The influence of acetate in the medium to the global gene expression of C. glutamicum wild type (WT) and the C. glutamicum ΔcyaB mutant (ΔcyaB)

The cAMP-dependent transcriptional regulator GlxR serves as a central hub in the regulatory network of the actinobacterial model organism Corynebacterium glutamicum and controls expression of ~10% of all genes. The consequences of a lowered cAMP level are mostly unkown. A single gene (cyaB) for a cAMP-synthesizing adenylate cyclase was identified and it had been reported that a cyaB mutant grows like the wild type on glucose, but has a strong growth defect in the presence of acetate. Our work aimed to understand the molecular basis for the acetate sensitivity of a ΔcyaB mutant and improve our knowledge on the physiological function of cAMP. Our results indicate that a diminished expression of the GlxR-activated genes for the cytochrome bc1-aa3 supercomplex in the ΔcyaB mutant causes a reduced capacity to build up membrane potential. This deficiency becomes evident in the presence of acetate or the protonophore CCCP, which increase the proton permeability of the cytoplasmic membrane, and has systemic effects on transport processes including oxidative phosphorylation. The acetate sensitivity of the ΔcyaB mutant could be abolished by a single amino acid exchange in GlxR. Our results demonstrate a key role of cAMP and GlxR in the control of energy metabolism in corynebacteria. DNA microarray analyses of the ΔcyaB mutant and the wild type (WT), grown in minimal medium with glucose and acetate (100 mM each) were performed. For this purpose RNA was isolated from exponentially growing cells cultivated in CGXII medium containing glucose and acetate (each 100 mM) as carbon source. Three biological replicates of both strains were performed.