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）含量太低，无法维持动植物的生命。蓝藻是一种微生物，通过光合作用产生氧气，使大气氧化，从而使今天存在的生命成为可能。然而，导致大气中氧气含量上升的具体因素尚不清楚。特别是，在低氧、富含硫化物的条件下，对蓝藻产氧的控制知之甚少。S渐进氧合。该项目将研究在模拟早期地球条件下茁壮成长的现代蓝藻垫中，光、硫化氢、氧气生产和微生物学之间的相互作用。这些研究和成果将被纳入招募、支持和留住地球科学领域代表性不足的学生的努力中，以实现劳动力多样化。为了传播经验教训，将通过桑德湾国家海洋保护区的游客中心与公众分享这一推广工作的成果，并在会议上展示，并在教育期刊上发表。最后，这个跨学科的项目将在美国和德国之间建立密切的国际科学合作。该项目将研究在低氧和硫化物条件下蓝藻席对氧气（O2）生产的地球生物学控制。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如何控制含氧和无氧光合作用的平衡？其次，观察到的这些光合模式的变化是如何由不同蓝藻种群的代谢途径和活动所支撑的？第三，这些光合作用模式如何影响硫化物的产生速度，硫化物的产生可能代表着对含氧和无氧光合作用平衡的反馈。解决这些问题的综合方法的总体目标是揭示支撑生物地球化学的特定微生物种群、代谢途径和地球化学过程。中生态系统的对照实验将用于跟踪在一个周期中，含氧和无氧光合作用的速率作为光、硫化物和基质结构的函数。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的代谢途径动力学提供前所未有的视角。同样的实验框架将被用于测量硫酸盐还原菌在整个循环中有氧和无氧光合作用下的代谢活性。这些非原位实验将根植于现实，通过实地调查和原位垫的直接测量，以平行微剖面分析地球化学参数的变化，评估代谢过程和蛋白质组学分析。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，以前所未有的DNA、RNA和蛋白质水平的分辨率将地球化学过程与微生物种群和代谢途径联系起来，从而促进对微生物地球化学的理解。

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.