Collaborative Research: Vibrio as a model microbe for opportunistic heterotrophic response to Saharan dust deposition events in marine waters

概述：粉尘和矿物气溶胶是海洋表层水微量和宏量营养素的重要来源。越来越多的证据表明，异养微生物可能在处理沉积的矿物质和营养物质方面发挥关键作用。然而，尚不清楚灰尘的哪些成分刺激了异养细菌，哪些细胞机制负责利用这些成分，以及这些细菌的活性如何影响海洋自养生物对灰尘产生的矿物质和营养物质的可得性和利用。了解这些因素对于理解沙尘沉积如何影响碳循环以及预测热带海洋对未来沙尘沉积事件频率和强度变化的响应至关重要。该项目的目的是在受控条件下研究风沙对热带海洋系统中异养微生物的具体影响。中心假设是，在少营养热带系统中，数值较小的机会性细菌是对尘埃成分流入的第一反应者，主要通过迅速获取可溶微量金属和限制撒哈拉尘埃沉积的营养物质来作出反应。该项目将侧重于两个具体目标：1)量化暴露于粉尘后海洋微生物种群的群落结构、组成和转录活性的变化；2)确定撒哈拉沙尘气溶胶中刺激或抑制弧菌生长和/或活性的关键成分，弧菌是一种典型的机会性海洋异养群体。该研究将使用一系列对照实验，旨在通过宏基因组学、转录组学以及大气和海洋生物地球化学技术，利用自然群落和模式细菌（弧菌）识别和量化异养微生物对粉尘沉积事件的反应。这种创新的方法将确定微生物群落中最关键的（反应性）成分，并阐明潜在的反应机制。知识价值：鉴于粉尘气溶胶对生物地球化学循环的潜在巨大影响，人们对其生物反应非常感兴趣，但相对较少的工作已经解决了响应机制（特别是在异养微生物部分中）或确定粉尘气溶胶特定成分的相对重要性。微生物反应的详细框架（侧重于机会性异养）将有助于将自养和异养处理联系起来。这一贡献意义重大，因为它将为海洋生物对沙漠尘埃气溶胶的反应提供首个端到端（从化学到生理学到生态学）机制途径之一。更广泛的影响：这项研究的结果将提供关于气候变化的一个经常被忽视的组成部分的信息，即荒漠化的长期影响，它可能影响整个海洋的生物地球化学循环。此外，以弧菌为模型的工作将有共同的好处，即解决粉尘沉积在海洋传染病全球上升中的可能作用。此外，该项目将为研究生、本科生和高中生提供培训和积极参与研究的机会。所有学生都有机会在地方和区域会议以及国家（国际）会议上展示他们的作品。通过每个机构正在进行的项目，来自STEM弱势群体的学生将被招募，以获得研究机会（以及进入研究生课程）。此外，通过参加乔治亚州海岸研究委员会，这项工作的结果以及海洋科学和气候变化的相关问题将通过会议、链接到GRGC网站和列表服务以及有针对性的出版物，广泛传播给决策者和当地（沿海）利益相关者。

Overview: Dust and mineral aerosols are a significant source of micro and macronutrients to oligotrophic ocean surface waters. Evidence is growing that heterotrophic microbes may play key roles in processing deposited minerals and nutrients. Yet it is not known which components of dust stimulate the heterotrophic bacteria, which cellular mechanisms are responsible for the utilization of those components and how the activity of these bacteria affect the availability and utilization of dust-derived minerals and nutrients by marine autotrophs. Knowledge of these factors is key to understanding how dust deposition impacts carbon cycles and for predicting the response of tropical oceans to future changes in the frequency and intensity of dust deposition events. The objective of this project is to examine the specific effects of aeolian dust on heterotrophic microbes in a tropical marine system under controlled conditions. The central hypothesis is that in oligotrophic tropical systems numerically minor opportunistic bacteria are the first responders to influx of dust constituents and respond primarily by rapidly accessing soluble trace metals and limiting nutrients that are deposited with Saharan dust. The project will focus on two specific aims: 1) Quantify changes in community structure, composition and transcriptional activity among marine microbial populations upon exposure to dust, and 2) Identify key components in Saharan dust aerosols that stimulate or repress growth and/or activity in Vibrio, a model opportunistic marine heterotrophic group. The study will use a series of controlled experiments designed to identify and quantify heterotrophic microbial response to dust deposition events using both natural communities and model bacteria (Vibrio) through metagenomics, transcriptomics and atmospheric and marine biogeochemical techniques. This innovative approach will identify the most critical (reactive) components leached from dust aerosols on the microbial community as well as elucidate potential mechanisms of response.Intellectual Merit: There is great interest in the biological response to dust aerosols given its potentially large influence on biogeochemical cycling, but there has been relatively little work that has addressed the mechanisms of response (especially among the heterotrophic microbial fraction) or identified the relative importance of specific constituents of dust aerosols. A detailed framework for microbial response (focusing on opportunistic heterotrophs) will facilitate efforts to link autotrophic and heterotrophic processing. This contribution is significant because it will provide one of the first end-to-end (chemistry to physiology to ecology) mechanistic pathways for marine biological response to desert dust aerosols.Broader Impacts: The outcomes of this research will provide information on an often overlooked component of climate change, the long range effects of desertification, which could impact biogeochemical cycling throughout the oceans. Furthermore, working with Vibrio as a model will have the co-benefit of addressing the possible role of dust deposition on the global rise of a marine infectious agent. Additionally, this project will provide graduate, undergraduate and high school students with both training and active participation in research. All students will have opportunities to present their work at local and regional meetings as well as national (international) conferences. Through on-going programs at each institution, students from STEM under-represented groups will be recruited for research opportunities (and for entry into graduate programs). Additionally, through participation in the Georgia Coastal Research Council results of this work, and related issues in marine science and climate change, will be broadly disseminated to policy-makers and local (coastal) stakeholders through meetings, links to the GRGC website and listserv and targeted publications.