Collaborative Research: Revealing the interplay between light, sulfur cycling, and oxygen production in cyanobacterial mats

在地球历史的大部分时间里，大气和海洋中的氧气（O2）水平太低，无法支持植物和动物的生命。蓝细菌是负责通过光合作用产生O2来氧化大气的微生物，从而使生命成为今天存在的生命。然而，推动大气中氧气含量上升的具体因素尚不清楚。特别是，鲜为人知的是控制蓝藻O2生产低O2，富硫化物的条件下，广泛存在于地球？进行性氧合。该项目将研究在模拟早期地球的条件下茁壮成长的现代蓝藻垫中的光，硫化氢，O2生产和微生物学之间的相互作用。研究和结果将被纳入努力招募，支持和保留在地球科学中代表性不足的学生，旨在实现劳动力多样化。为了传播所吸取的经验教训，将通过雷霆湾国家海洋保护区的游客中心与公众分享这一外联工作的成果，在会议上介绍这些成果，并在一份教育杂志上发表。最后，这个跨学科项目将在美国和德国之间建立密切的国际科学合作。该项目将调查地球生物学控制氧气（O2）生产的蓝藻垫在低氧和硫化物条件下。三个中心问题将被解决，以揭示耦合的微生物和地球化学过程。首先，光和硫化物及其相互作用是如何控制光合作用的平衡的？第二，如何观察到的变化，这些光合作用模式的代谢途径和活动的不同蓝藻种群的支持？第三，这些光合作用模式如何影响硫化物的产生速率，这可能是对有氧和缺氧光合作用平衡的反馈？解决这些问题背后的综合方法的总体目标是揭示特定的微生物种群，代谢途径和地球化学过程，支持地球化学。在围隔生态系统的控制实验将被用来跟踪作为光，硫化物和垫结构在昼夜周期的函数的含氧和缺氧光合作用的速率。与此同时，最先进的“组学”方法将在DNA、RNA和蛋白质水平上为这些微生物群落中代谢途径的动态提供前所未有的视角。相同的实验框架将用于测量在整个昼夜循环中在有氧和无氧光合作用下硫酸盐还原菌的代谢活性。这些非原位实验将植根于现实中，通过实地调查和直接测量垫在原位的地球化学参数的变化，代谢过程的评估和蛋白质组学分析的平行微剖面。更广泛地说，该项目将通过组建一个具有不同专业知识的跨学科团队来推进对微生物地球化学的理解，将地球化学过程与微生物种群和代谢途径联系起来，在DNA，RNA和蛋白质水平上具有前所未有的分辨率。

For most of Earth's history, oxygen (O2) levels in the atmosphere and oceans were too low to support plant and animal life. Cyanobacteria are microorganisms that were responsible for oxygenating the atmosphere by producing O2 via photosynthesis, thus enabling life as it is exists today. However, the specific factors that drove the rise of oxygen in the atmosphere are unknown. In particular, little is known about the controls on cyanobacterial O2 production under the low-O2, sulfide-rich conditions that were widespread during Earth?s progressive oxygenation. This project will study the interplay between, light, hydrogen sulfide, O2 production, and microbiology in modern cyanobacterial mats that thrive under conditions that mimic those of the early Earth. The research and results will be integrated into efforts to recruit, support, and retain underrepresented students in the geosciences in an effort aimed at diversifying the workforce. In order to disseminate lessons learned, results of this outreach effort will be shared with the public through the visitor center at the Thunder Bay National Marine Sanctuary, presented at conferences and published in an education journal. Finally, this interdisciplinary project will establish a close international scientific collaboration between the U.S. and Germany. This project will investigate geobiological controls on oxygen (O2) production by cyanobacterial mats under low-O2 and sulfidic conditions. Three central questions will be addressed to reveal the coupled microbial and geochemical processes. First, how do light and sulfide and their interactions control the balance of oxygenic and anoxygenic photosynthesis? Second, how are the observed shifts in these photosynthetic modes underpinned by metabolic pathways and activity of different cyanobacterial populations? Third, how do these photosynthetic modes affect the rate of sulfide production, which could represent a feedback on the balance of oxygenic and anoxygenic photosynthesis? The overall goal of the integrated approach behind addressing these questions is to reveal specific microbial populations, metabolic pathways, and geochemical processes that underpin mat biogeochemistry. Controlled experiments in mesocosms will be used to track rates of oxygenic and anoxygenic photosynthesis as a function of light, sulfide, and mat structure over a diel cycle. In parallel, state-of-the-art "omics" approaches will provide an unprecedented view of the dynamics of metabolic pathways in these microbial communities at the level of DNA, RNA, and protein. The same experimental framework will be used to measure the metabolic activity of sulfate reducing bacteria under oxygenic and anoxygenic photosynthesis across the diel cycle. These ex situ experiments will be rooted in reality via field investigations and direct measurements of mats in situ for parallel microprofiling of changes in geochemical parameters, assessment of metabolic processes, and proteomic analyses. More broadly, this project will advance the understanding of microbial geochemistry by forming an interdisciplinary team with diverse expertise to link geochemical processes to microbial populations and metabolic pathways with unprecedented resolution at the level of DNA, RNA, and protein.