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首页> 外文学位 >Coupled nitrogen and oxygen isotope fractionation of nitrate imparted during its assimilation and dissimilatory reduction by unicellular plankton.
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Coupled nitrogen and oxygen isotope fractionation of nitrate imparted during its assimilation and dissimilatory reduction by unicellular plankton.

机译：硝酸盐在氮的吸收过程中的氮和氧同位素耦合分馏和单细胞浮游生物的异化还原。

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摘要

I report the first measurements of coupled nitrogen (N) and oxygen (O) isotopic variations of nitrate (NO3- ) during its assimilation and dissimilatory reduction by laboratory cultures of marine and freshwater plankton. I derive the N and O kinetic isotope effects for nitrate assimilation by strains of marine and freshwater phytoplankton, as well as N and O isotope effects for denitrification by marine and freshwater strains of denitrifying bacteria. Large inter- and intra-species variations in the N and O isotope effects were observed among phytoplankton and among denitrifiers. However, the O isotope effect associated with either nitrate consumption or denitrification always co-varied with the N isotope effect, such that the 18O/16O and 15N/14N of nitrate changed concomitantly with a consistent ratio of ∼1:1, regardless of species or culture conditions. A single strain of denitrifiers, Rhodobacter sphaeroides, showed an O-to-N co-variation of 0.6.; My results indicate that the dominant driver of the N and O isotope effects is nitrate reductase. The O-to-N ratio of I owes to the isotopic signature of the various nitrate reductases involved in nitrate reduction, namely the eukaryotic assimilatory nitrate reductase (eukNR), the prokaryotic assimilatory nitrate reductase (NAS), as well as the prokaryotic respiratory nitrate reductase (NAR). The variability in the observed magnitude of the N and O isotope effects is attributed to changes in the ratio of cellular nitrate uptake and efflux. The unusual O-to-N ratio of 0.6 observed for R. sphaeroides is imprinted on nitrate by the periplasmic auxiliary nitrate reductase NAP.; I also report a novel method to remove nitrite from samples for isotopic analysis of nitrate with the 'denitrifier method,' which measures the isotopic composition of nitrate and nitrite concomitantly. Nitrite is removed with ascorbate while purging with an inert gas. The method is non-toxic (hence compatible with the denitrifier method) and does not alter the concentration or the isotopic composition of nitrate in the samples.; The findings reported here provide insight into the physiological mechanisms underlying nitrate isotopic fractionation during its assimilation and dissimilatory reduction. The trends observed in culture underline the biological systematics from which to interpret in situ measurements of coupled N and O isotopes of nitrate. Moreover, this work emphasizes the need to investigate the environmental factors that potentially contribute to variations in the magnitude of the N and O isotope effects in situ.
机译：我报告了硝酸盐（NO3-）在被海洋和淡水浮游生物的同化和异化还原过程中耦合的氮（N）和氧（O）同位素变化的首次测量。我推导了海洋和淡水浮游植物菌株对硝酸盐同化的N和O动力学同位素效应，以及海洋和淡水反硝化细菌菌株对N和O同位素的反硝化作用。在浮游植物之间和反硝化动物之间观察到物种间和物种间氮和氧同位素效应的大差异。但是，与硝酸盐消耗或反硝化有关的O同位素效应总是与N同位素效应共变，因此，无论何种物种，硝酸盐的18O / 16O和15N / 14N都以〜1：1的恒定比率伴随变化。或文化条件。单个反硝化菌球形球形红细菌显示O到N的协方差为0.6。我的结果表明，N和O同位素效应的主要驱动因素是硝酸还原酶。 I的O对N比归因于参与硝酸盐还原的各种硝酸盐还原酶的同位素特征，即真核同化硝酸盐还原酶（eukNR），原核同化硝酸盐还原酶（NAS）以及原核呼吸硝酸盐还原酶（NAR）。 N和O同位素效应的观测值的可变性归因于细胞硝酸盐吸收和流出比率的变化。通过球形的辅助硝酸还原酶NAP，在球形硝酸盐上发现了不寻常的O.N比率，为0.6。我还报告了一种新的方法，即“脱硝器法”从样品中去除亚硝酸盐进行硝酸盐同位素分析，该方法同时测量硝酸盐和亚硝酸盐的同位素组成。在用惰性气体吹扫的同时，用抗坏血酸除去亚硝酸盐。该方法是无毒的（因此与反硝化方法兼容），并且不会改变样品中硝酸盐的浓度或同位素组成。这里报道的发现提供了对硝酸盐同位素同化和异化还原过程中潜在的生理机制的深入了解。在文化中观察到的趋势强调了从生物学系统解释硝酸盐N和O耦合同位素的原位测量的基础。此外，这项工作强调需要研究可能导致原位N和O同位素效应幅度变化的环境因素。

著录项

  • 作者

    Granger, Julie.;

  • 作者单位

    The University of British Columbia (Canada).;

  • 授予单位 The University of British Columbia (Canada).;
  • 学科 Biogeochemistry.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 186 p.
  • 总页数 186
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生物地球化学、气体地球化学;
  • 关键词

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