Identification and characterization of the dicarboxylate uptake system DccT in Corynebacterium glutamicum

Many bacteria can utilize [C.sub.4]-carboxylates as carbon and energy sources. However, Corynebacterium glutamicum ATCC 13032 is not able to use tricarboxylic acid cycle intermediates such as succinate, fumarate, and L-malate as sole carbon sources. Upon prolonged incubation, spontaneous mutants which had gained the ability to grow on succinate, fumarate, and L-malate could be isolated. DNA microarray analysis showed higher mRNA levels of cg0277, which subsequently was named dccT, in the mutants than in the wild type, and transcriptional fusion analysis revealed that a point mutation in the promoter region of dccT was responsible for increased expression. The overexpression of dccT was sufficient to enable the C. glutamicum wild type to grow on succinate, fumarate, and L-malate as the sole carbon sources. Biochemical analyses revealed that DccT, which is a member of the divalent anion/[Na.sup.+] symporter family, catalyzes the effective uptake of dicarboxylates like succinate, fumarate, L-malate, and likely also oxaloacetate in a sodium-dependent manner.