Archaeal ANaerobic MEthanotrophs (ANME) facilitate the anaerobic oxidation of methane (AOM), a process that is believed to proceed via the reversal of the methanogenesis pathway. Carbon isotopic composition studies indicate that ANME are metabolically diverse and able to assimilate metabolites including methane, methanol, acetate, and dissolved inorganic carbon (DIC). Our data support the interpretation that ANME in marine sediments at methane seeps assimilate both methane and DIC, and the carbon isotopic compositions of the tetrapyrrole coenzyme F430 and the membrane lipids archaeol and hydroxy‐archaeol reflect their relative proportions of carbon from these substrates. Methane is assimilated via the methyl group of CH₃‐tetrahydromethanopterin (H₄MPT) and DIC from carboxylation reactions that incorporate free intracellular DIC. F430 was enriched in ¹³C (mean δ¹³C = −27‰ for Hydrate Ridge and −80‰ for the Santa Monica Basin) compared to the archaeal lipids (mean δ¹³C = −97‰ for Hydrate Ridge and −122‰ for the Santa Monica Basin). We propose that depending on the side of the tricarboxylic acid (TCA) cycle used to synthesize F430, its carbon was derived from 76% DIC and 24% methane via the reductive side or 57% DIC and 43% methane via the oxidative side. ANME lipids are predicted to contain 42% DIC and 58% methane, reflecting the amount of each assimilated into acetyl‐CoA. With isotope models that include variable fractionation during biosynthesis for different carbon substrates, we show the estimated amounts of DIC and methane can result in carbon isotopic compositions of − 73‰ to − 77‰ for F430 and − 105‰ for archaeal lipids, values close to those for Santa Monica Basin. The F430 δ¹³C value for Hydrate Ridge was ¹³C‐enriched compared with the modeled value, suggesting there is divergence from the predicted two carbon source models.

中文翻译：

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甲烷氧化古细菌中辅酶F430和膜脂的碳同位素异质性

古生厌氧甲烷营养菌（ANME）促进甲烷的厌氧氧化（AOM），该过程被认为是通过甲烷生成途径的逆转而进行的。碳同位素组成研究表明，ANME具有代谢多样性，能够吸收包括甲烷，甲醇，乙酸盐和溶解的无机碳（DIC）在内的代谢产物。我们的数据支持以下解释，即甲烷在海洋沉积物中的ANME会吸收甲烷和DIC，四吡咯辅酶F430的碳同位素组成以及膜脂质archaeol和羟基-archaeol反映了它们在这些底物中的相对碳含量。甲烷通过CH _3-四氢甲基蝶呤（H ₄MPT）和DIC结合游离细胞内DIC的羧化反应而得。F430在富集¹³ C（平均δ ¹³ C = -27‰，水合物脊和-80‰，在Santa Monica盆地）相比，古细菌脂质（平均δ ¹³水合物岭的C = −97‰，圣莫尼卡盆地的C = −122‰。我们建议，取决于用于合成F430的三羧酸（TCA）循环的一面，其碳是通过还原性一面由76％DIC和24％甲烷或通过氧化一面衍生自57％DIC和43％甲烷。预计ANME脂质包含42％的DIC和58％的甲烷，反映出每种被乙酰基-CoA吸收的量。使用包括在不同碳底物生物合成过程中可变分馏的同位素模型，我们显示出DIC和甲烷的估计量可导致F430的碳同位素组成为-73‰至-77‰，而古生脂质的碳同位素组成为-105‰，其值接近圣莫尼卡盆地的那些。在F430δ ¹³为水合物脊C值是¹³与模型值相比，C富集，表明与预测的两个碳源模型存在差异。