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Corynebacterium glutamicum ^E is involved in responses to cell surface stresses and its activity is controlled by the anti- factor CseE

Jung-Won Youn^2,

¹ Graduate School of Biotechnology, Korea University, Anam-Dong, Sungbuk-Ku, Seoul 136-701, Republic of Korea
² Institute of Biotechnology 1, Heinrich Heine University, Research Center Jülich, D-52425 Jülich, Germany
³ Department of Biotechnology and Bioinformatics, Korea University, Jochiwon, Chungnam 339-700, Republic of Korea
⁴ Department of Oriental Medicine, Semyung University, Checheon, Chungbuk 390-230, Republic of Korea

Correspondence
Heung-Shick Lee
hlee{at}korea.ac.kr

In this study, we demonstrate that ^E, an alternative factor of Corynebacterium glutamicum, is involved in cell surface stresses. Cells in which the sigE gene was deleted evidenced increased sensitivity to magnesium deficiency, as well as to SDS, lysozymes, EDTA and heat. We utilized physiological analyses to show that the downstream gene, designated cseE, encodes an anti- factor. The retarded growth of the cseE mutant cells under ordinary growth conditions could be recovered by an additional deletion of sigE encoding ^E. Under stress conditions, the phenotype of the cseE-overexpressing cells mimicked that of the sigE mutant. The sigE and cseE genes were transcribed into a single transcript, and gene transcription was stimulated by heat. The SigE and CseE proteins interacted physically in vitro, in the form of glutathione S-transferase (GST) and maltose binding protein (MBP) fusion proteins, respectively. 2D-PAGE analysis of the wild-type and mutant crude extracts showed that the sigE mutant failed to synthesize a 34 kDa polypeptide that was normally induced in wild-type cells grown under heat (or SDS)-stressed conditions. The protein turned out to be expressed from ORF NCgl1070 and showed similarity to methyltransferases which may confer resistance to antibiotics. Accordingly, the sigE mutant evidenced extreme sensitivity to antibiotics, including nalidixic acid, penicillin and vancomycin. Finally, we present a discussion of the possible role of the sigE and cseE genes in the acclimation of C. glutamicum to cell surface stress conditions.

Present address: Institute of Molecular Microbiology and Biotechnology, Westphalian Wilhelms University Muenster, Corrensstr. 3, 48149 Muenster, Germany.