Unknown,Transcriptomics,Genomics,Proteomics

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L-Glutamine metabolism and its regulation in C. glutamicum

ABSTRACT: Corynebacterium glutamicum, a gram-positive soil bacterium used for the industrial production of amino acids such as L-glutamate and L-lysine, is able to use a number of different nitrogen sources, such as ammonium, urea, or creatinine. In this communication, we show that L-glutamine serves as an excellent nitrogen source for C. glutamicum and allows similar growth rates in glucose minimal medium as ammonium. A transcriptome comparison revealed a strong induction of the nitrogen starvation response when glutamine was used as nitrogen source. Subsequent growth experiments with a variety of mutants defective in nitrogen metabolism showed that glutamate synthase is crucial for glutamine utilization, while a putative glutaminase is dispensable under the experimental conditions used. The fact that the glutamate synthase encoding gltBD operon is under strict nitrogen control explains the necessity for induction of the nitrogen starvation response. The paradox situation that the nitrogen starvation response is induced although intracellular L-glutamine levels are high has implications on nitrogen sensing. In contrast to other gram-positive and gram-negative bacteria such as Bacillus subtilis, Salmonella typhimurium, and Klebsiella pneumoniae, a drop in glutamine concentration obviously does not serve as a nitrogen starvation signal in C. glutamicum. Three biological replicates were performed. To analyse how L-glutamine influences global gene expression when used as sole nitrogen source instead of ammonium, DNA microarray analyses were performed. For this purpose RNA was isolated from exponentially growing cells cultivated in CgXII medium containing glucose as carbon source and either L-glutamine or ammonium sulphate as nitrogen source.

ORGANISM(S): Corynebacterium glutamicum ATCC 13032

SUBMITTER: Andreas Burkovski

PROVIDER: E-GEOD-19779 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

L-Glutamine as a nitrogen source for Corynebacterium glutamicum: derepression of the AmtR regulon and implications for nitrogen sensing.

Rehm Nadine N Georgi Tobias T Hiery Eva E Degner Ursula U Schmiedl Alfred A Burkovski Andreas A Bott Michael M

Microbiology (Reading, England) 20100723 Pt 10

Corynebacterium glutamicum, a Gram-positive soil bacterium employed in the industrial production of various amino acids, is able to use a number of different nitrogen sources, such as ammonium, urea or creatinine. This study shows that l-glutamine serves as an excellent nitrogen source for C. glutamicum and allows similar growth rates in glucose minimal medium to those in ammonium. A transcriptome comparison revealed that the nitrogen starvation response was elicited when glutamine served as the ...[more]

PMID: 20656783

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Project description:The response regulator HrrA belonging to the HrrSA two-component system (previously named CgtSR11) is known to be repressed by the global iron-dependent regulator DtxR in Corynebacterium glutamicum. Sequence analysis indicated an involvement of the HrrSA system in heme-dependent gene expression. Growth experiments revealed that the non-pathogenic soil bacterium C. glutamicum is able to use hemin or hemoglobin as sole iron source. In DNA microarray analyses a putative operon encoding the hemin-binding protein HtaA and the putative hemin ABC transporter HmuTUV showed a strong upregulation in heme-grown cells. Deletion of the hmu operon clearly affects heme utilization, but does not completely abolish growth on heme or hemoglobin. As a central part of this study, we investigated the regulon of the response regulator HrrA via comparative transcriptome analysis of a hrrA deletion mutant and C. glutamicum wild type in combination with DNA-protein interaction studies with purified HrrA protein. Our data provide evidence for a heme-dependent transcriptional activation of heme oxygenase (hmuO), an enzyme involved in the utilization of heme as iron source. Besides hmuO, HrrA was shown to activate the expression of heme-containing components of the respiratory chain, namely ctaD and the ctaE-qcrCAB operon encoding subunits I and III of cytochrome aa3 oxidase and three subunits of the cytochrome bc1 complex. Furthermore, HrrA represses almost all genes involved in heme biosynthesis, including glutamyl-tRNA reductase (hemA), uroporphyrinogen decarboxylase (hemE), and ferrochelatase (hemH). Thus, our data clearly emphasize a central role of the HrrSA system in the control of heme homeostasis in C. glutamicum. Three biological replicates of each experiment were performed. Experiment 1: Transcriptome comparison of wild type grown und FeSO4 or heme as iron source; Exp. 2: WT vs. hrrA deletion mutant grown on FeSO4; Exp. 3: WT vs. hrrA mutant grown on heme. For analysis via DNA microarraysose RNA was isolated from exponentially growing cells cultivated in CgXII medium containing glucose as carbon source and either 2.5 uM FeSO4 or 2.5 uM heme as iron source.

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Dataset Information

L-Glutamine metabolism and its regulation in C. glutamicum

Publications

L-Glutamine as a nitrogen source for Corynebacterium glutamicum: derepression of the AmtR regulon and implications for nitrogen sensing.

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