Dissertation Enhancement: Investigating Chloroflexi mats at a Japanese Hot Spring as a Model for Anoxygenic Stromatolites

虽然我们通常认为地球上的生命是复杂的多细胞生物，比如植物和动物，但这些生物只是在最近才进化出来的，在地球过去的6亿年里？45亿年的历史。早些时候，地球上的所有生命都是微生物，由细菌和藻类等有机体组成。尽管这些生物看起来很简单，但它们对生物学中一些最重要的发明负有责任，包括氧气光合作用。吸收水、阳光和二氧化碳并产生糖和氧气的能力。虽然这个过程发生在今天的植物中，但它最初是由一群叫做蓝藻的生物发明的。通过光合作用产生氧气的蓝藻是如何彻底改变地球的？通过产生臭氧层，为有氧呼吸提供氧气，并使氧气在岩石的化学风化中发挥作用，地球表面起了作用。这种变化发生在大约23亿年前。它不是吗?然而，我们不太清楚蓝藻是在这个时期还是在更早的地球历史上进化和发明了含氧光合作用。因为单个细菌不会留下好的化石，所以寻找它们进化时间的最好方法之一就是观察保存在古代岩石中的微生物席。该奖项支持美国研究生路易斯·沃德的博士论文研究，研究在日本温泉中形成的微生物垫，在那里，类似的微生物垫是由蓝藻和氯藻形成的，这是一组进行光合作用但不释放氧气的细菌。通过研究这两种类型的地垫，观察它们之间的差异，就有可能确定微生物地垫的哪些特征被保存在岩石记录中，并可以用来区分哪一组生物产生了它们。通过将这些特征与岩石记录中保存的微生物席进行比较，我们可以更好地了解蓝藻、光合作用和氧气的历史，进而了解地球上生命的起源。这项研究将与日本东京都大学环境微生物群落专家肖恩·麦格林教授合作进行。叠层石是层状的、增生的沉积结构，通常是由相互作用形成的。微生物和沉积物。有犯罪记录的人50亿年前，它们就在地球上地球上最早的生命证据虽然相似的结构可能在缺乏生物学的情况下形成，但对现代类似物的广泛研究为鉴定生物原性提供了强有力的标准。许多古老的叠层石。已知的现代叠层石类似物是由富氧蓝藻形成的，这导致将古代叠层石解释为蓝藻存在进行富氧光合作用的指标。然而，独立的地质指标表明，蓝藻和氧气的出现相对较晚，更接近于氧气的出现。35 Ga。因为蓝藻是从无氧的祖先进化而来的，所以可以想象，早期的叠层石是由无氧的光养生物形成的，但我们对这是否会发生以及如何发生知之甚少。为了解决这一难题，我们建议开发和研究一个由绿柔菌组成的模型叠层石形成系统，绿柔菌是一门具有无氧光异养能力的兼性好氧丝状细菌。为了促进这项工作，该奖项支持与东京城市大学（Tokyo Metropolitan University）的研究人员合作，他们是该领域最重要的专家之一。本研究主要对氯氟草的分离、培养及生理研究进行了综述。该项目将通过在日本中霸温泉的温泉中使用天然氯氟烃垫来加强。这个独特的机会将允许有效地开发一个模型系统。无氧叠层石采用氯氟烃纯培养和天然温泉垫。该系统将直接测试叠层石是否可以在没有光合作用的情况下形成（通过将其培养为需氧异养生物），以及进行无氧光养的生物体是否可以形成叠层石。

Although we usually think of life on Earth in terms of complex multicellular organisms like plants and animals, these have evolved only relatively recently, in the last 600 million years of Earth?s 4.5 billion year history. Earlier, all life on Earth was microbial, made up of organisms like bacteria and algae. Although these organisms look simple they are responsible for some of the most important inventions in biology, including oxygenic photosynthesis?the ability to take water, sunlight, and CO2 and to produce sugar and oxygen. While this process occurs in plants today it was first invented by a group of organisms called Cyanobacteria. The production of oxygen by photosynthetic Cyanobacteria completely changed how the Earth?s surface worked, by producing the ozone layer, providing oxygen for aerobic respiration, and allowing oxygen to play a role in chemical weathering of rocks. This change occurred about 2.3 billion years ago. It isn?t well understood, however, whether Cyanobacteria evolved and invented oxygenic photosynthesis right around this time or much earlier in Earth history. Because individual bacteria don't leave good fossils, one of the best ways of looking for when they evolved is by observing preserved microbial mats in ancient rocks. This award supports doctoral dissertation research by U.S. graduate student Lewis Ward to study microbial mats forming in hot springs in Japan, where similar microbial mats are being formed today by Cyanobacteria and Chloroflexi, a group of bacteria which performs photosynthesis but without releasing oxygen. By studying these two types of mats and seeing how they differ, it is possible to determine which features of microbial mats are preserved in the rock record and can be used to distinguish which group of organisms produced them. By comparing these features to preserved microbial mats throughout the rock record, we can better understand the history of Cyanobacteria, photosynthesis, and oxygen and, by extension, the origins of life on Earth. This research will be conducted in collaboration with Professor Shawn McGlynn, an expert on microbial communities in the environment, at Tokyo Metropolitan University in Japan.Stromatolites are layered, accretionary sedimentary structures often formed by the interaction
of microbes with sediments. With a record dating back 3. 5 billion years, they are among the
 earliest evidence for life on Earth. While similar structures may form in the absence of biology, extensive investigation of modern analogs provides robust criteria for identifying the biogenicity
 of many ancient stromatolites. Known modern stromatolite analogs are formed by oxygenic Cyanobacteria, which leads to interpretation of ancient stromatolites as indicators of the presence of Cyanobacteria performing oxygenic photosynthesis. However, independent geological proxies suggest that Cyanobacteria and oxygen appear relatively late, closer to the rise of oxygen ca. 2. 35 Ga. Because Cyanobacteria evolved from anoxygenic ancestors, it is conceivable that early stromatolites were formed by anoxygenic phototrophs, but we have a poor understanding of whether and how this would 
occur. In order to resolve this conundrum we propose to develop and study a model stromatolite-forming system composed of Chloroflexi--a phylum of facultatively aerobic filamentous bacteria capable of anoxygenic photoheterotrophy. To catalyze this work, this award supports a collaboration with researchers at Tokyo Metropolitan University who are among the foremost experts in the
world at the isolation, cultivation, and physiological study of Chloroflexi. This project will be enhanced by access to natural Chloroflexi mats at a hot spring at the Nakabusa Onsen in Japan. This unique opportunity will allow effective development of a model system for
anoxygenic stromatolites using Chloroflexi in both pure culture and using natural hot spring mats. This system will directly test whether or not stromatolites can form in the absence of photosynthesis (by growing them as aerobic heterotrophs), and if organisms performing anoxygenic phototrophy can form stromatolites.