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Authors: Wulffen, Joachim von
Sawodny, Oliver
Feuer, Ronny
Title: Transition of an anaerobic Escherichia coli culture to aerobiosis: balancing mRNA and protein levels in a demand-directed dynamic flux balance analysis
Issue Date: 2016 Zeitschriftenartikel 17 PLOS ONE 11 (2016), Nr. 7, e0158711
ISSN: 1932-6203
Abstract: The facultative anaerobic bacterium Escherichia coli is frequently forced to adapt to changing environmental conditions. One important determinant for metabolism is the availability of oxygen allowing a more efficient metabolism. Especially in large scale bioreactors, the distribution of oxygen is inhomogeneous and individual cells encounter frequent changes. This might contribute to observed yield losses during process upscaling. Short-term gene expression data exist of an anaerobic E. coli batch culture shifting to aerobic conditions. The data reveal temporary upregulation of genes that are less efficient in terms of energy conservation than the genes predicted by conventional flux balance analyses. In this study, we provide evidence for a positive correlation between metabolic fluxes and gene expression. We then hypothesize that the more efficient enzymes are limited by their low expression, restricting flux through their reactions. We define a demand that triggers expression of the demanded enzymes that we explicitly include in our model. With these features we propose a method, demand-directed dynamic flux balance analysis, dddFBA, bringing together elements of several previously published methods. The introduction of additional flux constraints proportional to gene expression provoke a temporary demand for less efficient enzymes, which is in agreement with the transient upregulation of these genes observed in the data. In the proposed approach, the applied objective function of growth rate maximization together with the introduced constraints triggers expression of metabolically less efficient genes. This finding is one possible explanation for the yield losses observed in large scale bacterial cultivations where steady oxygen supply cannot be warranted.
Appears in Collections:07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik

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von Wulffen, Sawodny, Feuer - 2016 - Transition of an Anaerobic Escherichia coli Culture to Aerobiosis Balancing mRNA and Protein Levels.PDFResearch article1,81 MBAdobe PDFView/Open
journal.pone.0158711.s001.PDFSupporting information 179,41 kBAdobe PDFView/Open
journal.pone.0158711.s002.PDFSupporting information 273,88 kBAdobe PDFView/Open

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