title: LuxS-based signaling in Streptococcus gordonii: autoinducer 2 controls carbohydrate metabolism and biofilm formation with Porphyromonas gingivalis.
abstract: Communication based on autoinducer 2 (AI-2) is widespread among gram-negative and gram-positive bacteria, and the AI-2 pathway can control the expression of genes involved in a variety of metabolic pathways and pathogenic mechanisms. In the present study, we identified luxS, a gene responsible for the synthesis of AI-2, in Streptococcus gordonii, a major component of the dental plaque biofilm. S. gordonii conditioned medium induced bioluminescence in an AI-2 reporter strain of Vibrio harveyi. An isogenic mutant of S. gordonii, generated by insertional inactivation of the luxS gene, was unaffected in growth and in its ability to form biofilms on polystyrene surfaces. In contrast, the mutant strain failed to induce bioluminescence in V. harveyi and was unable to form a mixed species biofilm with a LuxS-null strain of the periodontal pathogen Porphyromonas gingivalis. Complementation of the luxS mutation in S. gordonii restored normal biofilm formation with the luxS-deficient P. gingivalis. Differential display PCR demonstrated that the inactivation of S. gordonii luxS downregulated the expression of a number of genes, including gtfG, encoding glucosyltransferase; fruA, encoding extracellular exo-beta-D-fructosidase; and lacD encoding tagatose 1,6-diphosphate aldolase. However, S. gordonii cell surface expression of SspA and SspB proteins, previously implicated in mediating adhesion between S. gordonii and P. gingivalis, was unaffected by inactivation of luxS. The results suggest that S. gordonii produces an AI-2-like signaling molecule that regulates aspects of carbohydrate metabolism in the organism. Furthermore, LuxS-dependent intercellular communication is essential for biofilm formation between nongrowing cells of P. gingivalis and S. gordonii.
authors.affiliation: Department of Microbiology, Eastman Dental Institute, University College, London WC1 8LD, United Kingdom. rod.x.mcnab@gsk.com
authors.forename: Roderick
authors.initials: R
authors.lastname: McNab
authors.forename: Suzannah K
authors.initials: SK
authors.lastname: Ford
authors.forename: Azza
authors.initials: A
authors.lastname: El-Sabaeny
authors.forename: Bruno
authors.initials: B
authors.lastname: Barbieri
authors.forename: Guy S
authors.initials: GS
authors.lastname: Cook
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lamont
mesh_terms: D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D050260:Carbohydrate Metabolism; D013437:Carbon-Sulfur Lyases; D015964:Gene Expression Regulation, Bacterial; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D006714:Homoserine / Q000031:analogs & derivatives* / Q000378:metabolism*; D007783:Lactones / Q000378:metabolism*; D016966:Porphyromonas gingivalis / Q000254:growth & development; D015398:Signal Transduction; D013291:Streptococcus / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007783:Lactones; C091088:N-octanoylhomoserine lactone; D006714:Homoserine; D005964:Glucosyltransferases; C101905:GtfG protein, Streptococcus gordonii; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria