Identification and Characterization of the Dicarboxylate Uptake System DccT inCorynebacterium glutamicum

Many bacteria can utilize C4 -carboxylates as carbon and energy sources. However,Corynebacterium glutamicum ATCC 13032 is not able to use tricarboxylic acid cycle intermediates such as succinate, fumarate, andl -malate as sole carbon sources. Upon prolonged incubation, spontaneous mutants which had gained the ability to grow on succinate, fumarate, andl -malate could be isolated. DNA microarray analysis showed higher mRNA levels of cg0277, which subsequently was nameddccT , in the mutants than in the wild type, and transcriptional fusion analysis revealed that a point mutation in the promoter region ofdccT was responsible for increased expression. The overexpression ofdccT was sufficient to enable theC. glutamicum wild type to grow on succinate, fumarate, andl -malate as the sole carbon sources. Biochemical analyses revealed that DccT, which is a member of the divalent anion/Na+ symporter family, catalyzes the effective uptake of dicarboxylates like succinate, fumarate,l -malate, and likely also oxaloacetate in a sodium-dependent manner.