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Journal of Bacteriology, June 2004, p. 3355-3362, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3355-3362.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

The RNA-Binding Protein Hfq of Listeria monocytogenes: Role in Stress Tolerance and Virulence

Janne K. Christiansen,1 Marianne H. Larsen,2 Hanne Ingmer,2 Lotte Søgaard-Andersen,1 and Birgitte H. Kallipolitis1*

Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M,1 Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University, DK-1870 Frederiksberg C, Denmark2

Received 21 November 2003/ Accepted 11 February 2004

In gram-negative bacteria, the RNA-binding protein Hfq has emerged as an important regulatory factor in a variety of physiological processes, including stress resistance and virulence. In Escherichia coli, Hfq modulates the stability or the translation of mRNAs and interacts with numerous small regulatory RNAs. Here, we studied the role of Hfq in the stress tolerance and virulence of the gram-positive food-borne human pathogen Listeria monocytogenes. We present evidence that Hfq is involved in the ability of L. monocytogenes to tolerate osmotic and ethanol stress and contributes to long-term survival under amino acid-limiting conditions. However, Hfq is not required for resistance to acid and oxidative stress. Transcription of hfq is induced under various stress conditions, including osmotic and ethanol stress and at the entry into the stationary growth phase, thus supporting the view that Hfq is important for the growth and survival of L. monocytogenes in harsh environments. The stress-inducible transcription of hfq depends on the alternative sigma factor {sigma}B, which controls the expression of numerous stress- and virulence-associated genes in L. monocytogenes. Infection studies showed that Hfq contributes to pathogenesis in mice, yet plays no role in the infection of cultured cell lines. This study provides, for the first time, information on the role of Hfq in the stress tolerance and virulence of a gram-positive pathogen.


* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark. Phone: 45 6550 2374. Fax: 45 6550 2467. E-mail: bhk{at}bmb.sdu.dk.


Journal of Bacteriology, June 2004, p. 3355-3362, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3355-3362.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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