Publications

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3 Publications visible to you, out of a total of 3
Towards a Systems Level Understanding of the Oxygen Response of Escherichia coli

Abstract (Expand)

Escherichia coli is a facultatively anaerobic bacterium. With glucose if no external electron acceptors are available, ATP is produced by substrate level phosphorylation. The intracellular redox balance … is maintained by mixed-acid fermentation, that is, the production and excretion of several organic acids. When oxygen is available, E. coli switches to aerobic respiration to achieve redox balance and optimal energy conservation by proton translocation linked to electron transfer. The switch between fermentative and aerobic respiratory growth is driven by extensive changes in gene expression and protein synthesis, resulting in global changes in metabolic fluxes and metabolite concentrations. This oxygen response is determined by the interaction of global and local genetic regulatory mechanisms, as well as by enzymatic regulation. The response is affected by basic physical constraints such as diffusion, thermodynamics and the requirement for a balance of carbon, electrons and energy (predominantly the proton motive force and the ATP pool). A comprehensive systems level understanding of the oxygen response of E. coli requires the integrated interpretation of experimental data that are pertinent to the multiple levels of organization that mediate the response. In the pan-European venture, Systems Biology of Microorganisms (SysMO) and specifically within the project Systems Understanding of Microbial Oxygen Metabolism (SUMO), regulator activities, gene expression, metabolite levels and metabolic flux datasets were obtained using a standardized and reproducible chemostat-based experimental system. These different types and qualities of data were integrated using mathematical models. The approach described here has revealed a much more detailed picture of the aerobic-anaerobic response, especially for the environmentally critical microaerobic range that is located between unlimited oxygen availability and anaerobiosis.

Authors: , , , , , , S. Kunz, , , , , ,

Date Published: 7th May 2014

Publication Type: Not specified

Glucose Transport in Escherichia coli Mutant Strains with Defects in Sugar Transport Systems

Abstract (Expand)

In Escherichia coli several systems are known to transport glucose into the cytoplasm. The main glucose uptake system under batch conditions is the glucose phosphoenolpyruvate:carbohydrate phosphotransferase … system (glucose-PTS), but also the mannose-PTS, as well as the galactose and maltose transporters can translocate glucose. Mutant strains which lack the EIIBC protein of the glucose-PTS have been previously investigated because their lower rate of acetate formation offers advantages in industrial applications. Nevertheless, a systematic study to analyze the impact of the different glucose uptake systems has not been undertaken. Specifically, how the bacteria cope with the deletion of the major glucose uptake system and which alternative transporters react to compensate for this deficit has not been studied in detail. Therefore, a series of mutant strains were analyzed in aerobic and anaerobic batch cultures, as well as in glucose limited continuous cultivations. Deletion of EIIBC, disturbs glucose transport severely. cAMP-CRP levels rise, induction of the mgl-operon occurs. Nevertheless mgl transcription is not essential, as deletion of this transporter did not affect growth rate; the activities of the remaining transporters seems to be sufficient by induction of the galactose and maltose transporters. Despite the strong up-regulation of mgl under glucose limitations, deletion of this transport-system did not lead to further changes.

Editor:

Date Published: 8th Oct 2012

Publication Type: Not specified

Characterization of E. coli MG1655 and frdA and sdhC mutants at various aerobiosis levels

Abstract

Not specified

Authors: , S. Frixel, ,

Date Published: 1st Jun 2011

Publication Type: Not specified

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