Long-chain (>C₂₅) n-alkyl lipids have long been considered biomarkers for higher plant leaf waxes and widely applied for paleoclimate and paleoenvironmental reconstructions. However, recent experimental and lacustrine sediment studies suggest long-chain n-alkanes and n-alkanoic acids can also be produced by aerobic microbes, probably heterotrophic microbes based on carbon isotope data. Here we show that sedimentary long-chain n-alkanes and n-alkanoic acids in two desolate Antarctic ponds where vascular plants are absent in the surroundings display hydrogen isotopic values up to 300 per mil higher than those of lake water. It is the first time that such strongly inverse or reduced hydrogen isotopic fractionation of lipid biomarkers is observed in natural sediment samples. Based on recent extensive experimental data on microbial hydrogen isotopic fractionation, our data can only be explained by the predominant production of long-chain n-alkanes and n-alkanoic acids from heterotrophic micro-organisms. Together with preliminary 16S rRNA gene sequencing data, our results represent the first unambiguous example of predominant heterotrophic microbial production of long-chain n-alkyl waxes in a natural environment.

中文翻译：

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逆氢同位素分馏表明在荒凉的南极池塘中异养微生物产生长链正烷基脂质

长链（>C ₂₅）正烷基脂质长期以来一直被认为是高等植物叶蜡的生物标志物，并广泛应用于古气候和古环境重建。然而，最近的实验和湖泊沉积物研究表明，长链正构烷烃和正构烷酸也可以由需氧微生物产生，根据碳同位素数据，可能是异养微生物。在这里我们展示了沉积的长链正构烷烃和n- 在两个荒凉的南极池塘中，周围没有维管植物的链烷酸显示出的氢同位素值比湖水高出高达 300/mil。这是第一次在天然沉积物样品中观察到脂质生物标志物的这种强烈的反向或减少的氢同位素分馏。基于最近关于微生物氢同位素分馏的大量实验数据，我们的数据只能通过异养微生物主要产生长链正构烷烃和正构烷酸来解释。连同初步的 16S rRNA 基因测序数据，我们的结果代表了长链n的主要异养微生物生产的第一个明确例子- 自然环境中的烷基蜡。