Microbial metabolism of hydrocarbons under methanogenic conditions

厌氧微生物是烃类生物降解的关键催化剂。目前对厌氧碳氢化合物代谢的了解主要来自在硝酸盐或硫酸盐还原条件下进行的研究，而在此类电子受体有限的产甲烷环境中，人们所知相对较少。 这些环境可能包括受污染的饮用水蓄水层和具有重要经济意义的储油层。 产甲烷菌是一组专门的微生物，它们只利用一些简单的化合物，如乙酸盐或氢气/二氧化碳来形成甲烷。因此，烃生物转化为甲烷需要其他物种的参与，这些物种可以酶促活化烃并将其代谢为产甲烷前体。 目前，烃活化机制，随后的代谢途径，以及参与种间相互作用的烃活化微生物物种与产甲烷菌在很大程度上是未知的。 所提出的工作将通过两个主要目标提供关于产甲烷烃代谢的急需的基本信息：（1）通过化学分析和分解代谢基因探测来鉴定模型单芳烃、烷烃和多环芳烃的产甲烷代谢期间产生的代谢物，和（2）通过分离产甲烷菌，定向培养真细菌，以及包括基于核酸的稳定同位素探测的分子生物学方法。 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。 了解产甲烷烃代谢具有重要的生态，经济和能源相关的应用，在加拿大的燃料污染的饮用水含水层的恢复，如何产甲烷财团转换轻油，以较低的价值重油的水库，以及如何这样的财团可以在原地产生清洁燃烧的天然气从石油剩余的边际油藏作为一种“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.