Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

BW25113 glucose to acetate transition

ABSTRACT: In bacterial adaptation to the dynamic environment, metabolic genes are typically thought to be the executors, whereas global transcription regulators are regarded as the decision makers. Although the feedback from metabolic consequence is believed to be important, much less is understood. This work demonstrates that the gluconeogenic genes in Escherichia coli, ppsA, sfcA, and maeB, provide a feedback loop to the global regulator, CRP, in carbon source transition. Disruption of one of the gluconeogenic pathways has no phenotype in balanced growth, but causes a significant delay in the diauxic transition from glucose to acetate. To investigate the underlying mechanism, we measured the transcriptome profiles during the transition using DNA microarray, and Network Component Analysis was employed to obtain the transcription factor activities. Results showed that one of the global regulators, CRP, was insufficiently activated during the transition in the ppsA deletion mutant. Indeed, addition of cAMP partially rescued the delay in transition. These results suggest that the gluconeogenic flux to phosphoenolpyruvate is important for full activation of adenylate cyclase through phosphorylated enzyme IIAglu of the phosphotransferase system. Reduction of this flux causes insufficient activation of CRP and a global metabolic deficiency, which exemplifies a significant feedback interaction from metabolism to the global regulatory system. Keywords: Time course Cells were grown up in M9 glucose media until mid log phase, then harvested and transitioned into M9 acetate media. Samples were taken immediately prior to transition to acetate (reference sample) and at 5, 15, 30, 60, 120, 180, 240, 300, and 360 minutes after transition.

ORGANISM(S): Escherichia coli

SUBMITTER: Katy Kao

PROVIDER: E-GEOD-3250 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

A global regulatory role of gluconeogenic genes in Escherichia coli revealed by transcriptome network analysis.

Kao Katy C KC Tran Linh M LM Liao James C JC

The Journal of biological chemistry 20050831 43

In bacterial adaptation to the dynamic environment, metabolic genes are typically thought to be the executors, whereas global transcription regulators are regarded as the decision makers. Although the feedback from metabolic consequence is believed to be important, much less is understood. This work demonstrates that the gluconeogenic genes in Escherichia coli, ppsA, sfcA, and maeB, provide a feedback loop to the global regulator, cAMP receptor protein (CRP), in carbon source transition. Disrupt ...[more]

PMID: 16141204

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Project description:This is the model described in: Bacterial adaptation through distributed sensing of metabolic fluxes Oliver Kotte, Judith B Zaugg and Matthias Heinemann;Mol Sys Biol2010;6:355. doi:10.1038/msb.2010.10; Abstract: The recognition of carbon sources and the regulatory adjustments to recognized changes are of particular importance for bacterial survival in fluctuating environments. Despite a thorough knowledge base of Escherichia coli's central metabolism and its regulation, fundamental aspects of the employed sensing and regulatory adjustment mechanisms remain unclear. In this paper, using a differential equation model that couples enzymatic and transcriptional regulation of E. coli's central metabolism, we show that the interplay of known interactions explains in molecular-level detail the system-wide adjustments of metabolic operation between glycolytic and gluconeogenic carbon sources. We show that these adaptations are enabled by an indirect recognition of carbon sources through a mechanism we termed distributed sensing of intracellular metabolic fluxes. This mechanism uses two general motifs to establish flux-signaling metabolites, whose bindings to transcription factors form flux sensors. As these sensors are embedded in global feedback loop architectures, closed-loop self-regulation can emerge within metabolism itself and therefore, metabolic operation may adapt itself autonomously (not requiring upstream sensing and signaling) to fluctuating carbon sources. In its current form this SBML model is parametrized for the glucose to acetate transition and to simulate the extended diauxic shift as shown in figure 3 and scenario 6 of the attached matlab file. In this scenario the cells first are grown from an OD600 (BM) of 0.03 with a starting glucose concentration of 0.5 g/l for 8.15 h (29340 sec). Then a medium containing 5 g/l acetate is inoculated with these cells to an OD600 of 0.03 and grown for another 19.7 hours (70920 sec). Finally the cells are shifted to a medium containing both glucose and acetate at a concentration of 3 g/l with a starting OD600 of 0.0005. The shifts where implemented using events triggering at the times determined by the parameters shift1 and shift2 (in hours). To simulate other scenarios the initial conditions need to be changed as described in the supplemental materials (supplement 1) The original SBML model and the MATLAB file used for the calculations can be down loaded as supplementary materials of the publication from the MSB website. (supplement 2). The units of the external metabolites are in [g/l], those of the biomass in optical density,OD600, taken as dimensionless, and [micromole/(gramm dry weight)] for all intracellular metabolites. As the latter cannot be implemented in SBML, it was chosen to be micromole only and the units of the parameters are left mostly undefined. This model originates from BioModels Database: A Database of Annotated Published Models. It is copyright (c) 2005-2010 The BioModels Team.For more information see the terms of use.To cite BioModels Database, please use Le Novère N., Bornstein B., Broicher A., Courtot M., Donizelli M., Dharuri H., Li L., Sauro H., Schilstra M., Shapiro B., Snoep J.L., Hucka M. (2006) BioModels Database: A Free, Centralized Database of Curated, Published, Quantitative Kinetic Models of Biochemical and Cellular Systems Nucleic Acids Res., 34: D689-D691.

Project description:Microbially-mediated uranium bioremediation has been demonstrated in uranium contaminated aquifers when acetate was artificially supplied and growth of the natural population of Geobacteraceae was stimulated. In order to mimic the environmental response to acetate, steady-state cells of G. sulfureducens were cultured in chemostats under conditions of either 1) acetate as the sole electron donor and limiting factor and fumarate as the sole electron acceptor or 2) acetate was supplied in excess with fumarate as sole electron acceptor and limiting factor. In silico fluxome modeling and transcriptome analysis were used as tools for investigating the cell response to the acetate availability. For global gene expression profiling, a DNA microarray of the complete G. sulfurreducens genome was used. Statistically significant results were obtained from two-color, dye swap hybridizations produced from a total of three biological replicates. Eight technical replicates were tested from two of the biological replicates and six technical replicates were tested from the third biological replicate. Major findings from this study are given as follows. The in silico model successfully predicted a higher TCA-cycle flux (ca. 2-fold) under acetate-excess conditions, suggesting that catabolism of acetate is favored with respect to anabolism, and thus more electrons are available for metal reduction. Transcriptome analyses offered a comprehensive picture of the regulation points subjected to the acetate availability. Under acetate-excess conditions, acetate transporters in the G. sulfurreducens genome were down-regulated. In addition the oxidation-related acetyl-CoA transferase was up-regulated approximately three-fold and the assimilatory-related acetate kinase was down-regulated approximately two-fold, respectively, indicating that the transcriptional regulation of acetate activation may be the key point for coping with the excess of acetate and increasing the TCA flux. The level of transcription for 10 c-type cytochromes was significantly increased in cells cultured with an excess of acetate. OmcS, an outer-membrane cytochrome which actively participates in electron transfer to Fe(III)-oxides and graphite electrodes from fuel cells, showed one of the highest fold increases in transcription. The integration of in silico modeling and genome-wide analysis shows for first time how G. sulffureducens adapts its metabolic flux and transcriptional network for optimizing the use of acetate as an electron donor for exocellular respiration instead of for use as a carbon source for biomass production. Keywords: Geobacter, gene expression, acetate limitation, fumarate limitation

Dataset Information

BW25113 glucose to acetate transition

Publications

A global regulatory role of gluconeogenic genes in Escherichia coli revealed by transcriptome network analysis.

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