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Journal of Bacteriology, December 2008, p. 8126-8136, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01035-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Loss of RNase R Induces Competence Development in Legionella pneumophila{triangledown} ,{dagger}

Xavier Charpentier,1 Sébastien P. Faucher,1 Sergey Kalachikov,2 and Howard A. Shuman1*

Department of Microbiology, Columbia University Medical Center, 701 West 168th Street, New York, New York 10032,1 Columbia Genome Center, 1150 St Nicholas Avenue, New York, New York 100322

Received 25 July 2008/ Accepted 29 September 2008

RNase R is a processive 3'-5' exoribonuclease with a high degree of conservation in prokaryotes. Although some bacteria possess additional hydrolytic 3'-5' exoribonucleases such as RNase II, RNase R was found to be the only predicted one in the facultative intracellular pathogen Legionella pneumophila. This provided a unique opportunity to study the role of RNase R in the absence of an additional RNase with similar enzymatic activity. We investigated the role of RNase R in the biology of Legionella pneumophila under various conditions and performed gene expression profiling using microarrays. At optimal growth temperature, the loss of RNase R had no major consequence on bacterial growth and had a moderate impact on normal gene regulation. However, at a lower temperature, the loss of RNase R had a significant impact on bacterial growth and resulted in the accumulation of structured RNA degradation products. Concurrently, gene regulation was affected and specifically resulted in an increased expression of the competence regulon. Loss of the exoribonuclease activity of RNase R was sufficient to induce competence development, a genetically programmed process normally triggered as a response to environmental stimuli. The temperature-dependent expression of competence genes in the rnr mutant was found to be independent of previously identified competence regulators in Legionella pneumophila. We suggest that a physiological role of RNase R is to eliminate structured RNA molecules that are stabilized by low temperature, which in turn may affect regulatory networks, compromising adaptation to cold and thus resulting in decreased viability.

* Corresponding author. Mailing address: Department of Microbiology, Columbia University Medical Center, 701 West 168th Street, New York, NY 10032. Phone: (212) 305-6913. Fax: (212) 305-1468. E-mail: has7{at}columbia.edu

{triangledown} Published ahead of print on 10 October 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, December 2008, p. 8126-8136, Vol. 190, No. 24
0021-9193/08/$08.00+0     doi:10.1128/JB.01035-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Hovel-Miner, G., Pampou, S., Faucher, S. P., Clarke, M., Morozova, I., Morozov, P., Russo, J. J., Shuman, H. A., Kalachikov, S. (2009). {sigma}S Controls Multiple Pathways Associated with Intracellular Multiplication of Legionella pneumophila. J. Bacteriol. 191: 2461-2473 [Abstract] [Full Text]  


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