Department of Biology, University of Konstanz, Universitätsstr. 10, D-78457 Konstanz, Germany.
Environ Microbiol Rep. 2012 Oct;4(5):469-78. doi: 10.1111/j.1758-2229.2011.00304.x. Epub 2011 Nov 27.
Mononuclear aromatic compounds are degraded anaerobically through pathways that are basically different from those used in the presence of oxygen. Whereas aerobic degradation destabilizes the aromatic π-electron system by oxidative steps through oxygenase reactions, anaerobic degradation is most often initiated by a reductive attack. The benzoyl-CoA pathway is the most important metabolic route in this context, and a broad variety of mononuclear aromatics, including phenol, cresols, toluene, xylenes and ethylbenzene, are channelled into this pathway through various modification reactions. Multifunctional phenolic compounds are metabolized via the reductive resorcinol pathway, the oxidative resorcinol pathway with hydroxyhydroquinone as key intermediate, and the phloroglucinol pathway. Comparison of the various pathways used for modification and degradation of aromatics in the absence of oxygen indicates that the strategies of breakdown of these compounds are largely determined by the redox potentials of the electron acceptors used, and by the overall reaction energetics. Consequently, nitrate reducers quite often use strategies for primary attack on aromatic compounds that differ from those used by sulfate-reducing, iron-reducing or fermenting bacteria.
单核芳香族化合物在无氧条件下通过与有氧条件下基本不同的途径进行降解。虽然有氧降解通过加氧酶反应的氧化步骤使芳香π-电子系统失稳，但无氧降解通常是由还原攻击引发的。在这种情况下，苯甲酰辅酶 A 途径是最重要的代谢途径，通过各种修饰反应，包括苯酚、甲酚、甲苯、二甲苯和乙苯在内的多种单核芳烃都被导入该途径。多官能酚类化合物通过还原间苯二酚途径、以羟基氢醌为关键中间体的氧化间苯二酚途径和间苯三酚途径进行代谢。比较无氧条件下芳烃修饰和降解所使用的各种途径表明，这些化合物的分解策略在很大程度上取决于所使用的电子受体的氧化还原电位以及总体反应能量学。因此，硝酸盐还原菌通常使用与硫酸盐还原菌、铁还原菌或发酵菌不同的策略来对芳香族化合物进行初次攻击。
