组成及其与P. ubique孵育前后的光学特性。 在有光和无光的情况下确定泛藻的生长底物将是限制海洋系统中异养活动可能底物的重要一步，这项工作的一个重要组成部分将是继续开发FTICR-MS数据的分析框架。首先，他们将进一步开发内标和新的光谱对齐算法。其次，它们将增强现有的自动化分析工具，包括有关化合物结构和组成的辅助信息，如液相色谱的极性预测和MS/MS实验的碎片光谱。他们的目标是提供一个数据分析管道，包括自动校准，光谱对齐，强大的光谱比较和元素公式分配。 这项研究的更广泛的影响之一是开发了一个分析框架，用于对FT-ICR MS数据进行稳健和常规检查，这对该技术在地球化学中的应用至关重要。 研究人员将在WHOI，UMD和OSU培训FTICR MS的研究生，并将为其他机构的研究生提供旅行资金，以便将他们的方法传播给更广泛的地球科学界。

Heterotrophic bacterial metabolism and photochemical degradation are two of the primary transformative mechanisms for dissolved organic matter (DOM) in the marine environment. In this research, scientists from Woods Hole Oceanographic Institution, Oregon State University and University of Maryland will attack both issues by comparing use of individual compounds of DOM affected by light or by a single bacterial species. Pelagibacter ubique is a ubiquitous marine bacterial species and can represent up to 25% of the heterotrophic bacterial population in the ocean. Although P. ubique has been isolated into laboratory culture and its genome has been sequenced, the growth requirements of this important marine bacterium are not well constrained, although nutrient limitation of P. ubique growth is not alleviated by the addition of inorganic or organic supplements. The scientists will build on their preliminary work that indicates that P. ubique incorporates and produces different compounds when grown under light conditions than under dark conditions, which is surprising since P. ubique exhibits no growth differences under light and dark conditions, despite the presence of a proteorhodopsin proton pump. The researchers will investigate the impact of photochemistry on the suite of compounds incorporated and produced by P. ubique during growth experiments, determining the molecular-level composition of DOM by Fourier Transform Ion Cyclotron Resonance Mass Spectroscopy (FTICR-MS) and its optical characteristics before and after incubation with P. ubique. Identification of growth substrates of P. ubique in the presence and absence of light will be an important step forward in constraining possible substrates for heterotrophic activity in marine systems.An important component of this work will be the continued development of an analytical framework for FTICR-MS data. First, they will further develop work with internal standards and novel spectral alignment algorithms. Second, they will enhance existing automated analytical tools to include ancillary information regarding compound structure and composition such as polarity predictions from liquid chromatography and fragmentation spectra from MS/MS experiments. Their goal is to provide a data analysis pipeline that includes automated calibration, spectral alignment, robust spectral comparisons and elemental formula assignments. Among the broader impacts of this research is the development of an analytical framework for robust and routine examination of FT-ICR MS data that is critical for the applications of this technique to biogeochemistry. The researchers will train graduate students at WHOI, UMD and OSU in FTICR MS and will provide travel funds to graduate students from other institutions in order to disseminate their approach to the broader geosciences community.