The Escherichia con formate:oxygen oxidoreductase supercomplex (FdOx) was investigated with respect to function and composition. Formate oxidoreductase activity was detected in blue native polyacrylamide gel electrophoresis (BN-PAGE) resolved membranes of E. con, which were also capable of cyanide sensitive formate:oxygen oxidoreductase activity. The latter was compromised in strains devoid of specific oxygen reductases, particularly, in those devoid of cytochrome bo(3) or bcI. A principal component analysis (PCA) integrating E. coli aerobic respiratory chain gene transcription, enzyme activity and growth dynamics was performed, correlating formate:oxygen oxidoreductase activity and the transcription of the genes encoding cytochromes bo(3) and bdI, and corroborating previous evidence that associated these complexes in FdOx. (C) 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.