泥炭地中微生物产生长链正构烷烃和长链脂肪酸的速率及其潜在的古气候学研究意义

The most ubiquitous and prominent group of compounds of leaf waxes are long chain n-alkanes and fatty acids. Relative abundance of these molecular compositions as well as compound-specific carbon and hydrogen isotope ratios of leaf wax can provide important information for paleo-climatic and paleo-environmental reconstructions. Terrestrial or aquatic plants were considered (or assumed) as the major contributors to these lipids, which are preserved in sediment of peatland or terrestrial lakes. However, some studies show that some microorganisms (e.g. some species of fungi, algae, aerobic and anaerobic bacteria) can also produce these lipids. Until now，there is lack of knowledge regarding generation rates of long-chain alkyl-lipids of microbial origin in various environments. In this study we aim to address this question by designing a series of microbial incubation experiments in deuterium-enriched peat systems, and with different antibiotics to inhibit certain groups so that major groups of lipid producers can be determined. With molecular biological technique, we will study the generation rates of microbial long-chain n-alkanes and fatty acids in different peatland environments, and main microbial groups (fungi, algae, aerobic and anaerobic prokaryotes) that are responsible for these generations. We will then evaluate their possible paleoclimatic significance.

叶蜡长链正构烷烃和长链脂肪酸各同系物的相对含量，及其单体碳、氢同位素是重建古气候和古环境的重要指标。在很多研究中，对于保存在沉积物中的长链正构烷烃和长链脂肪酸被认为主要是来源于陆生或水生植物。然而一些研究显示，微生物（如某些真菌、藻类、好养和厌氧细菌）也可产生类似于植物叶蜡的长链正构烷烃和长链脂肪酸。但是至今为止，对于环境中微生物产生上述脂类的速率鲜有报道。本课题将采用重水氘同位素标定技术，以及多种抗生素组合对泥炭地中各类微生物进行混合模拟培养，结合现代分子生物学技术，探索不同泥炭地环境中总微生物，以及不同微生物类群（真菌、真核藻类、好氧和厌氧原核生物）产长链正构烷烃和长链脂肪酸的能力及速率，并初步评估其潜在的古气候学研究意义。

叶蜡长链正构烷烃和长链脂肪酸各同系物的相对含量、及其单体碳、氢同位素是重建古气候和古环境的重要指标。在很多研究中，对于保存在沉积物中的长链正构烷烃和长链脂肪酸被认为主要来源于陆生或水生植物。但迄今为止，对于环境中微生物产生上述脂类的速率研究鲜有报道。本项目旨在利用有机物单体氢同位素测试技术探索泥炭和森林土壤中微生物产生长链正构烷烃和长链脂肪酸的能力和速率，并评估其潜在的古气候学意义。研究结果显示有氧条件下，微生物产生的长链正构烷烃可以达到每年最多新增0.1%（相对于原来总的正构烷烃）。而在有氧和无氧两种条件下，微生物都可以产生短链(C18–C21)正构烷烃，且产生速率可以达到上至每年2.5%。这表明叶蜡在有氧条件的长期滞留不但可能使其遭受持续的降解作用，还可能会不断混入并积累微生物来源的长链正构烷烃，在利用沉积物中长链正构烷烃重建古气候时需要考虑到这一影响因素。

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