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首页> 外文期刊>Applied Microbiology >Diversity, Abundance, and Potential Activity of Nitrifying and Nitrate-Reducing Microbial Assemblages in a Subglacial Ecosystem
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Diversity, Abundance, and Potential Activity of Nitrifying and Nitrate-Reducing Microbial Assemblages in a Subglacial Ecosystem

机译：亚冰川生态系统中硝化和减少硝酸盐的微生物群落的多样性，丰度和潜在活性

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Subglacial sediments sampled from beneath Robertson Glacier (RG), Alberta, Canada, were shown to harbor diverse assemblages of potential nitrifiers, nitrate reducers, and diazotrophs, as assessed by amoA , narG , and nifH gene biomarker diversity. Although archaeal amoA genes were detected, they were less abundant and less diverse than bacterial amoA , suggesting that bacteria are the predominant nitrifiers in RG sediments. Maximum nitrification and nitrate reduction rates in microcosms incubated at 4°C were 280 and 18.5 nmol of N per g of dry weight sediment per day, respectively, indicating the potential for these processes to occur in situ . Geochemical analyses of subglacial sediment pore waters and bulk subglacial meltwaters revealed low concentrations of inorganic and organic nitrogen compounds. These data, when coupled with a C/N atomic ratio of dissolved organic matter in subglacial pore waters of ～210, indicate that the sediment communities are N limited. This may reflect the combined biological activities of organic N mineralization, nitrification, and nitrate reduction. Despite evidence of N limitation and the detection of nifH , we were unable to detect biological nitrogen fixation activity in subglacial sediments. Collectively, the results presented here suggest a role for nitrification and nitrate reduction in sustaining microbial life in subglacial environments. Considering that ice currently covers 11% of the terrestrial landmass and has covered significantly greater portions of Earth at times in the past, the demonstration of nitrification and nitrate reduction in subglacial environments furthers our understanding of the potential for these environments to contribute to global biogeochemical cycles on glacial-interglacial timescales.
机译：根据amoA，narG和nifH基因生物标记物的多样性评估，从加拿大艾伯塔省罗伯逊冰川（RG）下方采样的冰下沉积物具有潜在的硝化剂，硝酸盐还原剂和重氮营养菌的各种组合。尽管检测到古细菌amoA基因，但它们比细菌amoA丰富且多样性低，这表明细菌是RG沉积物中的主要硝化剂。在4°C下孵育的微观世界中，最大硝化作用和硝酸盐还原速率分别为每克干重沉积物每天280和18.5 nmol N，这表明这些过程可能就地发生。对冰川下沉积物孔隙水和大量冰川下熔体水的地球化学分析表明，无机和有机氮化合物的浓度较低。这些数据，再加上〜210冰川下孔隙水中溶解的有机物的C / N原子比，表明沉积物群落受到N的限制。这可能反映了有机氮矿化，硝化和硝酸盐还原的综合生物活性。尽管有氮限制和检测到nifH的证据，我们仍无法检测到冰川下沉积物中的生物固氮活性。总的来说，这里提出的结果表明硝化作用和硝酸盐还原作用在冰川下环境中维持微生物生命中发挥了作用。考虑到冰层目前覆盖了陆地陆地的11％，过去有时覆盖了地球的大部分区域，因此在冰下环境中硝化作用和硝酸盐还原作用的证明进一步加深了我们对这些环境潜在影响全球生物地球化学循环的认识在冰川间时间尺度上。

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