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Journal of Bacteriology, October 2009, p. 6340-6344, Vol. 191, No. 20
0021-9193/09/$08.00+0     doi:10.1128/JB.00756-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Characterization of a Mycobacterium tuberculosis ESX-3 Conditional Mutant: Essentiality and Rescue by Iron and Zinc {triangledown}

Agnese Serafini, Francesca Boldrin, Giorgio Palù, and Riccardo Manganelli*

Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, Padua, Italy

Received 11 June 2009/ Accepted 7 August 2009

Recently, a novel type of secretory pathway, type VII secretion systems (T7SSs), has been characterized in mycobacteria. The chromosomes of Mycobacterium tuberculosis and Mycobacterium bovis encode five T7SSs (ESX-1 to ESX-5). The best characterized of them, ESX-1, is involved in host-pathogen interactions, and its deletion is one of the main causes of M. bovis BCG attenuation. Another T7SS, ESX-3, has been previously shown to be transcriptionally controlled by the zinc uptake repressor (Zur) and by the iron-dependent transcriptional repressor (IdeR), suggesting that it might be involved in zinc and iron homeostasis. In this study, we characterized an M. tuberculosis conditional mutant in which transcription of the ESX-3 gene cluster can be downregulated by anhydrotetracycline. We showed that this T7SS is essential for growth and that this phenotype can be complemented by zinc, iron, or supernatant from a wild-type parental strain culture, demonstrating that the ESX-3 secretion system is responsible for the secretion of some soluble factor(s) required for growth that is probably involved in optimal iron and zinc uptake.

* Corresponding author. Mailing address: Department of Histology, Microbiology, and Medical Biotechnologies, University of Padua, Via Gabelli 63, 35121 Padua, Italy. Phone: 39 49 827 2366. Fax: 39 49 827 2355. E-mail: riccardo.manganelli{at}unipd.it

{triangledown} Published ahead of print on 14 August 2009.

Journal of Bacteriology, October 2009, p. 6340-6344, Vol. 191, No. 20
0021-9193/09/$08.00+0     doi:10.1128/JB.00756-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Siegrist, M. S., Unnikrishnan, M., McConnell, M. J., Borowsky, M., Cheng, T.-Y., Siddiqi, N., Fortune, S. M., Moody, D. B., Rubin, E. J. (2009). Mycobacterial Esx-3 is required for mycobactin-mediated iron acquisition. Proc. Natl. Acad. Sci. USA 106: 18792-18797 [Abstract] [Full Text]  


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