This title appears in the Scientific Report :
2006
MtrA, ein bifunktionaler Antwortregulator aus $\textit{Corynebacterium glutamicum}$
MtrA, ein bifunktionaler Antwortregulator aus $\textit{Corynebacterium glutamicum}$
The membrane-bound sensor kinase MtrB and the response regulator MtrA form one of 13 two-component systems in the gram-positive soil bacterium $\textit{Corynebacterium glutamicum}$. The MtrAB system is highly conserved in actinomycetes and therefore presumably plays an important role in the adaptati...
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Personal Name(s): | Brocker, Melanie (Corresponding author) |
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Contributing Institute: |
Biotechnologie 1; IBT-1 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2006
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Physical Description: |
VI, 125 S. |
Dissertation Note: |
Universität Düsseldorf, Diss., 2006 |
ISBN: |
978-3-89336-561-6 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
Biotechnologie |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Gesundheit / Health
11 |
Subject (ZB): | |
Publikationsportal JuSER |
The membrane-bound sensor kinase MtrB and the response regulator MtrA form one of 13 two-component systems in the gram-positive soil bacterium $\textit{Corynebacterium glutamicum}$. The MtrAB system is highly conserved in actinomycetes and therefore presumably plays an important role in the adaptation of these bacteria to the environment. In this work the function of the MtrAB system was studied by the analysis of different mutant strains and by the identification of direct target genes of MtrA. The following results were obtained: 1. Cells of a $\Delta \textit{mtrAB}$ mutant showed an abnormal morphology and an altered antibiotics susceptibility. They were more sensitive to penicillin, vancomycin and lysozyme but more resistant to ethambutol. A comparable phenotype was observed for $\Delta \textit{mtrA}$ and $\Delta \textit{mtrB}$ mutants. Only the sensitivity of $\Delta \textit{mtrB}$ to ethambutol was comparable to that of the wild type. 2. Transcriptome comparisons with DNA microarrays disclosed genes with an altered mRNA level in the $\Delta \textit{mtrAB}$ and the $\Delta \textit{mtrA}$ mutant. Amongst others, the mRNA concentration of $\textit{mepA}$ and $\textit{nlpC}$, encoding cell wall peptidases, was increased whereas the mRNA level of $\textit{betP}$ and $\textit{proP}$, encoding importers for betaine and proline, respectively, was decreased. 3. Deletion of $\textit{mepA}$ or $\textit{ppmA}$ in the $\Delta \textit{mtrAB}$ mutant resulted in strains with the same morphology, growth behaviour and antibiotics susceptibility as $\Delta \textit{mtrAB}$. Thus, elevated expression of $\textit{mepA}$ or $\textit{ppmA}$ alone is not responsible for the phenotype of the $\Delta \textit{mtrAB}$ strain. 4. To identify direct target genes of the response regulator MtrA, ChIP-to-chip-analysis, DNA affinity chromatography and gel retardation assays were performed. With latter method, the MtrA binding sites in the promoter regions of $\textit{nlpC}$, $\textit{mepA}$, $\textit{proP}$ and $\textit{betP}$ were determined. The binding sites upstream of the repressed genes $\textit{mepA}$ and $\textit{nlpC}$ overlap with the “-10” region, whereas those upstream of the activated genes $\textit{betP}$ and $\textit{proP}$ are located more than 40 bp upstream of the transcriptional start sites. The in vitro affinity of unphosphorylated MtrA to repressed genes was twofold higher compared to activated genes. 5. The identified binding sites in the promoter regions of $\textit{mepA}$, $\textit{nlpC}$, $\textit{betP}$ and $\textit{proP}$ were used to derive a consensus motif. A search for this motif within the $\textit{C. glutamicum}$ genome and further gel retardation assays revealed 12 additional promoter regions to which MtrA binds, e.g. the promoter region of $\textit{ppmA}$ (putative protease-modulator), $\textit{csbD}$ (putative stress induced protein), $\textit{katA}$ (catalase), $\textit{rpf2}$ (growth factor) and $\textit{dnaA}$ (replication initiation protein). 6. The majority of genes activated by MtrA are involved in different types of stress, e.g. $\textit{betP}$ and $\textit{proP}$ in hyperosmotic stress or $\textit{katA}$ in oxidative stress. Genes repressed by MtrA encode, among others, three putative cell wall peptidases ($\textit{mepA}$, $\textit{nlpC}$, $\textit{mepB}$) and a growth factor ($\textit{rpf2}$). Moreover MtrA binds to some genes (e. g. dnaA) that showed no altered expression in the microarray experiments. These observations suggest that the MtrAB system may play a role in the coordination of stress responses, cell division and growth. |