title: Quorum sensing affects biofilm formation through lipopolysaccharide synthesis in Klebsiella pneumoniae.
abstract: Biofilm formation by Klebsiella pneumoniae is modulated by quorum sensing through the synthesis of interspecies AI-2 autoinducers. We characterized in K. pneumoniae the genes homologous to those described in Escherichia coli involved in AI-2 transport, and created two isogenic mutants deleted of lsrCD and tqsA. The levels of extracellular AI-2 with lsrCD and tqsA knockout mutants showed increased and lowered concentrations of AI-2, respectively. The level of transcripts of luxS, the gene responsible for AI-2 synthesis, was increased in sessile cells of the tqsA mutant. In contrast, the expression of the AI-2 import regulator genes lsrR and lsrK was decreased. In addition, the two mutants lsrCD and tqsA formed biofilms with greater biomass but impaired architecture. Since exopolysaccharides play a main role in K. pneumoniae biofilm formation, we investigated their relationship with AI-2 synthesis. None of the mutations in luxS and the AI-2 transport systems affected the expression of three capsule polysaccharide-related genes (wzi, wza and wzx), but all induced an increase in the expression of two lipopolysaccharide (LPS)-synthesis-related genes, wbbM and wzm. AI-2 therefore seems to act as a regulator of biofilm formation and LPS synthesis in sessile K. pneumoniae cells.
authors.affiliation: Laboratoire de Bactériologie, UFR Pharmacie, Université d'Auvergne Clermont1, UFR Pharmacie Bactériologie, 28 place Henri Dunant 63000 Clermont-Ferrand, France.
authors.forename: Cécilia
authors.initials: C
authors.lastname: De Araujo
authors.forename: Damien
authors.initials: D
authors.lastname: Balestrino
authors.forename: Lucile
authors.initials: L
authors.lastname: Roth
authors.forename: Nicolas
authors.initials: N
authors.lastname: Charbonnel
authors.forename: Christiane
authors.initials: C
authors.lastname: Forestier
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D001692:Biological Transport / Q000235:genetics; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D005798:Genes, Bacterial; D006714:Homoserine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007783:Lactones / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000096:biosynthesis; D009154:Mutation; D016133:Polymerase Chain Reaction; D053038:Quorum Sensing; D017384:Sequence Deletion; D015398:Signal Transduction / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D007783:Lactones; D008070:Lipopolysaccharides; C091088:N-octanoylhomoserine lactone; D006714:Homoserine