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Applied and Environmental Microbiology, November 2008, p. 7002-7015, Vol. 74, No. 22
0099-2240/08/$08.00+0 doi:10.1128/AEM.01327-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
Global Transcription and Metabolic Flux Analysis of Escherichia coli in Glucose-Limited Fed-Batch Cultivations
,
K. Lemuth,1,
,
T. Hardiman,2,
S. Winter,3
D. Pfeiffer,2
M. A. Keller,2,¶
S. Lange,1,||
M. Reuss,2
R. D. Schmid,1 and
M. Siemann-Herzberg2*
Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany,1 Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany,2 Institute of Stochastics and Applications, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany3
Received 13 June 2008/ Accepted 11 September 2008
A time series of whole-genome transcription profiling of Escherichia coli K-12 W3110 was performed during a carbon-limited fed-batch process. The application of a constant feed rate led to the identification of a dynamic sequence of diverse carbon limitation responses (e.g., the hunger response) and at the same time provided a global view of how cellular and extracellular resources are used: the synthesis of high-affinity transporters guarantees maximal glucose influx, thereby preserving the phosphoenolpyruvate pool, and energy-dependent chemotaxis is reduced in order to provide a more economic "work mode." 
S-mediated stress and starvation responses were both found to be of only minor relevance. Thus, the experimental setup provided access to the hunger response and enabled the differentiation of the hunger response from the general starvation response. Our previous topological model of the global regulation of the E. coli central carbon metabolism through the crp, cra, and relA/spoT modulons is supported by correlating transcript levels and metabolic fluxes and can now be extended. The substrate is extensively oxidized in the tricarboxylic acid (TCA) cycle to enhance energy generation. However, the general rate of oxidative decarboxylation within the pentose phosphate pathway and the TCA cycle is restricted to a minimum. Fine regulation of the carbon flux through these pathways supplies sufficient precursors for biosyntheses. The pools of at least three precursors are probably regulated through activation of the (phosphoenolpyruvate-)glyoxylate shunt. The present work shows that detailed understanding of the genetic regulation of bacterial metabolism provides useful insights for manipulating the carbon flux in technical production processes.
* Corresponding author. Mailing address: Allmandring 31, 70569 Stuttgart, Germany. Phone: 49 711 685-65161. Fax: 49 711 685-65164. E-mail: siemann{at}ibvt.uni-stuttgart.de
Published ahead of print on 19 September 2008.
Supplemental material for this article may be found at http://aem.asm.org/.
These authors contributed equally to this paper.
Present address: Institute of Biochemical Engineering, Allmandring 31, 70569 Stuttgart, Germany.
¶ Present address: Fraunhofer Institute for Manufacturing Engineering and Automation, Department of Cleanroom Manufacturing, Nobelstrasse 12, 70569 Stuttgart, Germany.
|| Present address: Roche Diagnostics AG, Forrenstrasse (B. 6, R. 03.071-09), CH-6343 Rotkreuz, Switzerland.
Applied and Environmental Microbiology, November 2008, p. 7002-7015, Vol. 74, No. 22
0099-2240/08/$08.00+0 doi:10.1128/AEM.01327-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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