title: Characterization of type 2 quorum sensing in Klebsiella pneumoniae and relationship with biofilm formation.
abstract: 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 DH5alpha. 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.
authors.affiliation: Laboratoire de Bactériologie, Faculté de Pharmacie, Université d'Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Balestrino
authors.forename: Janus A J
authors.initials: JA
authors.lastname: Haagensen
authors.forename: Chantal
authors.initials: C
authors.lastname: Rich
authors.forename: Christiane
authors.initials: C
authors.lastname: Forestier
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology; D018441:Biofilms; D013437:Carbon-Sulfur Lyases; D002450:Cell Communication / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria