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Abstract

Regulation of aerobic and anaerobic metabolism in E. coli is a well investigated topic and the regulators responsible for the switch between these growth scenarios are known. Several regulatory proteins activate or repress the expression of enzymes depending on the availability of oxygen. These enzymes are either directly involved in respiration or are metabolic enzymes like enzymes of the TCA-cycle. There is a complex interaction between the regulatory and the metabolic network which is until now not completely elucidated. We are aiming to an improved understanding of this interaction by applying a systems biological approach that couples quantitative biological experiments with mathematical modelling. Characterisation of metabolic and regulatory mutants should lead to a deeper understanding of the redox regulation in E. coli. In these mutants enzymes were knocked-out which catalyse for example specific reactions of the TCA-cycle. Mutant strains were characterised in a chemostat under defined conditions to obtain comparable results. Metabolic reactions were examined via measurement of oxygen consumption rates, production of fermentation products, biomass, redox state of the cells and energy charge, as well as the expression rate of specific enzymes via Real-Time PCR. Different oxygen concentrations were adjusted – aerobic, microaerobic and anaerobic conditions – and the reaction of the mutant strains to the changing environment was compared to the reaction of the wild type strain.