Unknown,Transcriptomics,Genomics,Proteomics

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Gene regulation in Bacillus subtilis by the compatible solute glycine betaine

ABSTRACT: Glycine betaine (GB) is a potent osmoprotectant for salt stressed Bacillus subtilis cells, which possess three high-affinity uptake systems for GB. OpuA is the dominant transporter for this compatible solute. Northern blot analysis, primer extension experiments and opuA-treA reporter gene fusion studies demonstrated that opuA expression is strongly induced at high osmolality from a single SigA-type promoter. Promoter mutations that improve the match of the opuA promoter to the consensus sequence substantially increase basal-level expression but reduce inducibility by high salinity. Expression of opuA is sensitively controlled by GB, which causes significant repression of opuA transcription at low and high salinity. GB influences the kinetics as well as the final level of high salinity induction of opuA in a concentration-dependent fashion. The repressing effect of GB on opuA transcription requires the intracellular presence of GB, regardless whether it is taken up via OpuA or other transporters or synthesized from choline. Genome-wide transcriptional profiling of salt-stressed B. subtilis cells demonstrated that the repressive effect of GB targets only a subset of high-salinity induced genes. This group of GB-responsive genes comprises in essence the full set of genes with demonstrated functions in either the uptake or synthesis of compatible solutes. Four different samples (untreated, GB, NaCl, and GB + NaCl treated) were analyzed and each sample was hybridized in triplicate.

ORGANISM(S): Bacillus subtilis

SUBMITTER: Annette Wensing

PROVIDER: E-GEOD-17435 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Global transcriptional profiling of Bacillus subtilis cells comparing wild-type to a ccpN (yqzB) non polar mutant. Abstract of associated publication (article accepted): The transcriptional regulator CcpN of Bacillus subtilis has been recently characterized as a repressor of two gluconeogenic genes, gapB and pckA, and of a small non-coding regulatory RNA, sr1, involved in arginine catabolism. Deletion of ccpN impairs growth on glucose and strongly alters the distribution of intracellular fluxes, rerouting the main glucose catabolism from glycolysis to the pentose phosphate (PP) pathway. Using transcriptome analysis, we show that during growth on glucose, gapB and pckA are the only protein-coding genes directly repressed by CcpN. By quantifying intracellular fluxes in deletion mutants, we demonstrate that derepression of pckA under glycolytic condition causes the growth defect observed in the ccpN mutant due to extensive futile cycling through the pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and pyruvate kinase. Beyond ATP dissipation via this cycle, PckA activity causes a drain on tricarboxylic acid cycle intermediates, which we show to be the main reason for the reduced growth of a ccpN mutant. The high flux through the PP pathway in the ccpN mutant is modulated by the flux through the alternative glyceraldehyde-3-phosphate dehydrogenases, GapA and GapB. Strongly increased concentrations of intermediates in upper glycolysis indicate that GapB overexpression causes a metabolic jamming of this pathway and, consequently, increases the relative flux through the PP pathway. In contrast, derepression of sr1, the third known target of CcpN, plays only a marginal role in ccpN mutant phenotypes. Two-condition experiment, wt vs. ccpN mutant. 4 experiments were performed different days with 3 independent RNA preparations (from separate cultures) and 3 independent sets of macroarrays: Experiment 1 (samples wt1 and ccpN1): total RNA extract1 / membranes set A Expereince 2 (samples wt2 and ccpN2): total RNA extract 2 / membranes set A Experiment 3 (samples wt2 and ccpN2): total RNA extract 3 / membranes set B Experiment 4 (samples wt2 and ccpN2): total RNA extract 3 / membranes set C

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Gene regulation in Bacillus subtilis by the compatible solute glycine betaine

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