Substrat-spezifische Induktion der anaeroben Abbauwege von aromatischen Verbindungen in Aromatoleum aromaticum EbN1

The facultative anaerobic denitrifying bacterium Aromatoleum aromaticum EbN1 is able to distinctively degrade aromatic hydrocarbons and phenolic compounds anaerobically. This trait was surprising in comparison to aerobic degraders like Pseudomonas putida and revealed the interesting field of anoxic degradation of environmental pollution in deep soil. The genetic accessibility makes Aromatoleum aromaticum EbN1 a desirable model organism for the understanding of distinct anaerobic metabolism. Even more, the anoxic degradation of the very similar compounds toluene, ethylbenzene, phenol, and p-ethylphenol is separately regulated for each substrate. Based on earlier experiments, sequence alignments and similarities to other hydrocarbon degrading organisms, putative regulators have been assigned to the different degradation clusters. It was proposed that toluene, ethylbenzene, and acetophenone degradation in Aromatoleum aromaticum EbN1 are under the control of the two component systems tdiRS, ediRS and adiRS respectively. In contrast, σ54 dependent regulators are probably responsible for the activation of the degradation of 4-ethylphenol (EtpR) and phenol (PdeR). All of these proposed regulators are coded in genes directly adjacent to the respective degradation operon. In this study the proposed functions of EtpR and PdeR were investigated. Thereby, two disruption mutants were designed and examined in their growth phenotyp. It seems that the proposed thesis is correct and the genes etpR and pdeR code for activators of the respective operons. Furthermore, first studies were started to determine the inductors of 4-ethylphenol- and phenol operon as well as to identify transcriptional starts and operator binding sites. Recent results show a complex network of interactions between the distinct pathways to degrade 4-ethylphenol and ethylbenzene and their postulated regulation systems. To gain further insight into the matter, Aromatoleum aromaticum EbN1 was cultivated with different carbon sources and the method of RNA-Sequencing using reverse transcription was established. The isolated and enriched mRNA from these cultures was analyzed in this high-throughput approach by Illumina sequencing. Not only was new light shed on the complexity of the regulation network, but also new hints were given concerning the unknown steps in the different degradation pathways.