Corynebacterium glutamicum is not only industrially important but also useful as a model organism of pathogenic Gram-positive bacteria, such as C. diphtheria and Mycobacterium tuberculosis. This actinobacterium contains at least two terminal oxidases in the respiratory chain; cytochrome aa3-type cytochrome c oxidase [1] and bd-type menaquinol oxidase [2]. Thus, the chain has two branches of electron flow. The bcc-aa3 branch translocates three protons per electron transferred, while the bd branch translocates only one. Here, we constructed two mutant strains, lacking of either the cytochrome aa3 (ΔctaD) or cytochrome bd oxidase (ΔcydAB), and also plasmids for complementing the deficient genes to investigate their effects on energy conservation and cell growth [3]. The amount of cytochrome bd oxidase was very low even in the ΔctaD mutant, because the expression of the oxidase may be tightly limited with a regulation system. Therefore, we also constructed the mutant overexpressing cytochrome bd to investigate the cytochrome bd branch in more detail. First, we measured H/O ratios of wild-type and mutant cells to evaluate the efficiency of the respiratory chain. 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 ΔctaD mutant. In contrast, the value was 5.23±0.36 for the ΔcydAB mutant. The overexpression of cytochrome bd in the ΔctaD mutant caused further reduction of the value, 2.29±0.29 for the cytochrome bd overexpression mutant. Interestingly, the cells grown in the LB medium showed about 25% higher value compared to that of cells grown in the semi-synthetic medium except for the ΔctaD mutant. Secondly, we investigated the growth rate and cell yield with different nutrients; semi-synthetic medium containing 1% (w/v) glucose and LB medium. The ΔctaD and cytochrome bd overexpression mutants grew less than the wild-type in LB, while they grew about equally insemi-synthetic medium. In contrast, the lack of cytochrome bd oxidase did not largely affect to cell growth in both medium. These findings suggest that correlation between bioenergetics and cell growth is significantly affected by nutritional condition for the growth.