Heme uptake by marine bacteria: A molecular-level study of an oceanic iron recycling pathway

了解海洋微生物对营养物质的同化机制对海洋科学非常重要，特别是对微量营养元素铁（Fe）而言，它在海洋表层水中的浓度通常是有限的。海水中的大部分铁与有机配体络合，最近的研究已经检验了海洋细菌吸收这些不同形式铁的能力。铁的一个潜在来源是通过血红素的同化，这是一种含铁的生化物质，最近已经表明海洋细菌具有血红素摄取的运输系统。因此，本项目旨在研究铁是否被吸收为血红素，以及这是否是海洋微生物积累铁的重要途径。血红素摄取的潜力将在实验室培养研究中进行检验。遗传工具和操作将用于确定摄取机制，证明其活性，并表明这是否是一个重要的同化途径。这些方法也将用于检查这一途径在天然海洋微生物群落中的程度。该提案将把其活动与美国国家科学基金会资助的加州海洋科学教育卓越中心（COSEE CA）和斯克里普斯教育联盟结合起来，将研究影响扩展到K-12公共教育。通过与圣地亚哥大学城高中教师的互动，已经建立了教师研究经验关系。这项研究还将支持一名研究生的博士论文，该研究生的博士论文将以这项研究为重点。本研究的科学广泛影响涉及了解铁的海洋生物地球化学和化学-生物联系，以及限制营养物质对海洋全球生物地球化学的作用。

Understanding the mechanisms of assimilation of nutrients by marine microorganisms is important to marine science, especially for the micronutrient iron (Fe), which is often present in limiting concentrations in marine surface waters. Much of the Fe is ocean water is complexed to organic ligands and recent studies have examined the capabilities of marine bacteria to assimilate these different forms of Fe. One potential source of Fe is through the assimilation of heme, a Fe-containing biochemical, and it has been recently shown that marine bacteria have transport systems for heme uptake. This project is therefore aimed at examining if Fe is assimilated as heme and whether this is an important pathway for iron accumulation by marine microorganisms. The potential for heme uptake will be examined in laboratory culture studies. Genetic tools and manipulations will be used to identify the uptake mechanisms, demonstrate their activity and show whether this is an important assimilation pathway. These approaches will also be used to examine the extent of this pathway in natural marine microbial communities.This proposal will integrate its activities with the NSF-funded Center for Ocean Science Education Excellence - California (COSEE CA) and with Scripps Educational Alliances to extend the research impact to K-12 public education. A Research Experiences for Teachers relationship has already been established through these interactions with teachers at University City High School in San Diego. This research will also support for a graduate student whose PhD thesis will focus on this research. The scientific broader impacts of this research relate to understanding the ocean biogeochemistry of Fe and the chemical-biological linkages, and the role of limiting nutrients on the global biogeochemistry of the ocean.