Microbial metabolism of hydrocarbons under methanogenic conditions

厌氧微生物是目前已知的碳氢化合物生物降解的关键催化剂。目前关于厌氧碳氢化合物代谢的知识主要来自于硝酸盐或硫酸盐还原条件下的研究，而在产甲烷环境中所知的相对较少，因为这种电子受体是有限的。这些环境可能包括受污染的饮用水含水层和经济上重要的油藏。产甲烷菌是一种特殊的微生物群，它们只利用一些简单的化合物，如醋酸盐或氢/二氧化碳来形成甲烷。因此，碳氢化合物向甲烷的生物转化需要其他物种的参与，这些物种可以酶激活碳氢化合物并将其代谢为产甲烷的前体。目前，烃类的活化机制、随后的代谢途径以及与产甲烷菌相互作用的烃类活化微生物种类在很大程度上是未知的。该工作将通过两个主要目标(1)通过化学分析和分解代谢基因探测，确定模型单芳烃、烷烃和多环芳烃在产甲烷代谢过程中产生的代谢物；(2)通过分离产甲烷菌，确定参与碳氢化合物生物转化的关键厌氧微生物物种。真细菌的定向培养和分子生物学方法，包括基于核酸的稳定同位素探测。通过这项工作，将确定产甲烷烃代谢的关键生物和生化途径。了解产甲烷烃代谢在加拿大具有重要的生态、经济和能源相关应用，包括恢复受燃料污染的饮用水含水层，产甲烷联合体如何将储层中的轻油转化为低价值的重油，以及如何利用这些联合体从边缘储层的剩余油中就地生产清洁燃烧的天然气，作为一种“绿色”能源回收生物技术。

Anaerobic microorganisms are now known to be key catalysts of hydrocarbon biodegradation. The current knowledge of anaerobic hydrocarbon metabolism comes mainly from studies conducted under nitrate- or sulfate-reducing conditions, while comparatively little is known in methanogenic environments where such electron acceptors are limited. These environments can include polluted drinking water aquifers and economically important oil reservoirs. Methanogens are a specialized group of microorganisms that utilize only a few simple compounds such as acetate or hydrogen/carbon dioxide to form methane. Thus, hydrocarbon bioconversion to methane requires the participation of other species that can enzymatically activate a hydrocarbon and metabolize it to methanogenic precursors. Currently, the hydrocarbon activation mechanisms, the ensuing metabolic pathways, and the hydrocarbon-activating microbial species involved in the interspecies interaction with methanogens are largely unknown. The proposed work will provide much needed fundamental information regarding methanogenic hydrocarbon metabolism through two major objectives (1) identifying metabolites produced during the methanogenic metabolism of model monoaromatic hydrocarbons, alkanes, and polycyclic aromatic hydrocarbons through chemical analysis and catabolic gene probing, and (2) identifying key anaerobic microbial species involved in the bioconversion of hydrocarbons through the isolation of methanogens, directed cultivation of eubacteria, and molecular biology methods including nucleic acid-based stable isotope probing. Through this work, key organisms and biochemical pathways of methanogenic hydrocarbon metabolism will be identified. Understanding methanogenic hydrocarbon metabolism has important ecological, economic, and energy-related applications in Canada with respect to the restoration of fuel-contaminated drinking water aquifers, how methanogenic consortia convert light oil to lower-value heavy oil in reservoirs, and how such consortia may be used in situ to generate clean-burning natural gas from oil remaining in marginal reservoirs as a "green" energy recovery biotechnology.