Collaborative Research: Experimental calibration of the isotopic content of marine sulfate

合作研究：海洋硫酸盐同位素含量的实验校准

• 批准号: 1536574
• 负责人: David Johnston
• 金额: $ 7.4万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1536574&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; calibration; isotopic

Collaborative Research: Experimental Calibration of the Isotopic Content of Marine SulfateAlexander BradleyID: 1536559Sulfur is an essential element to life, and its biogeochemical cycle is of interest to a broad range of scientific disciplines. A requirement for understanding the sulfur cycle involves revealing and quantifying the mechanisms by which microbes oxidize and reduce sulfur species. This can be done by tracing stable sulfur and oxygen isotopes. Enzymes play a key role in the cycling of sulfur, but the degree to which individual enzymes preferentially use specific oxygen isotopes (fractionation) is not known and prevents complete understanding of observed oxygen isotopes patterns in marine sulfate. This project will investigate isotope fractionation (oxygen and sulfur) associated with two key enzymes, which are involved in the metabolism of both sulfate reducing microbes and some sulfur oxidizing microbes. Resolving the influence of these enzymes on the isotopic composition of marine sulfate is important to stable isotope biogeochemistry and chemical oceanography. The project will serve as a vehicle to educate and train a postdoctoral researcher and undergraduate students, and will provide a teacher training opportunity in the investigators' labs to aid teachers in the design of student field trips and hands-on exercises for their students.The cycling of sulfur between its oxidized and reduced forms is a major determinant of the oxidation of organic matter in the oceans and underlying sediments, and microbes play a key role in the biogeochemical cycling of sulfur. One of the key tracers of microbial sulfur cycling involves measuring the distribution of stable isotopes among sulfur phases. A number of studies have shown that the stable oxygen isotope composition of sulfate is an informative way to investigate the sulfur cycle. Despite its utility, there are few direct constraints on how biology impacts the oxygen isotopes of sulfate. The goal of this project is to place quantitative constraints on the enzymatic oxygen isotope fractionation associated with microbial sulfate reduction. This project will involve in vitro investigations of the kinetic isotope fractionations associated with ATP sulfurylase and APS reductase, and incorporate the resulting data into an existing model for understanding isotope fractionation during sulfate reduction and its resulting influence on the isotopic composition of marine sulfate. These models will provide critical insight into the behavior of the sulfur cycle and evolution of marine chemistry over key timescales.

合作研究：海洋硫磺同位素含量的实验校准亚历山大·布拉德利ID：1536559硫磺是生命所必需的元素，其生物地球化学循环引起广泛科学学科的兴趣。了解硫循环的要求包括揭示和量化微生物氧化和还原硫物种的机制。这可以通过追踪稳定的硫和氧同位素来实现。酶在硫磺的循环中起着关键作用，但个别酶优先使用特定氧同位素(分馏)的程度尚不清楚，这阻碍了对海洋硫酸盐中观察到的氧同位素模式的完全了解。本项目将研究与硫酸盐还原微生物和一些硫氧化微生物代谢有关的两种关键酶的同位素分馏(氧和硫)。解决这些酶对海洋硫酸盐同位素组成的影响对于稳定同位素生物地球化学和化学海洋学具有重要意义。该项目将作为教育和培训博士后研究人员和本科生的工具，并将在研究人员实验室提供教师培训机会，帮助教师为学生设计实地考察和动手练习。硫在其氧化和还原形式之间的循环是海洋和底层沉积物中有机物氧化的主要决定因素，微生物在硫的生物地球化学循环中发挥关键作用。微生物硫循环的关键示踪剂之一涉及测量稳定同位素在硫相之间的分布。大量研究表明，硫酸盐稳定的氧同位素组成是研究硫循环的一种有用的方法。尽管它有用，但对于生物如何影响硫酸盐的氧同位素，几乎没有直接的限制。该项目的目标是对与微生物硫酸盐还原相关的酶促氧同位素分馏施加定量限制。该项目将涉及与三磷酸腺苷硫化酶和APS还原酶有关的动力学同位素分馏的体外研究，并将结果数据纳入现有模型，以了解硫酸盐还原过程中的同位素分馏及其对海洋硫酸盐同位素组成的影响。这些模型将为硫循环的行为和海洋化学在关键时间尺度上的演变提供重要的洞察力。