Correlation between proton translocation and growth: genetic analysis of the respiratory chain of Corynebacterium...

Corynebacterium glutamicum contains at least two terminal oxidases in the respiratory chain; cytochrome aa(3)-type cytochrome c oxidase and bd-type menaquinol oxidase. Thus, the chain has two branches of electron flow. The bcc-aa(3) branch translocates three protons per electron transferred, while the bd branch translocates only one. In this study, we constructed two mutant strains, lacking of either subunit I of the cytochrome c oxidase (DeltactaD) or subunits I and II of the quinol oxidase (DeltacydAB), and also plasmids to complement the deficient genes to investigate their effects on energy conservation and cell growth. We measured H(+)/O ratios of C. glutamicum wild-type and mutant cells grown aerobically. The H(+)/O ratio of the wild-type cells grown in the semi-synthetic medium was 3.94 +/- 0.30, while the value was 2.76 +/- 0.25 for the DeltactaD mutant. In contrast, the value was 5.23 +/- 0.36 for the DeltacydAB mutant. The cells grown in the LB medium showed higher value compared to that of cells grown in the semi-synthetic medium. The DeltactaD mutant grew less than the wild-type in LB medium, while they grew about equally in semi-synthetic medium. Correlation between bioenergetics and growth of C. glutamicum was significantly affected by the growth nutrients.