Hristova Krassimira R, Schmidt Radomir, Chakicherla Anu Y, Legler Tina C, Wu Janice, Chain Patrick S, Scow Kate M, Kane Staci R
Department of Land Air and Water Resources, Plant and Environmental Sciences Building, University of California, Davis, Davis, CA 95616.
Appl Environ Microbiol. 2007 Nov;73(22):7347-57. doi: 10.1128/AEM.01604-07. Epub 2007 Sep 21.
High-density whole-genome cDNA microarrays were used to investigate substrate-dependent gene expression of Methylibium petroleiphilum PM1, one of the best-characterized aerobic methyl tert-butyl ether (MTBE)-degrading bacteria. Differential gene expression profiling was conducted with PM1 grown on MTBE and ethanol as sole carbon sources. Based on microarray high scores and protein similarity analysis, an MTBE regulon located on the megaplasmid was identified for further investigation. Putative functions for enzymes encoded in this regulon are described with relevance to the predicted MTBE degradation pathway. A new unique dioxygenase enzyme system that carries out the hydroxylation of tert-butyl alcohol to 2-methyl-2-hydroxy-1-propanol in M. petroleiphilum PM1 was discovered. Hypotheses regarding the acquisition and evolution of MTBE genes as well as the involvement of IS elements in these complex processes were formulated. The pathways for toluene, phenol, and alkane oxidation via toluene monooxygenase, phenol hydroxylase, and propane monooxygenase, respectively, were upregulated in MTBE-grown cells compared to ethanol-grown cells. Four out of nine putative cyclohexanone monooxygenases were also upregulated in MTBE-grown cells. The expression data allowed prediction of several hitherto-unknown enzymes of the upper MTBE degradation pathway in M. petroleiphilum PM1 and aided our understanding of the regulation of metabolic processes that may occur in response to pollutant mixtures and perturbations in the environment.
高密度全基因组cDNA微阵列被用于研究嗜油甲基杆菌PM1（一种特性最佳的好氧甲基叔丁基醚（MTBE）降解菌）的底物依赖性基因表达。以MTBE和乙醇作为唯一碳源培养PM1，进行差异基因表达谱分析。基于微阵列高分和蛋白质相似性分析，鉴定出位于大质粒上的一个MTBE调控子以进行进一步研究。描述了该调控子中编码的酶的假定功能及其与预测的MTBE降解途径的相关性。发现了一种新的独特双加氧酶系统，该系统在嗜油甲基杆菌PM1中可将叔丁醇羟基化为2-甲基-2-羟基-1-丙醇。提出了关于MTBE基因的获得和进化以及IS元件在这些复杂过程中的作用的假设。与以乙醇为碳源培养的细胞相比，在以MTBE为碳源培养的细胞中，分别通过甲苯单加氧酶、苯酚羟化酶和丙烷单加氧酶进行的甲苯、苯酚和烷烃氧化途径上调。九个假定的环己酮单加氧酶中有四个在以MTBE为碳源培养的细胞中也上调。这些表达数据有助于预测嗜油甲基杆菌PM1中MTBE降解途径上游的几种未知酶，并有助于我们理解可能因污染物混合物和环境扰动而发生的代谢过程的调控。
