Role of Cytochrome <i>bd</i> Oxidase from <i>Corynebacterium glutamicum</i> in Growth and Lysine Production

Abstract

ABSTRACT 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 ∼45% and of the maximal biomass by ∼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 ∼12%. Thus, the respiratory chain was shown to be a target for improving amino acid production by C. glutamicum .