Role of cytochrome bd oxidase from Corynebacterium glutamicum in growth and lysine production

Corynebacterium glutamicum possesses two terminal oxidases, cytochrome aa(3) and cytochrome bd. Cytochrome aa(3) forms a supercomplex with the cytochrome bc(1) complex, which contains an unusual diheme cytochrome c(1). Both the bc(1)-aa(3) supercomplex and cytochrome bd transfer reducing equivalents from menaquinol to oxygen; however, they differ in their proton translocation efficiency by a factor of three. Here, we analyzed the role of cytochrome bd for growth and lysine production. When cultivated in glucose minimal medium, a cydAB deletion mutant of C glutamicum ATCC 13032 grew like the wild type in the exponential phase, but growth thereafter was inhibited, leading to a biomass formation 40% less than that of the wild type. Constitutive overproduction of functional cytochrome bd oxidase in ATCC 13032 led to a reduction of the growth rate by similar to 45% and of the maximal biomass by similar to 35%, presumably as a consequence of increased electron flow through the inefficient cytochrome bd oxidase. In the L-lysine-producing C. glutamicum strain MH20-22B, deletion of the cydAB genes had only minor effects on growth rate and biomass formation, but lysine production was increased by similar to 12%. Thus, the respiratory chain was shown to be a target for improving amino acid production by C. glutamicum.