Chakraborty R, Coates J D
Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720,USA.
Appl Microbiol Biotechnol. 2004 May;64(4):437-46. doi: 10.1007/s00253-003-1526-x. Epub 2004 Jan 21.
Over the last two decades significant advances have been made in our understanding of the anaerobic biodegradability of monoaromatic hydrocarbons. It is now known that compounds such as benzene, toluene, ethylbenzene, and all three xylene isomers can be biodegraded in the absence of oxygen by a broad diversity of organisms. These compounds have been shown to serve as carbon and energy sources for bacteria growing phototrophically, or respiratorily with nitrate, manganese, ferric iron, sulfate, or carbon dioxide as the sole electron acceptor. In addition, it has also been recently shown that complete degradation of monoaromatic hydrocarbons can also be coupled to the respiration of oxyanions of chlorine such as perchlorate or chlorate, or to the reduction of the quinone moieties of humic substances. Many pure cultures of hydrocarbon-degrading anaerobes now exist and some novel biochemical and genetic pathways have been identified. In general, a fumarate addition reaction is used as the initial activation step of the catabolic process of the corresponding monoaromatic hydrocarbon compounds. However, other reactions may alternatively be involved depending on the electron acceptor utilized or the compound being degraded. In the case of toluene, fumarate addition to the methyl group mediated by benzylsuccinate synthase appears to be the universal mechanism of activation and is now known to be utilized by anoxygenic phototrophs, nitrate-reducing, Fe(III)-reducing, sulfate-reducing, and methanogenic cultures. Many of these biochemical pathways produce unique extracellular intermediates that can be utilized as biomarkers for the monitoring of hydrocarbon degradation in anaerobic natural environments.
在过去二十年里，我们对单环芳烃厌氧生物降解性的理解取得了重大进展。现在已知，苯、甲苯、乙苯以及所有三种二甲苯异构体等化合物能够在无氧条件下被多种生物进行生物降解。这些化合物已被证明可作为细菌的碳源和能源，这些细菌通过光养生长，或以硝酸盐、锰、铁离子、硫酸盐或二氧化碳作为唯一电子受体进行呼吸作用。此外，最近还表明，单环芳烃的完全降解还可以与氯的含氧阴离子（如高氯酸盐或氯酸盐）的呼吸作用，或与腐殖质醌部分的还原作用相耦合。现在存在许多降解烃类的厌氧纯培养物，并且已经确定了一些新的生化和遗传途径。一般来说，富马酸加成反应被用作相应单环芳烃化合物分解代谢过程的初始激活步骤。然而，根据所利用的电子受体或被降解的化合物，可能会涉及其他反应。就甲苯而言，由苄基琥珀酸合酶介导的甲基富马酸加成似乎是普遍的激活机制，现在已知它被无氧光养生物、硝酸盐还原菌、铁（III）还原菌、硫酸盐还原菌和产甲烷培养物所利用。这些生化途径中的许多都会产生独特的细胞外中间体，这些中间体可作为生物标志物用于监测厌氧自然环境中的烃类降解。
