title: LuxS-dependent quorum sensing in Porphyromonas gingivalis modulates protease and haemagglutinin activities but is not essential for virulence.
abstract: Porphyromonas gingivalis is a Gram-negative black-pigmented obligate anaerobe implicated in the aetiology of human periodontal disease. The virulence of P. gingivalis is associated with the elaboration of the cysteine proteases Arg-gingipain (Rgp) and Lys-gingipain (Kgp), which are produced at high bacterial cell densities. To determine whether quorum sensing plays a role in the regulation of Rgp and Kgp, biosensors capable of detecting either N-acylhomoserine lactone (AHLs) or the luxS-dependent autoinducer (AI-2) quorum-sensing signalling molecules in spent culture supernatants were first employed. While no AHLs could be detected, the Vibrio harveyi BB170 biosensor was activated by spent P. gingivalis W50 culture supernatants. The P. gingivalis luxS gene was cloned and demonstrated to restore AI-2 production in the Escherichia coli luxS mutant DH5alpha. Mutation of luxS abolished AI-2 production in P. gingivalis. Western blotting using antibodies raised against the recombinant protein revealed that LuxS levels increased throughout growth even though AI-2 activity was only maximally detected at the mid-exponential phase of growth and disappeared by the onset of stationary phase. Similar results were obtained with E. coli DH5alpha transformed with luxS, suggesting that AI-2 production is not limited by a lack of LuxS protein. Analysis of Rgp and Kgp protease activities revealed that the P. gingivalis luxS mutant produced around 45% less Rgp and 30% less Kgp activity than the parent strain. In addition, the luxS mutant exhibited a fourfold reduction in haemagglutinin titre. However, these reductions in virulence determinant levels were insufficient to attenuate the luxS mutant in a murine lesion model of P. gingivalis infection.
authors.affiliation: School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK2.|Institute of Infections and Immunity, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK1.
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Burgess
authors.affiliation: Institute of Infections and Immunity, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK1.
authors.forename: David F
authors.initials: DF
authors.lastname: Kirke
authors.affiliation: School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK2.|Institute of Infections and Immunity, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK1.
authors.forename: Paul
authors.initials: P
authors.lastname: Williams
authors.affiliation: School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK2.
authors.forename: Klaus
authors.initials: K
authors.lastname: Winzer
authors.affiliation: School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK2.|Institute of Infections and Immunity, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK1.
authors.forename: Kim R
authors.initials: KR
authors.lastname: Hardie
authors.affiliation: SmithKline Beecham Pharmaceuticals, Harlow CM19 5AW, UK3.
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Meyers
authors.affiliation: MRC Molecular Pathogenesis Group, Department of Oral Microbiology, St Bartholomews and the Royal London School of Dentistry, 32 Newark St, London E1 2AA, UK4.
authors.forename: Joseph
authors.initials: J
authors.lastname: Aduse-Opoku
authors.affiliation: MRC Molecular Pathogenesis Group, Department of Oral Microbiology, St Bartholomews and the Royal London School of Dentistry, 32 Newark St, London E1 2AA, UK4.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Curtis
authors.affiliation: School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK2.|Institute of Infections and Immunity, Queens Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK1.
authors.forename: Miguel
authors.initials: M
authors.lastname: Cámara
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D016866:Bacteroidaceae Infections / Q000382:microbiology / Q000503:physiopathology; D013437:Carbon-Sulfur Lyases; D010450:Endopeptidases / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006388:Hemagglutinins / Q000378:metabolism*; D006714:Homoserine / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D007783:Lactones / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D016966:Porphyromonas gingivalis / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D015398:Signal Transduction; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D006388:Hemagglutinins; D007783:Lactones; C091088:N-octanoylhomoserine lactone; C088386:homoserine lactone; D006714:Homoserine; D010450:Endopeptidases; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria; D015107:4-Butyrolactone