LEXEN: Biological Innovations During Two Periods Of Extreme Environmental Stress

janet L. siefert博士；莱斯大学的Janet L. Siefert和宾夕法尼亚州立大学的James F. Kasting博士获得了“极端环境中的生命”（LExEn）项目的资助，通过结合气候/生物地球化学模型和分子系统技术来追踪地球历史上过去的环境危机。模型将有助于预测什么样的生物能够使大气发生变化，并模拟不同种类的微生物之间的相互作用。例如，最初产生甲烷的古细菌可能占主导地位，然后被产生氧气的细菌（蓝藻）所取代。众所周知，蓝藻至少在2.7 Ga之前就存在了，那么为什么在0.3 Ga之后氧含量没有上升呢？他们的模型将试图解释诸如此类的差异。分子系统技术将使用DNA序列数据来追踪生物体的祖先及其基因组。这些重建的祖先将揭示哪些生物最有可能存在，是否有证据表明可能已经进化出新的代谢类型的“分子化石”，以及气候/生物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.