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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >In situ microbial metabolism as a cause of gas anomalies in ice
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In situ microbial metabolism as a cause of gas anomalies in ice

机译：原位微生物代谢是冰中气体异常的原因

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Isolated spikes of anomalously high concentrations of N_2O have been reported at depths in Greenland and Antarctic ice cores corresponding to narrow time intervals over the past ≈10~5 years. Now, using a calibrated spectrofluorimeter to map protein-bound Trp, a proxy for microbes, versus depth in the 3,053-m GISP2 ice core, we find six depths at which localized spikes of high cell concentrations coincide with N_2O spikes. We show that the excess gases are consistent with accumulation of in situ metabolic wastes during residence times of the excess microbes in the ice. Because of sparseness of N_2O measurements and our spectrofluorimetry versus depth, the total number of microbially produced N_2O spikes in GISP2 is probably much larger than six. Spikes of excess methanogens coincident with CH_4 spikes are found at three depths in the bottom 3% of GISP2, most likely because of methanogenic metabolism in the underlying silty ice, followed by turbulent flow of the lowest ≈90 m of ice. The apparent rates of in situ production of N_2O and CH_4 spikes by metabolism are observed to be consistent with a single activation energy, U, and maintain proportionality to exp(-U/RT) over the entire temperature range down to -40℃. Fluorescence of nonmicrobial aerosols in GISP2 ice is distinguishable from microbial fluorescence by its different emission spectra. Our spectrofluorimetric scans throughout the GISP2 ice core lead us to conclude that both microbes and nonmicrobial aerosols are deposited in discontinuous bursts, which may provide a tool for studying wind storms in the distant past.
机译：据报道，在过去的约10〜5年中，格陵兰和南极冰芯的深处出现了孤立的异常高浓度N_2O峰值，这对应于狭窄的时间间隔。现在，使用校准的荧光分光光度计绘制结合蛋白质的Trp（微生物的代理）与3,053-m GISP2冰芯中的深度的关系图，我们发现了六个深度，高细胞浓度的局部峰值与N_2O峰值重合。我们表明，过量的气体与过量的微生物在冰中停留时间期间原位代谢废物的积累是一致的。由于N_2O测量的稀疏性以及我们的荧光分光光度法与深度的关系，GISP2中微生物产生的N_2O尖峰总数可能比六个大得多。在GISP2底部3％的三个深度处发现了与CH_4尖峰同时发生的过量产甲烷菌尖峰，这很可能是由于下层粉质冰中的产甲烷代谢作用，随后是最低≈90m的冰的湍流。观察到通过代谢原位产生N_2O和CH_4峰值的速率与单个活化能U一致，并且在整个-40℃的温度范围内都与exp（-U / RT）保持比例。 GISP2冰中非微生物气溶胶的荧光可以通过其不同的发射光谱与微生物荧光区分开。我们对整个GISP2冰芯进行的荧光光谱扫描使我们得出结论，微生物和非微生物气溶胶均以不连续的爆发形式沉积，这可能是研究遥远过去的暴风雨的工具。

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