The aerobic respiratory chain of Escherichia coli: from genes to supercomplexes

In spite of the large number of reports on the aerobic respiratory chain of Escherichia coli, from gene transcription regulation to enzyme kinetics and structural studies, an integrative perspective of this pathway is yet to be produced. Here, a multi-level analysis of the aerobic respiratory chain of E. coli was performed to find correlations between gene transcription, enzyme activity, growth dynamics, and supercomplex formation and composition. The transcription level of all genes encoding the aerobic respiratory chain of E. coli varied significantly in response to bacterial growth. Coordinated expression patterns were observed between the genes encoding NADH : quinone oxidoreductase and complex I (NDH-1), alternative NADH : quinone oxidoreductase (NDH-2) and cytochrome bdI, and also between sdhA and appC, encoding succinate dehydrogenase and cytochrome bdII, respectively. In general, the rates of the respiratory chain activities increased from mid-exponential to late-stationary phase, with no significant further variation occurring until the mid-stationary phase. Multi-level correlations between gene transcription, enzyme activity and growth dynamics were also found in this study. The previously reported NADH dehydrogenase and formate : oxygen oxidoreductase supercomplexes of E. coli were already assembled at mid-exponential phase and remained throughout growth. A new succinate oxidase supercomplex composed of succinate dehydrogenase and cytochrome bdII was identified, in agreement with the suggestion provided by the coordinated transcription of sdhA and appC.