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Transcriptional profiling of Corynebacterium glutamicum metabolism during organic acid production under oxygen deprivation conditions

Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizugawa, Kyoto, 619-0292, Japan

Correspondence
Hideaki Yukawa
mmg-lab{at}rite.or.jp

A transcriptional profiling of the metabolism of Corynebacterium glutamicum under oxygen deprivation conditions is reported. It was observed that the glucose consumption rate per cell when C. glutamicum cells were incubated under oxygen deprivation conditions was higher than that achieved by cells incubated under aerobic growth conditions. Furthermore, DNA microarray and quantitative RT-PCR analyses revealed that the genes of several key enzymes of the glycolytic and organic acid production pathways, including gapA, pgk, tpi, ppc, ldhA and mdh, were significantly upregulated under oxygen deprivation conditions. The corresponding enzymic activities consistently correlated with the regulation patterns of the genetic expression observed at the transcriptional level. Studies of lacZ fusions with the gapA, ldhA and mdh genes indicated not only that these genes are strongly induced at the onset of the stationary phase under aerobic growth conditions, but also that high expression levels are maintained under oxygen deprivation conditions. These results indicate that the genetic expression of several key metabolic enzymes in C. glutamicum cells incubated under oxygen deprivation conditions is chiefly regulated at the transcriptional level. The physiological consequence of the observed increased transcription under oxygen deprivation conditions is an increased rate of carbon source consumption, which is accompanied by a concomitant increase in organic acid production.

The GenBank/EMBL/DDBJ accession nos for the complete C. glutamicum R genome DNA and native episome sequences are AP009044 and AP009045, respectively.

The array data discussed in this publication have been deposited in GenomeNet EXPRESSION (http://www.genome.jp/kegg/expression/) and are accessible through accession number ex0001754.

Tables showing oligonucleotides used in this study, expression data of genes observed to be up- or down-regulated under oxygen deprivation conditions, and the COGs functional annotation of genes and the numbers of genes showing increased or decreased transcriptional levels during oxygen deprived reactions, are available as supplementary data with the online version of this paper.

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