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Journal of Bacteriology, December 2008, p. 7719-7727, Vol. 190, No. 23
0021-9193/08/$08.00+0     doi:10.1128/JB.01573-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Characterization of Genes Regulated Directly by the VirR/VirS System in Clostridium perfringens{triangledown}

Kayo Okumura,1,{dagger} Kaori Ohtani,2 Hideo Hayashi,1 and Tohru Shimizu2*

Department of Infection Biology, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575,1 Department of Bacteriology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa 920-8640, Japan2

Received 29 September 2007/ Accepted 1 September 2008

Analysis of the complete sequence of the genome of Clostridium perfringens strain 13 resulted in identification of five genes, including pfoA (encoding theta toxin) and vrr (encoding VirR/VirS-regulated RNA), with consensus VirR-binding sequences upstream of the open reading frame (ORF), suggesting that expression of these genes may be regulated directly by the two-component VirR/VirS system. To test this possibility, we examined VirR/VirS system-mediated transcriptional regulation of three genes, virT, ccp (encoding alpha-clostripain), and virU, with the novel VirR-binding sequences. Northern analysis revealed that the steady-state levels (increases or decreases in the amounts of RNA expressed) of virT, ccp, and virU mRNAs were lower in a virR mutant strain than in the wild-type strain, as were the levels of the pfoA and vrr transcripts. The consensus VirR-binding sites were located similarly relative to the transcription start sites in the virT, ccp, and virU promoters. Mutation and overexpression analyses with virT and virU revealed that the virT gene product has a negative effect on expression of pfoA and ccp, whereas the virU gene product positively affects expression of pfoA, virT, ccp, and vrr. Nonsense and frameshift mutations in the virT or virU putative ORF did not affect the regulatory functions, suggesting that virT and virU may encode RNA regulators rather than proteins. These results suggest that a complex regulatory network, perhaps involving several regulatory RNA molecules, governs the expression of the VirR/VirS regulon in C. perfringens.

* Corresponding author. Mailing address: Department of Bacteriology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-Machi, Kanazawa, Ishikawa 920-8640, Japan. Phone: 81-76-265-2201. Fax: 81-76-234-4230. E-mail: tshimizu{at}med.kanazawa-u.ac.jp

{triangledown} Published ahead of print on 12 September 2008.

{dagger} Present address: Department of Infectious Diseases, Research Institute, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan.

Journal of Bacteriology, December 2008, p. 7719-7727, Vol. 190, No. 23
0021-9193/08/$08.00+0     doi:10.1128/JB.01573-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Ohtani, K., Yuan, Y., Hassan, S., Wang, R., Wang, Y., Shimizu, T. (2009). Virulence Gene Regulation by the agr System in Clostridium perfringens. J. Bacteriol. 191: 3919-3927 [Abstract] [Full Text]  


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