Natural anaerobic degradation of methane and petroleum in marine sediments: geochemical gradients, degradation succession and microbial zonation

石油是碳氢化合物和其他有机物质的复杂混合物。在碳氢化合物中，烷烃、环烷烃和各种芳香族化合物占很大比例。在海洋环境中，石油通过深层储集层的沉积物自然迁移，通过不同的氧化还原水平、电子受体和微生物降解过程的区域。因此，可降解的碳化合物从氧化还原级联的能量下端，即从还原区域进入微生物活性区域，与从水柱沉积的溢油相反，即从氧化的顶部。因此，沉积物中天然石油降解的顺序是从厌氧过程开始，通过利用不同的电子受体“以相反的顺序”结束，以好氧呼吸结束。鉴于这一流动方向，我们预计石油组分的自然降解序列将不同于传统的实验室实验，这些实验集中在选定的生物或浓缩培养物的降解能力上。该项目的主要目标是研究来自不同海洋位置的完整沉积物岩心中微生物降解石油的演替情况，模拟从底部渗漏石油和从沉积物顶部溢出石油这两种情况。此外，还将探讨在石油存在下甲烷厌氧氧化的性能。将利用地球化学和分子方法来解决石油逐步垂直降解的问题，并确定负责的微生物。

Petroleum is a complex mixture of hydrocarbons and other organic substances. Amongst the hydrocarbons, alkanes, cycloalkanes, and various aromatic compounds make up a large fraction. In the marine environment, petroleum naturally migrates through sediments from deeper reservoirs, passing different redox levels, electron acceptors and zones of microbial degradation processes. Thereby degradable carbon compounds enter the microbially active zone from the energetically lower end of the redox cascade, i.e., from the reduced zone, in opposite to oil spills that settle from the water column, i.e., from the oxygenated top. Consequently, the order of natural petroleum degradation in sediments starts with anaerobic processes through the utilization of different electron acceptors 'in reverse order' and ends with aerobic respiration. Given this flow direction, we expect the natural degradation succession of petroleum components to differ from conventional lab experimentations that concentrate on the degradation ability of selected organisms or enrichment cultures. The main objective of this project is to investigate the succession of microbial petroleum degradation in intact sediment cores from different marine locations simulating both situations: petroleum seepage from below and oil spill from top of the sediment. In addition, the performance of anaerobic oxidation of methane in the presence of petroleum will be explored. Geochemical and molecular methods will be applied to resolve the step-wise vertical degradation of petroleum and to identify the responsible microorganism.