title: Role of the Streptococcus gordonii SspB protein in the development of Porphyromonas gingivalis biofilms on streptococcal substrates.
abstract: Porphyromonas gingivalis is an aggressive periodontal pathogen that persists in the mixed-species plaque biofilm on tooth surfaces. P. gingivalis cells attach to the plaque commensal Streptococcus gordonii and this coadhesion event leads to the development of P. gingivalis biofilms. Binding of these organisms is multimodal, involving both the P. gingivalis major fimbrial FimA protein and the species-specific interaction of the minor fimbrial Mfa1 protein with the streptococcal SspB protein. This study examined the contribution of the Mfa1-SspB interaction to P. gingivalis biofilm formation. P. gingivalis biofilms readily formed on substrata of S. gordonii DL1 but not on Streptococcus mutans cells which lack a coadhesion-mediating homologue of SspB. An insertional inactivation of the mfa1 gene in P. gingivalis resulted in a phenotype deficient in S. gordonii binding and unable to form biofilms. Furthermore, analysis using recombinant streptococci and enterococci showed that P. gingivalis biofilms formed on Enterococcus faecalis strains expressing SspB or translational fusions of SspB with SpaP (the non-adherent SspB homologue in S. mutans) containing the P. gingivalis adherence domain (SspB adherence region, BAR) of SspB. In contrast, an isogenic Ssp null mutant of S. gordonii DL1 was unable to support biofilm growth, even though this strain bound to P. gingivalis FimA at levels similar to wild-type S. gordonii DL1. Finally, site-specific mutation of two functional amino acid residues in BAR resulted in SspB polypeptides that did not promote the development of P. gingivalis biofilms. These results suggest that the induction of P. gingivalis biofilms on a streptococcal substrate requires functional SspB-minor fimbriae interactions.
authors.affiliation: Department of Oral Biology, Box 357132, University of Washington, Seattle, WA 98195, USA1.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lamont
authors.affiliation: Department of Oral Biology, Box 357132, University of Washington, Seattle, WA 98195, USA1.
authors.forename: Azza
authors.initials: A
authors.lastname: El-Sabaeny
authors.affiliation: Department of Oral Biology, Box 357132, University of Washington, Seattle, WA 98195, USA1.
authors.forename: Yoonsuk
authors.initials: Y
authors.lastname: Park
authors.affiliation: Bacterin Inc., Bozeman, MT 59717, USA2.
authors.forename: Guy S
authors.initials: GS
authors.lastname: Cook
authors.affiliation: Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA3.
authors.forename: J William
authors.initials: JW
authors.lastname: Costerton
authors.affiliation: Department of Biochemistry, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104, USA4.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Demuth
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D004797:Enzyme-Linked Immunosorbent Assay; D036781:Fimbriae Proteins / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology; D005898:Glass; D008562:Membrane Glycoproteins; D008954:Models, Biological; D009154:Mutation; D010518:Periodontitis / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000502:physiology*; D011485:Protein Binding; D012463:Saliva / Q000378:metabolism / Q000382:microbiology; D013045:Species Specificity; D013291:Streptococcus / Q000235:genetics / Q000378:metabolism*
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; C055764:S-layer proteins; C063055:fimbrillin; C068465:salivary agglutinin receptor, Streptocococcus; D036781:Fimbriae Proteins