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首页> 外文学位 >The Impact of Mercury on Antioxidant Defenses in Shewanella oneidensis MR-1 and Characterization of Chromosomal mer operons in Xanthobacter autotrophicus Py2.
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The Impact of Mercury on Antioxidant Defenses in Shewanella oneidensis MR-1 and Characterization of Chromosomal mer operons in Xanthobacter autotrophicus Py2.

机译：汞对沙瓦氏假单胞菌MR-1抗氧化防御能力的影响以及自养黄单胞菌Py2的染色体mer操纵子的表征。

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摘要

Toxicological effects of mercury (Hg) on mammalian cells has been studied intensively, however little is known about the mechanisms of toxicity to bacterial cells lacking an Hg resistance (mer) operon. I researched physiological effect of Hg to Shewanella oneidensis MR-1. MR-1 is eight-fold more sensitive to ionic mercury [Hg(II)] under aerobic conditions than in fumarate reducing conditions, with both chronic and acute Hg exposure. Since more Hg is associated with cellular material in fumarate reducing conditions than in aerobic conditions, this increased sensitivity in aerobic conditions is not due to increased import of Hg into the cell. In fumarate reducing conditions, glutathione may provide protection against Hg, as glutathione levels decrease in a dose-dependent manner, but this does not occur in aerobic conditions. Hg(II) does not change the redox state of thioredoxin in MR-1 in either fumarate reducing conditions or aerobic conditions. However, treatment with 0.5 muM Hg(II) increases lipid peroxidation in aerobic conditions but not in fumarate reducing conditions in MR-1. It is concluded that the enhanced sensitivity of MR-1 to Hg(II) in aerobic conditions is not due to differences in intracellular responses, but due to damage at the cell envelope.;Xanthobacter autotrophicus Py2, an aerobic Alphaproteobacteria, was chosen as a model system to study interaction between Hg and soil bacteria. This study demonstrates that the proposed mer operons in Py2, mer1 and mer2, are mer operons based on the observation that 1) their gene transcription is activated by Hg(II); 2) they confer Hg(II) and MeHg resistance when expressed in Escherichia coli; 3) they confer Hg(II) reduction and MeHg demethylation when expressed in Escherichia coli. There is a new mer gene, referred to as merS, in both mer operons. The merSs' transcripts reside on the same polycistronic RNA with merAs and their protein products have glutathione reductase activity.
机译：汞（Hg）对哺乳动物细胞的毒理学作用已得到深入研究，但是对缺乏Hg抗性（mer）操纵子的细菌细胞的毒性机理知之甚少。我研究了汞对沙瓦氏假单胞菌MR-1的生理作用。 MR-1在有氧条件下对离子汞[Hg（II）]的敏感性比在富马酸盐还原条件下（无论是慢性还是急性汞暴露）敏感八倍。由于在富马酸减少条件下与细胞物质相关的汞比有氧条件下更多的汞与细胞物质有关，因此在有氧条件下这种增加的敏感性不是由于汞向细胞中的进口增加。在降低富马酸酯的条件下，由于谷胱甘肽水平以剂量依赖性方式降低，因此谷胱甘肽可以提供针对汞的保护，但这在有氧条件下不会发生。在富马酸还原条件或有氧条件下，Hg（II）不会改变MR-1中硫氧还蛋白的氧化还原状态。但是，在有氧条件下，用0.5μMHg（II）处理会增加脂质过氧化，而在MR-1中，在降低富马酸酯的条件下则不会。结论是在有氧条件下MR-1对Hg（II）的敏感性增强不是由于细胞内反应的差异，而是由于细胞包膜的损伤。;选择有氧Alproteobacteria的自养黄萎病菌Py2作为细菌。研究汞与土壤细菌之间相互作用的模型系统。这项研究表明，Py2，mer1和mer2中拟议的mer操纵子是mer操纵子，其基础是观察到：1）它们的基因转录被Hg（II）激活； 2）当在大肠杆菌中表达时，它们具有Hg（II）和MeHg抗性； 3）当在大肠杆菌中表达时，它们可降低Hg（II）和MeHg脱甲基。两个mer操纵子中都有一个新的mer基因，称为merS。 merSs的转录物与merA驻留在相同的多顺反子RNA上，其蛋白质产物具有谷胱甘肽还原酶活性。

著录项

  • 作者

    Wang, Yingjiao.;

  • 作者单位

    Clark University.;

  • 授予单位 Clark University.;
  • 学科 Molecular biology.;Environmental health.;Toxicology.;Cellular biology.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 81 p.
  • 总页数 81
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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