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Isotopic evidence for biological nitrogen fixation by molybdenum-nitrogenase from 3.2 Gyr

机译：3.2 Gyr的钼氮酶对生物固氮的同位素证据

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摘要

Nitrogen is an essential nutrient for all organisms that must have been available since the origin of life. Abiotic processes including hydrothermal reduction', photochemical reactions', or lightning disc(h)arge' could have converted atmospheric Ny into assimilable NH4, HCN, or NO species, collectively termed fixed nitrogen. But these sources may have been small on the early Earth, severely limiting the size of the primordial biosphere'. The evolution of the nitrogenfixing enzyme nitrogenase, which reduces atmospheric Ny to organic NH4, thus represented a major breakthrough in the radiation of life, but its timing is uncertain'''. Here we present nitrogen isotope ratios with a mean of 0.0 1.2%0 from marine and fluvial sedimentary rocks of prehnite-pumpellyite to greenschist metamorphic grade between 3.2 and 2.75 billion years ago. These data cannot readily be explained by abiotic processes and therefore suggest biological nitrogen fixation, most probably using molybdenum-based nitrogenase as opposed to other variants that impart significant negative fractionations'. Our data place a minimum age constraint of 3.2 billion years on the origin of biological nitrogen fixation and suggest that molybdenum was bioavailable in the mid-Archaean ocean long before the Great Oxidation Event.
机译：氮是自生命起源以来必须存在的所有生物的必需营养素。非生物过程包括水热还原'，光化学反应'或闪电盘（h）可能将大气中的Ny转化为可吸收的NH4，HCN或NO物种，统称为固定氮。但是在地球早期，这些来源可能很小，严重限制了原始生物圈的大小。固氮酶固氮酶的进化将大气中的Ny还原为有机NH4，因此代表了生命辐射的重大突破，但其时机尚不确定''。在这里，我们提出了从3.2亿2千5百亿年前的绿榴石-磷灰石的海相和河流相沉积岩到绿片岩变质品级的平均氮同位素比为0.0 1.2％0。这些数据无法通过非生物过程轻松解释，因此建议进行生物固氮，最有可能使用基于钼的固氮酶，而不是其他具有显着负分馏作用的变体。我们的数据对生物固氮的来源设置了32亿年的最小年龄限制，并表明在大氧化事件发生之前很久，钼就已在Archaean海洋中被生物利用。

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  • 来源
    《Nature》 |2015年第7549期|666-669|共4页
  • 作者

    Stueeken Eva E.; Buick Roger; Guy Bradley M.; Koehler Matthew C.;

  • 作者单位

    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA|Univ Washington, Astrobiol Program, Seattle, WA 98195 USA;

    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA|Univ Washington, Astrobiol Program, Seattle, WA 98195 USA;

    Univ Johannesburg, Dept Geol, ZA-2006 Auckland Pk, South Africa;

    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA|Univ Washington, Astrobiol Program, Seattle, WA 98195 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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  • 正文语种 eng
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