Directly quantifying the isotopic fractionation associated with the key enzymes in microbial sulfate reduction

硫酸盐还原的微生物生活方式是现代和整个地球有机物氧化的核心。的历史。 这种与碳循环的联系，进而与气候的联系，通常是通过硫同位素研究来推断的，而硫同位素研究本身是通过对执行这一过程的现存细菌的实验来了解的。 然而，在其核心，细菌是由一套酶或催化剂驱动的，这些酶或催化剂进行了许多关键的化学反应。 在这项提案中，研究人员希望将第一个直接的同位素限制放在这种代谢中的两个关键酶步骤上：异化亚硫酸盐还原酶[DsrAB/C]和APS氧化还原酶[APSr]。 这些数据将允许更机械地理解细胞分离过程，这将提高我们阅读环境记录的能力。该研究项目将与葡萄牙ITQB的Instituto De Technologia Quimica E Biologica的Ines佩雷拉博士合作进行，他将为该项目提供必要的生物化学专业知识。一名哈佛研究生将往返于佩雷拉和约翰斯顿的实验室之间，获得同位素地球化学和生物化学方面宝贵的跨学科培训。这项研究的国际部分的旅行费用由NSF国际科学和工程办公室提供。

The microbial lifestyle of sulfate reduction is central to the oxidation of organic matter both in the Modern and throughout Earth?s history. This linkage to the carbon cycle, and in turn climate, is commonly inferred through sulfur isotope studies, which are themselves informed by experiments with extant bacteria that perform this process. At its core, however, bacteria are driven by a suite of enzymes, or catalysts, that conduct much of the critical chemistry. In this proposal, investigators look to place the first direct isotopic constraints on the two key enzymatic steps within this metabolism: dissimilatory sulfite reductase [DsrAB/C] and APS oxido-reductase [APSr]. This data will allow for a more mechanistic understanding of cellular fractionation processes, which will then sharpen our capacity to read environmental records.This research project will be conducted in collaboration with Dr. Ines Pereira of the Instituto De Technologia Quimica E Biologica, ITQB, Portugal, who will provide the biochemistry expertise necessary for the project. A Harvard graduate student will travel between the Pereira and Johnston's labs, acquiring valuable interdisciplinary training in isotope geochemistry and biochemistry. Travel costs for the international component of this research have been provided by the NSF Office of International Science and Engineering.