Requirement of ArcA for redox regulation in Escherichia coli under microaerobic but not anaerobic or aerobic conditions

Abstract

In Escherichia coli, the two-component regulatory ArcAB system functions as a major control system for the regulation of expression of genes encoding enzymes involved in both aerobic and anaerobic catabolic pathways. Previously, we have described the physiological response of wild-type E. coli to changes in oxygen availability through the complete range from anaerobiosis to full aerobiosis (S. Alexeeva, B. de Kort, G. Sawers, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 182:4934-4940, 2000, and S. Alexeeva, K. J. Hellingwerf, and M. J. Teixeira de Mattos, J. Bacteriol. 184:1402-1406, 2002). Here, we address the question of the contribution of the ArcAB-dependent transcriptional regulation to this response. Wild-type E. coli and a mutant lacking the ArcA regulator were grown in glucose-limited chemostat cultures at controlled levels of oxygen availability ranging from full aerobiosis to complete anaerobiosis. A flux analysis of the distribution of catabolic fluxes over parallel pathways was carried out, and the intracellular redox state (as reflected by the NADH/NAD ratio) was monitored for all steady states. Deletion of ArcA neither significantly altered the in vivo activity of the pyruvate dehydrogenase complex and pyruvate formate lyase nor significantly affected catabolism under fully aerobic and fully anaerobic conditions. In contrast, profound effects of the absence of ArcA were seen under conditions of oxygen-restricted growth: increased respiration, an altered electron flux distribution over the cytochrome o- and d-terminal oxidases, and a significant change in the intracellular redox state were observed. Thus, the ArcA regulator was found to exert major control on flux distribution, and it is concluded that the ArcAB system should be considered a microaerobic redox regulator.

FIG. 1.

Effect of the oxygen supply rate on the yield value for glucose (Y_glc, calculated as grams of dry weight formed per gram of glucose consumed and expressed as a percentage) in the wild-type (open symbols) and ΔarcA (filled symbols) strains.

FIG. 2.

Effect of the oxygen supply rate on the formation rates of acetate (circles) and ethanol (diamonds) of the wild-type (open symbols) and ΔarcA (filled symbols) strains. Data for the wild-type strain are derived from reference .

FIG. 3.

Effect of the oxygen supply rate on the in vivo fluxes via PFL (A) and PDHc (B) of the wild-type (open symbols) and ΔarcA (filled symbols) strains.

FIG. 4.

Effect of the oxygen supply rate on the in vivo TCA cycle activities in the wild-type (open symbols) and ΔarcA (filled symbols) strains. Data for the wild-type strain are derived from reference .

FIG. 5.

(A) Effect of the oxygen supply rate on the total oxygen consumption rates of the wild-type (open symbols) and ΔarcA (filled symbols) strains. (B and C) The calculated electron flux through cytochrome bo oxidase (filled circles and open triangles, respectively), cytochrome bd oxidase (filled diamonds and filled triangles), and rDOT (open squares with dotted line) in the wild-type (B) and ΔarcA (C) strains.

FIG. 6.

Effect of the oxygen supply rate on the NADH/NAD ratio in the wild-type (open symbols) and ΔarcA (filled symbols) strains. Data for the wild-type strain are derived from reference .