The role of heterotrophic bacteria in protecting cyanobacteria from hydrogen peroxide in coastal systems.

有毒的蓝藻有害藻华（CHABs）现在是一个全球性的问题，对人类和水生生物构成威胁，包括危及生命的疾病、海滩关闭、健康警报和饮用水处理厂关闭。该项目侧重于了解CHABs中存在的微生物与它们所居住的湖泊的化学成分之间相互作用所需的基础科学。特别是，它将研究过氧化氢的来源、命运和影响，过氧化氢是控制这些水华中存在的毒性和物种的潜在重要因素。这项研究将在伊利湖进行，伊利湖是1100万人的饮用水源，每年都受到chab的威胁。研究结果将直接整合到水管理者和其他利益相关者广泛使用的两个水质模型中。该项目将支持培养两名博士研究生，其中包括一名第一代大学学生，以及来自地球科学背景较少的本科生。研究也将纳入旨在增加地球科学多样性的外联活动，办法是让妇女和代表性不足的少数民族参加K-12以及大学和成人教育机构。该项目的总体目标是确定过氧化氢（H2O2）对近岸生态系统中蓝藻群落组成和功能的影响。伊利湖的初步结果表明，主要的初级生产者依靠异养细菌从短暂的高环境水平中吸收H2O2，这可能对蓝藻群落的成员有抑制作用。这表明H2O2在水生微生物生态学中起着重要的作用，但人们对其的了解还很少。现场采样、实验和最先进的“组学”相结合，将用于验证异养“帮手”分解H2O2是微生物相互作用和群落结构和功能的重要决定因素的总体假设。将对伊利湖进行研究是因为(i)它是接受高陆地养分径流的浅海地区的模型系统，（ii）它为比较研究提供了强大的近海和光和养分梯度，以及（iii）现有的采样基础设施、存档样本和初步数据可以利用。现场和实验室的实验和测量将被整合，以回答以下问题：Q1：是什么驱动H2O2浓度的时间动态？Q2：哪些酶和生物体通过生物H2O2衰变来保护群落？问题3：帮助者对H2O2的保护如何影响社区的组成和功能？这项研究将在培养液和自然水体中进行受控的实验室实验。测量H2O2浓度、生成和衰变速率，以及配套的化学和生物测量，将用于评估H2O2的主要来源和汇。分子工具将用于确定H2O2衰变的途径以及H2O2对蓝藻群落组成功能的影响。同时，实验将评估不同H2O2浓度对主要蓝藻生长速率的影响。这些实验结果将通过与该沿海生态系统中不同空间、时间和化学梯度的现场样品的微生物群落的结构和功能进行比较。将H2O2研究与自然系统中的“组学”相结合的方法是新颖的，将促进我们对微生物群落组成与功能之间关系的基础认识和理解。

Toxic cyanobacterial harmful algal blooms (CHABs) are now a worldwide problem that poses dangers for humans and aquatic organisms including life-threatening sickness, beach closures, health alerts, and drinking water treatment plant closures. This project focuses on the basic science needed to understand interactions between the microorganisms present in CHABs and the chemistry of the lakes they inhabit. In particular, it will study the sources, fate, and effects of hydrogen peroxide, which is a potentially important control on the toxicity and species present within these blooms. This research will be conducted in Lake Erie, a source of drinking water for 11 million people that is threatened by CHABs annually. Results will be directly integrated into two water quality models that are widely used by water managers and other stakeholders. This project will support the training of two PhD students, including a first-generation college attendee, and undergraduate students from backgrounds that are underrepresented in the earth sciences. Research will also be integrated into outreach aimed at increasing diversity in the earth sciences by involving women and underrepresented minorities in K-12 as well as college and adult educational settings.The overall goal of this project is to determine the influence of hydrogen peroxide (H2O2) on cyanobacterial community composition and function in nearshore ecosystems. Preliminary results from Lake Erie show that dominant primary producers rely on heterotrophic bacteria to draw down H2O2 from transiently high environmental levels that are likely inhibitory to members of the cyanobacterial community. This suggests that H2O2 plays important and still poorly understood roles in aquatic microbial ecology. A combination of field sampling, experiments, and state-of-the art "-omics" will be used to test the overall hypothesis that H2O2 decomposition by heterotrophic "helpers" is an important determinant of microbial interactions and community structure and function. Lake Erie will be studied because (i) it is a model system for shallow coastal areas receiving high terrestrial nutrient runoff, (ii) it offers strong inshore-offshore gradients of light and nutrients for comparative studies, and (iii) existing sampling infrastructure, archived samples, and preliminary data can be leveraged. Field and laboratory experiments and measurements will be integrated to answer the following questions: Q1: What drives the temporal dynamics of H2O2 concentrations? Q2: Which enzymes and organisms are responsible for protecting the community via biological H2O2 decay? Q3: How does protection from H2O2 by helpers influence the composition and function of the community? The study will perform controlled lab experiments on cultures and on natural waters during different points of the bloom. Measures of H2O2 concentrations and rates of production and decay, along with supporting chemical and biological measurements, will be used to assess the major sources and sinks of H2O2. Molecular tools will be used to determine the pathways underpinning H2O2 decay and the effect of H2O2 on cyanobacterial community composition function. In parallel, impacts of varying H2O2 concentrations on growth rates of major cyanobacteria will be assessed experimentally. These experimental results will be placed into context through comparisons with the structure and function of microbial communities from field samples across spatial, temporal, and chemical gradients in this coastal ecosystem. The approach of integrating studies of H2O2 with "-omics" in natural systems is novel, and will advance our fundamental knowledge and understanding of the relationship between microbial community composition and function.