Project description:DNA microarray experiments with phenylpropanoid pulses were performed in order to get hints on expression of relevant genes or gene clusters activated in presence of phenylpropanoid compounds. We determined the relative mRNA-levels of wild-type cells confronted with phenylpropanoids and unpulsed cells. A pulsing time of 30 minutes was sufficient to find regulation of gene expression in response to the phenylpropanoid amount of 5 mM (final concentration) added. A relatively short pulsing time was preferred over the cultivation of the strain with phenylpropanoids in comparison to growth on glucose because a completely different growth behavior was expected when using two completely unrelated carbon sources.
Project description:DNA microarray experiments with phenylpropanoid pulses were performed in order to get hints on expression of relevant genes or gene clusters activated in presence of phenylpropanoid compounds. We determined the relative mRNA-levels of wild-type cells confronted with phenylpropanoids and unpulsed cells. A pulsing time of 30 minutes was sufficient to find regulation of gene expression in response to the phenylpropanoid amount of 5 mM (final concentration) added. A relatively short pulsing time was preferred over the cultivation of the strain with phenylpropanoids in comparison to growth on glucose because a completely different growth behavior was expected when using two completely unrelated carbon sources.
Project description:Corynebacterium glutamicum ATCC 31831 grew on l-arabinose as the sole carbon source at a specific growth rate that was twice that on d-glucose. The gene cluster responsible for l-arabinose utilization comprised a six-cistron transcriptional unit with a total length of 7.8 kb. Three l-arabinose-catabolizing genes, araA (encoding l-arabinose isomerase), araB (l-ribulokinase), and araD (l-ribulose-5-phosphate 4-epimerase), comprised the araBDA operon, upstream of which three other genes, araR (LacI-type transcriptional regulator), araE (l-arabinose transporter), and galM (putative aldose 1-epimerase), were present in the opposite direction. Inactivation of the araA, araB, or araD gene eliminated growth on l-arabinose, and each of the gene products was functionally homologous to its Escherichia coli counterpart. Moreover, compared to the wild-type strain, an araE disruptant exhibited a >80% decrease in the growth rate at a lower concentration of l-arabinose (3.6 g liter(-1)) but not at a higher concentration of l-arabinose (40 g liter(-1)). The expression of the araBDA operon and the araE gene was l-arabinose inducible and negatively regulated by the transcriptional regulator AraR. Disruption of araR eliminated the repression in the absence of l-arabinose. Expression of the regulon was not repressed by d-glucose, and simultaneous utilization of l-arabinose and d-glucose was observed in aerobically growing wild-type and araR deletion mutant cells. The regulatory mechanism of the l-arabinose regulon is, therefore, distinct from the carbon catabolite repression mechanism in other bacteria.