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Journal of Bacteriology, April 2005, p. 2870-2880, Vol. 187, No. 8
0021-9193/05/$08.00+0     doi:10.1128/JB.187.8.2870-2880.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Characterization of Type 2 Quorum Sensing in Klebsiella pneumoniae and Relationship with Biofilm Formation

Damien Balestrino,1 Janus A. J. Haagensen,2 Chantal Rich,3 and Christiane Forestier1*

Laboratoire de Bactériologie, Faculté de Pharmacie, Université d'Auvergne,1 CHU, Clermont-Ferrand, France,3 Center of Biomedical Microbiology, BioCentrum-DTU, Technical University of Denmark, Lyngby, Denmark2

Received 15 November 2004/ Accepted 11 January 2005

Quorum sensing is a process by which bacteria communicate by using secreted chemical signaling molecules called autoinducers. Many bacterial species modulate the expression of a wide variety of physiological functions in response to changes in population density by this mechanism. In this study, the opportunistic pathogen Klebsiella pneumoniae was observed to secrete type 2 signaling molecules. A homologue of luxS, the gene required for AI-2 synthesis in Vibrio harveyi, was isolated from the K. pneumoniae genome. A V. harveyi bioassay showed the luxS functionality in K. pneumoniae and its ability to complement the luxS-negative phenotype of Escherichia coli DH5{alpha}. Autoinducer activity was detected in the supernatant, and maximum expression of specific messengers detected by quantitative reverse transcription-PCR analysis occurred during the late exponential phase. The highest levels of AI-2 were observed in minimal medium supplemented with glycerol. To determine the potential role of luxS in colonization processes, a K. pneumoniae luxS isogenic mutant was constructed and tested for its capacity to form biofilms in vitro on an abiotic surface and to colonize the intestinal tract in a murine model. No difference was observed in the level of intestinal colonization between the wild-type strain and the luxS mutant. Microscopic analysis of biofilm structures revealed that the luxS mutant was able to form a mature biofilm but with reduced capacities in the development of microcolonies, mostly in the early steps of biofilm formation. These data suggest that a LuxS-dependent signal plays a role in the early stages of biofilm formation by K. pneumoniae.

* Corresponding author. Mailing address: Laboratoire de Bactériologie, Université d'Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France. Phone: 33 4 73 17 79 94. Fax: 33 4 73 17 83 70. E-mail: christiane.forestier{at}u-clermont1.fr.

Journal of Bacteriology, April 2005, p. 2870-2880, Vol. 187, No. 8
0021-9193/05/$08.00+0     doi:10.1128/JB.187.8.2870-2880.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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