Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake
Anaerobic methane oxidation coupled to denitrification is the dominant methane sink in a deep lake
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DOI：
10.1073/pnas.1411617111
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发表时间：
2014-12-23
影响因子：
11.1
通讯作者：
Schink, Bernhard
中科院分区：
文献类型：
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作者：
Deutzmann, Joerg S.;Stief, Peter;Schink, Bernhard
厌氧甲烷氧化与反硝化相结合，也称为“硝酸盐/亚硝酸盐依赖性厌氧甲烷氧化”(n-damo)，于 2006 年被发现。此后，只有少数研究在自然环境中鉴定了这一过程以及相关微生物。在水生沉积物中，氧气和硝酸盐消耗区非常接近，可以将 n-damo 掩盖为需氧甲烷氧化。因此，我们利用不依赖于培养的分子技术研究了博登湖沉积物中与 Candidatus Mmethylomirabilis oxyfera 相关的反硝化甲烷氧化菌的垂直分布和丰度。此外，甲烷氧化和硝酸盐消耗区域的垂直分布是根据未受干扰的沉积物岩心中的高分辨率微传感器剖面推断的。 M. oxyfera 类细菌在浅水地点（滨海沉积物）实际上不存在，而在深水地点（深海沉积物）非常丰富。在深部沉积物中，M. oxyfera 类细菌的垂直分布在缺氧层中显示出明显的峰值，该峰值与甲烷氧化和硝酸盐消耗区域一致，这强烈表明 M. oxyfera 类细菌进行了 n-damo。根据细胞密度计算出的潜在 n-damo 速率 (660-4,890 mu mol CH4.m(-2).d(-1)) 和根据微传感器剖面计算出的实际速率 (31-437 mu mol CH4.m(-2).d(-1)) 都足够高，足以防止仅通过此过程从深部沉积物中释放甲烷。此外，当硝酸盐被添加到暴露于缺氧条件的沉积物核心中时，n-damo区域在沉积物表面下方重新建立，完全阻止了沉积物中的甲烷释放。我们得出的结论是，如果缺氧区有硝酸盐，以前被忽视的 n-damo 过程可能是稳定淡水环境中的主要甲烷汇。
Anaerobic methane oxidation coupled to denitrification, also known as "nitrate/nitrite-dependent anaerobic methane oxidation" (n-damo), was discovered in 2006. Since then, only a few studies have identified this process and the associated microorganisms in natural environments. In aquatic sediments, the close proximity of oxygen-and nitrate-consumption zones can mask n-damo as aerobic methane oxidation. We therefore investigated the vertical distribution and the abundance of denitrifying methanotrophs related to Candidatus Methylomirabilis oxyfera with cultivation-independent molecular techniques in the sediments of Lake Constance. Additionally, the vertical distribution of methane oxidation and nitrate consumption zones was inferred from high-resolution microsensor profiles in undisturbed sediment cores. M. oxyfera-like bacteria were virtually absent at shallow-water sites (littoral sediment) and were very abundant at deep-water sites (profundal sediment). In profundal sediment, the vertical distribution of M. oxyfera-like bacteria showed a distinct peak in anoxic layers that coincided with the zone of methane oxidation and nitrate consumption, a strong indication for n-damo carried out by M. oxyfera-like bacteria. Both potential n-damo rates calculated from cell densities (660-4,890 mu mol CH4.m(-2).d(-1)) and actual rates calculated from microsensor profiles (31-437 mu mol CH4.m(-2).d(-1))were sufficiently high to prevent methane release from profundal sediment solely by this process. Additionally, when nitrate was added to sediment cores exposed to anoxic conditions, the n-damo zone reestablished well below the sediment surface, completely preventing methane release from the sediment. We conclude that the previously overlooked n-damo process can be the major methane sink in stable freshwater environments if nitrate is available in anoxic zones.