FIG 4.

Functional heterologous expression of CIO in E. coli MB43, which lacks type 1 NADH dehydrogenase and three quinol oxidases. MB43 was transformed with pUC-cioAB or pUC-cydAB, and the transformants were cultivated in 100 ml LB medium in 300-ml square bottles. The medium was bubbled with air at a gas flux rate of 500 ml/min for aerobic conditions or with a gas mixture consisting of 2% O₂ and 98% N₂ at a gas flux rate of 150 ml/min for microaerobic conditions. The data shown are representatives from two independent experiments. The doubling times ± standard deviations are indicated in brackets. The same plots in linear scale are shown in Fig. S6 in the supplemental material.