Transcription of the tricarboxylic acid cycle genes of Corynebacterium glutamicum was investigated. Northern hybridizations revealed that gltA-fkb, odhA-orfA, sucC-sucD, sdhC-sdhA-sdhB-orfB and mdh-orfC were transcribed as polycistronic mRNAs of size 1.9, 4.5, 2.5, 4.0 and 1.7 kb, respectively. The acn-acnR-gat gene cluster was transcribed as a mono-, bi- or tricistronic mRNA, depending on the carbon source. The 2.9-kb (acn) and 1.5-kb (acnR-gat) mRNAs, which were regulated by different promoters upstream of acn and acnR, were inversely expressed in acetate and glucose. The 4.5 kb (acn-acnR-gat) mRNA was constitutively expressed. The sizes of the mRNAs were 2.3, 2.1, 1.5, 1.3, 1.7, 1.5 and 2.9 kb for icd, sucB, fum, mdhB, mqo, aceA and aceB, respectively, indicating monocistronic transcription of these genes. RNA ligase-mediated rapid amplification of cDNA ends analysis of C. glutamicum RNA showed that the transcriptional start sites of gltA, acn, icd, odhA, sucB, sucC, sdhC, fum, mdh, mdhB, mqo, aceA and aceB were located 121, 107, 31, 99, 46, 83, 15, 25, 33, 23, 70, 111 and 183 bp upstream from the first nucleotide of the respective translation initiation codons. Alignment of these gene promoter regions provided evidence for highly conserved sequences that exhibited similarity to the sigma(A) consensus promoter sequences of Gram-positive bacteria. Copyright (c) 2008 S. Karger AG, Basel.