Identification of a gene encoding a transporter essential for utilization of C4 dicarboxylates in Corynebacterium glutamicum.
Appl. Environ. Microbiol. 74: 5290-5296. 2008.
H. Teramoto, T. Shirai, M. Inui and H. Yukawa.

The Corynebacterium glutamicum R genome contains a total of eight genes encoding proteins with sequence similarity to C4-dicarboxylate transporters identified in other bacteria. Three of the genes encode proteins within the dicarboxylate/amino acid:cation symporter (DAACS) family, another three encode proteins within the tripartite ATP-independent periplasmic transporter (TRAP-T) family, and two encode proteins within the divalent anion/Na(+) symporter (DASS) family. We observed that a mutant strain deficient in one of these genes, destignated dcsT, of the DASS family did not aerobically grow on the C4-dicarboxylates, succinate, fumarate, and malate as the sole carbon sources. A mutant strain deficient in each of the other seven genes grew as well as the wild type strain under the same conditions, although one of these genes is a homologue to dctA of the DAACS family involved in aerobic growth on C4-dicarboxylates in various bacteria. The utilization of C4-dicarboxylates was markedly enhanced by overexpression of the dcsT gene. We confirmed that the uptake of (13)C-labeled succinate observed for the wild type cells was hardly detected in the dcsT-deficient mutant, but was markedly enhanced in a dcsT-overexpressed strain. These results suggested that in C. glutamicum, the uptake of C4-dicarboxylates for aerobic growth was mainly mediated by the DASS transporter encoded by dcsT. The expression level of dcsT gene transiently increased in the early exponential phase during growth on nutrient-rich medium. The expression was enhanced by addition of succinate in the mid exponential phase, and was repressed by addition of glucose in the early exponential phase.