Dekas Anne E, Poretsky Rachel S, Orphan Victoria J
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2009 Oct 16;326(5951):422-6. doi: 10.1126/science.1178223.
Nitrogen-fixing (diazotrophic) microorganisms regulate productivity in diverse ecosystems; however, the identities of diazotrophs are unknown in many oceanic environments. Using single-cell-resolution nanometer secondary ion mass spectrometry images of 15N incorporation, we showed that deep-sea anaerobic methane-oxidizing archaea fix N2, as well as structurally similar CN-, and share the products with sulfate-reducing bacterial symbionts. These archaeal/bacterial consortia are already recognized as the major sink of methane in benthic ecosystems, and we now identify them as a source of bioavailable nitrogen as well. The archaea maintain their methane oxidation rates while fixing N2 but reduce their growth, probably in compensation for the energetic burden of diazotrophy. This finding extends the demonstrated lower limits of respiratory energy capable of fueling N2 fixation and reveals a link between the global carbon, nitrogen, and sulfur cycles.
固氮（重氮营养型）微生物调节着不同生态系统的生产力；然而，在许多海洋环境中，重氮营养菌的身份尚不清楚。通过使用15N掺入的单细胞分辨率纳米二次离子质谱图像，我们发现深海厌氧甲烷氧化古菌能够固定N2以及结构相似的CN-，并与硫酸盐还原细菌共生体共享产物。这些古菌/细菌共生体已被公认为是底栖生态系统中甲烷的主要汇，而我们现在也将它们确定为生物可利用氮的一个来源。古菌在固定N2的同时维持其甲烷氧化速率，但降低了生长速度，这可能是为了补偿固氮的能量负担。这一发现扩展了已证明的能够为N2固定提供能量的呼吸能量下限，并揭示了全球碳、氮和硫循环之间的联系。
