LEXEN: Biological Innovations During Two Periods Of Extreme Environmental Stress

DEB-0085567Janet L.西弗特博士珍妮特湖莱斯大学的西弗特和詹姆斯·F·宾夕法尼亚州立大学的Kasting获得了极端环境中的生命（LExEn）计划的资助，通过使用气候/地球化学模拟和分子系统技术的组合来追踪地球历史上的过去环境危机。模型将有助于预测什么样的生物能够改变大气，并模拟不同种类的微生物之间的相互作用。例如，最初产生甲烷的古生菌可能占主导地位，然后被产生氧气的细菌（蓝细菌）所取代。已知蓝细菌至少存在了2.7 Ga，那么为什么氧气的增加不会再发生0.3 Ga？他们的模型将试图解释这样的差异。分子系统学技术将使用DNA序列数据来追踪生物体及其基因组的祖先。这些重建的祖先将揭示哪些生物最有可能存在，是否有可能进化出新的新陈代谢类型的“分子化石”的证据，以及气候/地球化学模型的假设是否有意义。

DEB-0085567Janet L. SiefertDr. Janet L. Siefert of Rice University, and Dr. James F. Kasting of Pennsylvania State University have been awarded a grant from the Life in Extreme Environments (LExEn) program to trace past environmental crises in Earth history by using a combination of climate/biogeochemistry modeling and molecular systematic techniques. Models will help predict what kinds of organisms were capable of making the changes in atmosphere and to simulate interaction of different species ofmicroorganisms. For instance, initially archaea that produced methane might have dominated and then were usurped by bacteria that produced oxygen (cyanobacteria). Cyanobacteria are known to have existed by at least 2.7 Ga, so why does the rise in oxygen not occur for another 0.3 Ga? Their models will attempt to explain discrepancies such as this. Molecular systematic techniques will use DNA sequence data to track the ancestry of organisms and their genomes. These reconstructed ancestries will reveal which organisms were most likely present, whether there is evidence of 'molecular fossils' of new kinds of metabolism that may have evolved, and whether or not the assumptions of the climate/biogeochemical models make sense.