Max Planck Institute for Marine Microbiology, Celsiusstraße 1, 28359 Bremen, Germany. Alfred Wegener Institute for Polar and Marine Research, 27515 Bremerhaven, Germany.
Environ Microbiol Rep. 2009 Oct;1(5):370-6. doi: 10.1111/j.1758-2229.2009.00074.x. Epub 2009 Sep 23.
The anaerobic oxidation of methane (AOM) by methanotrophic archaea and sulfate-reducing bacteria is the major sink of methane formed in marine sediments. The study of AOM as well as of methanogenesis in different habitats is essentially connected with the in situ analysis of stable isotope ((13) C/(12) C, D/H) signatures (δ-values). For their kinetic interpretation, experimental (cultivation-based) isotope fractionation factors (α-values) are richly available in the case of methanogenesis, but are scarce in the case of AOM. Here we used batch enrichment cultures with high AOM activity and without background methanogenesis from detrital remnants to determine (13) C/(12) C and D/H fractionation factors. The enrichment cultures which originated from three marine habitats (Hydrate Ridge, NE Pacific; Amon Mud Volcano, Mediterranean Sea; NW shelf, Black Sea) were dominated by archaeal phylotypes of anaerobic methanotrophs (ANME-2 clade). Isotope fractionation factors calculated from the isotope signatures as a function of the residual proportion of methane were 1.012-1.039 for (13) CH4 /(12) CH4 and 1.109-1.315 for CDH3 /CH4 . The present values from in vitro experiments were significantly higher than values previously estimated from isotope signature distributions in marine sediment porewater, in agreement with the overlap of other processes with AOM in the natural habitat.
甲烷厌氧氧化（AOM）由甲烷营养古菌和硫酸盐还原菌共同作用完成，是海洋沉积物中甲烷形成的主要消耗途径。对 AOM 和不同生境中甲烷生成的研究与稳定同位素（（13）C/（12）C、D/H）特征（δ 值）的原位分析密切相关。对于动力学解释，在甲烷生成的情况下，实验（基于培养）同位素分馏因子（α 值）非常丰富，但在 AOM 的情况下却很少。在这里，我们使用高 AOM 活性且无碎屑残留背景甲烷生成的批量富集培养物来确定（13）C/（12）C 和 D/H 分馏因子。这些来自三个海洋生境（太平洋东北部的 Hydrate Ridge；地中海的 Amon Mud Volcano；黑海西北大陆架）的富集培养物主要由厌氧甲烷氧化古菌（ANME-2 分支）的古菌型组成。从同位素特征随甲烷残留比例的函数计算出的同位素分馏因子为 1.012-1.039 用于（13）CH4/（12）CH4 和 1.109-1.315 用于 CDH3/CH4。本实验中的当前值明显高于先前从海洋沉积物孔隙水中同位素特征分布估算的值，这与自然生境中 AOM 与其他过程的重叠一致。
