Monday, August 11, 2008
P114

Transcriptional regulation of the narKGHJI operon involved in nitrate respiration system in Corynebacterium glutamicum

Taku Nishimura1, Haruhiko Teramoto2, Alain A. Vertès1, Masayuki Inui1, and Hideaki Yukawa1. (1) Microbiology Research Group, Research Institute of Innovative Technology for the Earth, 9-2, Kizugawadai, Kizugawa, Kyoto, Japan, (2) Molecular Microbiology and Biotechnology Group, Research Institute of Innovative Technology for the Earth, 9-2, Kizugawadai, Kizugawa, Kyoto, Japan

 Corynebacterium glutamicum, a high-GC gram-positive soil bacterium, has been widely used for industrial production of various amino acids and nucleic acids. Our recent study showed that this bacterium grows anaerobically using nitrate as a terminal electron acceptor. This property is attributed to the presence of a narKGHJI operon, which comprises putative nitrate/nitrite transporter (narK) and nitrate reductase complex (narGHJI) genes. We also observed that the expression of the operon is induced by anaerobiosis and additionally by the presence of nitrate. In this study, we identified a novel gene, arnR, which encodes a transcriptional regulator that represses the expression of the narKGHJI operon in C. glutamicum cells under aerobic conditions. This activity contrasts with that of Fnr, which anaerobically activates the transcription of nitrate reductase genes in Escherichia coli and Bacillus subtilis. To our knowledge, the aerobic repression of the nitrate reductase operon has not yet been observed in any other bacterial nitrate respiration system. ArnR was also shown to directly repress the expression of the hmp gene, encoding flavohemoglobin, and to positively regulate its own gene product.

 This work was partially supported by a grant from the New Energy and Industrial Technology Development Organization (NEDO). 


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