Wöhlbrand Lars, Wilkes Heinz, Halder Thomas, Rabus Ralf
Max Planck Institute for Marine Microbiology, Bremen, Germany.
J Bacteriol. 2008 Aug;190(16):5699-709. doi: 10.1128/JB.00409-08. Epub 2008 Jun 6.
The denitrifying "Aromatoleum aromaticum" strain EbN1 was demonstrated to utilize p-ethylphenol under anoxic conditions and was suggested to employ a degradation pathway which is reminiscent of known anaerobic ethylbenzene degradation in the same bacterium: initial hydroxylation of p-ethylphenol to 1-(4-hydroxyphenyl)-ethanol followed by dehydrogenation to p-hydroxyacetophenone. Possibly, subsequent carboxylation and thiolytic cleavage yield p-hydroxybenzoyl-coenzyme A (CoA), which is channeled into the central benzoyl-CoA pathway. Substrate-specific formation of three of the four proposed intermediates was confirmed by gas chromatographic-mass spectrometric analysis and also by applying deuterated p-ethylphenol. Proteins suggested to be involved in this degradation pathway are encoded in a single large operon-like structure ( approximately 15 kb). Among them are a p-cresol methylhydroxylase-like protein (PchCF), two predicted alcohol dehydrogenases (ChnA and EbA309), a biotin-dependent carboxylase (XccABC), and a thiolase (TioL). Proteomic analysis (two-dimensional difference gel electrophoresis) revealed their specific and coordinated upregulation in cells adapted to anaerobic growth with p-ethylphenol and p-hydroxyacetophenone (e.g., PchF up to 29-fold). Coregulated proteins of currently unknown function (e.g., EbA329) are possibly involved in p-ethylphenol- and p-hydroxyacetophenone-specific solvent stress responses and related to other aromatic solvent-induced proteins of strain EbN1.
反硝化菌“芳香油假单胞菌”菌株EbN1已被证明在缺氧条件下能够利用对乙基苯酚，并且推测其采用的降解途径类似于同一细菌中已知的厌氧乙苯降解途径：对乙基苯酚首先羟基化生成1-(4-羟基苯基)乙醇，随后脱氢生成对羟基苯乙酮。可能随后的羧化和硫解裂解产生对羟基苯甲酰辅酶A（CoA），其进入中央苯甲酰辅酶A途径。通过气相色谱-质谱分析以及应用氘代对乙基苯酚，证实了四种推测中间体中的三种的底物特异性形成。推测参与该降解途径的蛋白质由一个单一的大操纵子样结构（约15 kb）编码。其中包括一种对甲酚甲基羟化酶样蛋白（PchCF）、两种预测的醇脱氢酶（ChnA和EbA309）、一种生物素依赖性羧化酶（XccABC）和一种硫解酶（TioL）。蛋白质组分析（二维差异凝胶电泳）显示，在适应以对乙基苯酚和对羟基苯乙酮进行厌氧生长的细胞中，它们特异性且协同上调（例如，PchF上调高达29倍）。目前功能未知的共调节蛋白（例如EbA329）可能参与对乙基苯酚和对羟基苯乙酮特异性的溶剂应激反应，并与菌株EbN1的其他芳香族溶剂诱导蛋白相关。
