The appropriate conditions to switch on the heat shock promoters in Corynebacterium glutamicum were defined by Northern blot analysis. Transcriptional patterns were characterized for the groEL2 gene and the groES-groEL1 and dnaK operons. Transcriptional start points of these genes were determined by primer extension analysis, allowing the identification of CIRCE and HAIR boxes close to the ؊10 and ؊35 regions of the promoters. The presence of both CIRCE and HAIR sequences within a single promoter (P-groEL2) in bacteria is described for the first time. In addition, the dnaK promoter showed ؊10 and ؊35 sequences similar to those recognized by SigH of Mycobacterium and SigR of Streptomyces close to a second transcription start region with ؊10 and ؊35 boxes typical of promoters for housekeeping genes.

Proteome analysis of Corynebacterium glutamicum ATCC 13032 showed that levels of several proteins increased drastically in response to heat shock. These proteins were identified as DnaK, GroEL1, GroEL2, ClpB, GrpE, and PoxB, and their heat response was in agreement with previous transcriptomic results. A major heat-induced protein was absent in the proteome of strain 13032B of C. glutamicum, used for genome sequencing in Germany, compared with the wild-type ATCC 13032 strain. The missing protein was identified as GroEL1 by matrix-assisted laser desorption ionization-time of flight peptide mass fingerprinting, and the mutation was found to be due to an insertion sequence, IsCg1, that was integrated at position 327 downstream of the translation start codon of the groEL1 gene, resulting in a truncated transcript of this gene, as shown by Northern analysis. The GroEL1 chaperone is, therefore, dispensable in C. glutamicum. On the other hand, GroEL2 appears to be essential for growth. Based on these results, the role of the duplicate groEL1 and groEL2 genes is analyzed.Corynebacterium glutamicum (initially named Micrococcus glutamicus) was isolated from a soil sample of the Ueno Zoo in Tokyo as a high producer of glutamic acid (22). The type strain Kyowa Hakko Kogyo strain 534 was reclassified as C. glutamicum (37) and deposited as ATCC 13032.A large number of mutants derived from C. glutamicum ATCC 13032 have been obtained in several laboratories and used for the industrial production of L-glutamic acid, L-lysine, and L-threonine. Due to its industrial relevance, a large research effort for the last two decades has focused on the molecular genetics of this bacterium (4,7,11,23,25,27). The genome of the Kyowa type strain ATCC 13032 was sequenced in Japan (19). In parallel, the genome of a different ATCC 13032 derivative (hereafter named C. glutamicum 13032B) was mapped (4) and sequenced in Germany (20).Heat shock of C. glutamicum cultures increases the secretion of glutamic acid (9) and lysine (30), and it favors the entry of exogenous DNA during transformation by electroporation (38). As in other microorganisms, heat treatment triggers a heat shock response in C. glutamicum (3,29).There is considerable interest in the analysis of the heat shock-induced proteins in C. glutamicum and the heat shock effect on (i) wide-domain regulatory mechanisms and (ii) specific enzymatic steps involved in biosynthesis (24) and secretion (6) of amino acids. The availability of the genome sequence and the improvement of the two-dimensional (2D) protein electrophoresis systems (17, 18, 35) have allowed good progress in the resolution and identification of many proteins of the C. glutamicum proteome. During a collaboration study on the proteome response to heat shock, we observed that a major heat-induced protein was absent in the C. glutamicum 13032B strain available in Bielefeld, Germany, which was present in the ATCC 13032 strain in our laboratory in León, Spain. It was therefore interesting to perform a detailed analysis of the heat ...

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Drs. Barreiro and Martín take sole responsibility for these instances of data duplication and would like to apologize to the readers, reviewers, and editors of both the Journal of Bacteriology and Microbiology.