Pathway diversity and stereochemistry of anaerobic degradation of alkyltoluenes/-benzoates

烷基苯广泛存在于原油和各种石油产品中。它们在受污染的含水层或油藏等缺氧自然生境中的生物降解对这些有害有机化合物的环境命运起着重要作用。在过去的20年中，已经分离和鉴定了几种能够利用烷基苯作为碳和能量的唯一来源的反硝化、铁还原和硫酸盐还原细菌。甲苯一直是研究芳烃厌氧降解的典型模型化合物。甲苯的厌氧氧化是由其加入富马酸酯引发的，产生苄基琥珀酸盐作为初始活化产物。然后，琥珀酸苄酯转化为苯甲酰辅酶a，这是许多芳香族化合物厌氧分解代谢的中心聚合中间体。苯甲酰辅酶a通过环还原、开环和-氧化完全氧化为二氧化碳。尽管有相当数量的细菌分离物可以利用这些底物，但对烷基甲苯和相关的烷基苯甲酸酯的降解途径知之甚少。在这个项目中，我们将研究厌氧生物降解烷基甲苯/苯甲酸酯的途径多样性和立体化学，特别关注对异构体。酶反应和降解途径将通过鉴定鉴定的蛋白质的预测功能和相应的代谢物的鉴定来提出。

Alkylbenzenes occur widely in crude oil and various petroleum products. Their biodegradation in anoxic natural habitats such as contaminated aquifers or petroleum reservoirs plays an important role with respect to the environmental fate of these hazardous organic compounds. During the last 20 years several denitrifying, iron-reducing and sulfate-reducing bacteria capable of utilising alkylbenzenes as sole source of carbon and energy have been isolated and characterised. Toluene has been the archetypal model compound to study the anaerobic degradation of aromatic hydrocarbons. The well-established anaerobic oxidation of toluene is initiated by its addition to fumarate yielding benzylsuccinate as initial activation product. Benzylsuccinate is then transformed to benzoyl-CoA, the central convergent intermediate in anaerobic catabolism of many aromatic compounds. Complete oxidation of benzoyl-CoA to carbon dioxide proceeds via ring reduction, ring opening and -oxidation. Only little is known about the degradation pathways of alkyltoluenes and related alkylbenzoates, despite a considerable number of bacterial isolates that can utilize these substrates. In this project we will investigate the pathway diversity and stereochemistry of anaerobic biodegradation of alkyltoluenes/-benzoates with a specifc focus on the para-isomers. Enzymatic reactions and degradation pathways will be proposed by underpinning predicted functions of identified protein with the identification of the corresponding metabolites.