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Journal of Bacteriology, June 2009, p. 3919-3927, Vol. 191, No. 12
0021-9193/09/$08.00+0     doi:10.1128/JB.01455-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Virulence Gene Regulation by the agr System in Clostridium perfringens{triangledown}

Kaori Ohtani, Yonghui Yuan, Sufi Hassan, Ruoyu Wang, Yun Wang, and Tohru Shimizu*

Department of Bacteriology, Graduate School of Medical Science, University of Kanazawa, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8203, Japan

Received 16 October 2008/ Accepted 30 March 2009

A gram-positive anaerobic pathogen, Clostridium perfringens, causes clostridial myonecrosis or gas gangrene in humans by producing numerous extracellular toxins and enzymes that act in concert to degrade host tissue. The agr system is known to be important for the regulation of virulence genes in a quorum-sensing manner in Staphylococcus aureus. A homologue for S. aureus agrBD (agrBDSa) was identified in the C. perfringens strain 13 genome, and the role of C. perfringens agrBD (agrBDCp) was examined. The agrBDCp knockout mutant did not express the theta-toxin gene, and transcription of the alpha- and kappa-toxin genes was also significantly decreased in the mutant strain. The mutant strain showed a recovery of toxin production after the addition of the culture supernatant of the wild-type strain, indicating that the agrBDCp mutant lacks a signal molecule in the culture supernatant. An agr-virR double-knockout mutant was constructed to examine the role of the VirR/VirS two-component regulatory system, a key virulence regulator, in agrBDCp-mediated regulation of toxin production. The double-mutant strain could not be stimulated for toxin production with the wild-type culture supernatant. These results indicate that the agrBDCp system plays an important role in virulence regulation and also suggest that VirR/VirS is required for sensing of the extracellular signal and activation of toxin gene transcription in C. perfringens.

* Corresponding author. Mailing address: Department of Bacteriology, Graduate School of Medical Science, Kanazawa University, 1-13, Takara-machi Kanazawa, Ishikawa 3920-8640, Japan. Phone: 81-76-265-2200. Fax: 81-76-234-4230. E-mail: tshimizu{at}med.kanazawa-u.ac.jp

{triangledown} Published ahead of print on 10 April 2009.

Journal of Bacteriology, June 2009, p. 3919-3927, Vol. 191, No. 12
0021-9193/09/$08.00+0     doi:10.1128/JB.01455-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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