Project description:Comparative transcriptome analysis of Methylibium petroleiphilum PM1 exposed to the fuel-oxygenates methyl-tert-butyl ether and ethanol 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 TBA to 2-methyl-2-hydroxy-1-propanol in M. petroleiphilum PM1 was discovered. Based on the expression data, 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, alkane monooxygenase as well as 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 global transcriptome response revealed the link between metabolism of MTBE and aromatic compounds (e.g. benzene, toluene) present in gasoline mixtures. The expression data aids our understanding of the regulation of metabolic processes that may occur in response to pollutant mixtures and perturbations in the environment. Keywords: bacterial metabolism
