FIG. 9.

The mhqR mutant shows a higher respiratory chain activity and increased ATP level. (A) Oxygen consumption rates of the wild type and mhqR and qsrR mutants were determined during the exponential growth and stationary phases with glucose or succinate as electron donor using a Clark-type electrode. The results are presented as average values of three biological replicates with standard deviations. (B) To measure oxygen consumption under microaerophilic conditions, discoloration of methylene blue was measured as absorbance change at OD₆₀₀ together with the OD₅₀₀ as bacterial growth. (C) The ATP levels of the wild type and the mhqR mutant were determined during the exponential growth phrase with the ATP Bioluminescence Assay Kit CLS II (Sigma–Aldrich) according to the manufacturer's instructions. The results are from four biological replicates. Error bars represent the standard deviation. ns, p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.001.