Unknown,Transcriptomics,Genomics,Proteomics

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Adaptation of Bacillus subtilis carbon core metabolism to simultaneous nutrient limitation and osmotic challenge

ABSTRACT: Here, we investigated for the first time the systems-wide response of B. subtilis to different simultaneous stresses, i.e. nutrient limitation and high osmolarity. To address the anticipated complexity of the cellular response networks, we combined chemostat experiments under conditions of carbon limitation, salt stress and osmoprotection with multi-omics analyses at the transcriptome, proteome, metabolome and fluxome levels. Our results indicate that the flux through central carbon and energy metabolism is very robust under all conditions studied. The key to achieve this robustness is the adjustment of the biocatalytic machinery to compensate for solvent-induced impairment of enzymatic activities during osmotic stress. The accumulation of the exogenously provided osmoprotectant glycine betaine helps the cell to rescue enzyme activities in the presence of high salt. A major effort of the cell during osmotic stress is the production of the compatible solute proline. This is achieved by the concerted adjustment of multiple reactions around the 2-oxoglutarate node, which drives metabolism towards the proline precursor glutamate. The fine-tuning of the transcriptional and metabolic networks involves functional modules that overarch the individual pathways. We applied transcriptomic, mass spectrometry-based protein, metabolite and 13C-metabolic flux analysis techniques to B. subtilis cells grown under well-controlled conditions in a glucose-limited chemostat at a growth rate of 0.1 h-1 under i) reference conditions, ii) in the presence of 1.2 M NaCl, and iii) in the presence of 1.2 M NaCl and 1 mM GB. Microarray hybridizations were performed with RNA from three biological replicates. The individual samples were labeled with Cy5; a reference pool containing equal amounts of RNA from all 9 samples was labeled with Cy3.

ORGANISM(S): Bacillus subtilis

SUBMITTER: Ulrike MM-CM-$der

PROVIDER: E-GEOD-53333 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Adaptation of Bacillus subtilis carbon core metabolism to simultaneous nutrient limitation and osmotic challenge: a multi-omics perspective.

Kohlstedt Michael M Sappa Praveen K PK Meyer Hanna H Maaß Sandra S Zaprasis Adrienne A Hoffmann Tamara T Becker Judith J Steil Leif L Hecker Michael M van Dijl Jan Maarten JM Lalk Michael M Mäder Ulrike U Stülke Jörg J Bremer Erhard E Völker Uwe U Wittmann Christoph C

Environmental microbiology 20140331 6

The Gram-positive bacterium Bacillus subtilis encounters nutrient limitations and osmotic stress in its natural soil ecosystem. To ensure survival and sustain growth, highly integrated adaptive responses are required. Here, we investigated the system-wide response of B. subtilis to different, simultaneously imposed stresses. To address the anticipated complexity of the cellular response networks, we combined chemostat experiments under conditions of carbon limitation, salt stress and osmoprotect ...[more]

PMID: 24571712

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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

Project description:Background: Microbial gene expression is to a large extend determined by environmental growth conditions. Differential gene expression analysis between two conditions has been frequently used to reveal regulatory networks and to assign physiological function to unknown genes. In nature, microorganisms cohabit however these interactions have been rarely studied and reproduced in laboratory set-up. Thus to quantitatively explore the genome-wide responses of microbial interaction, we co-cultivated Penicillium chrysogenum and Bacillus subtilis in chemostat culture. Results: Time course expression analysis of P. chrysogenum to co-cultivation with B. subtilis was carried out to understand the natural responses of P. chrysogenum to prokaryotes. Steady state chemostats of P. chrysogenum in non-B-lactam producing conditions was pulsed with B. subtilis and co-cultivation was followed for 72 hours. The dynamic physiological and transcriptional responses of P. chrysogenum in mixed culture were monitored. B. subtilis outcompeted growth of P. chrysogenum resulting in an increased B. subtilis biomass by more than three fold of its original size and a reduction in P. chrysogenum biomass to half of its original size after 72 h of mixed culture. Genes of the penicillin pathway, synthesis of the side-chain and precursors were overall unresponsive to the presence of B. subtilis. Moreover Penicillium polyketide synthase and nonribosomal peptide synthetase genes either remained silent or down-regulated, whereas genes responsible for protein synthesis, metabolism, energy conservation, respiration and transport were upregulated in the presence of B. subtilis. Among highly responsive genes, two putative B-1,3 endoglucanase (mutanase) genes viz Pc12g07500 and Pc12g13330 were upregulated by more than 15-fold and 8-fold respectively. Measurement of enzyme activity in the supernatant of mixed culture confirmed that the co-cultivation with B. subtilis induced mutanase production in P. chrysogenum. Mutanase activity was not observed in pure cultures of P. chrysogenum and B. subtilis or when P. chrysogenum was co-cultured with B. subtilis supernatant or heat inactivated B. subtilis cells. However, mutanase production was observed in cultures of P. chrysogenum pulsed with filter sterilized supernatants from mixed cultures P. chrysogenum and B. subtilis. Heterologous expression of Pc12g07500 and Pc12g13330 genes in Saccharomyces cerevisiae confirmed that at least Pc12g07500 encoded an B-1,3 endoglucanase. Conclusion: Time course transcriptional profiling of P. chrysogenum revealed several differentially expressed genes during mixed culture, potentially reflecting interactions between the eukaryotic and the prokaryotic systems. M-oM-^AM-!-1,3 endoglucanase produced by P. chrysogenum against B. subtilis signals may have application in improving the efficacy of antibiotics by degrading exopolysacchride biofilms of pathogenic bacteria. The objective of the present study is to investigate the response of P. chrysogenum to co-cultivation with B. subtilis. To trigger an interaction specific behaviour, steady state chemostat of P. chrysogenum Wisconsin 54-1255 was pulsed with B. subtilis. The dynamic, transcriptional and physiological responses of P. chrysogenum in mixed culture were monitored and analyzed. Several differentially expressed genes potentially reflected interactions between the eukaryotic and the prokaryotic systems. To test whether any bacterial signaling molecules are responsible for differential expression of selected fungal genes, P. chrysogenum cultures were inoculated with supernatant of B. subtilis culture, supernatants from mixed culture and with heat-inactivated B. subtilis. The specific transcriptional responses identified using microarray was verified by analysis of fermentation broth and functional characterization by expression of selected genes in S. cerevisiae.

Dataset Information

Adaptation of Bacillus subtilis carbon core metabolism to simultaneous nutrient limitation and osmotic challenge

Publications

Adaptation of Bacillus subtilis carbon core metabolism to simultaneous nutrient limitation and osmotic challenge: a multi-omics perspective.

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