title: Distinct roles of long/short fimbriae and gingipains in homotypic biofilm development by Porphyromonas gingivalis.
abstract: BACKGROUND
  Porphyromonas gingivalis, a periodontal pathogen, expresses a number of virulence factors, including long (FimA) and short (Mfa) fimbriae as well as gingipains comprised of arginine-specific (Rgp) and lysine-specific (Kgp) cysteine proteinases. The aim of this study was to examine the roles of these components in homotypic biofilm development by P. gingivalis, as well as in accumulation of exopolysaccharide in biofilms.
  
  
  RESULTS
  Biofilms were formed on saliva-coated glass surfaces in PBS or diluted trypticase soy broth (dTSB). Microscopic observation showed that the wild type strain formed biofilms with a dense basal monolayer and dispersed microcolonies in both PBS and dTSB. A FimA deficient mutant formed patchy and small microcolonies in PBS, but the organisms proliferated and formed a cohesive biofilm with dense exopolysaccharides in dTSB. A Mfa mutant developed tall and large microcolonies in PBS as well as dTSB. A Kgp mutant formed markedly thick biofilms filled with large clumped colonies under both conditions. A RgpA/B double mutant developed channel-like biofilms with fibrillar and tall microcolonies in PBS. When this mutant was studied in dTSB, there was an increase in the number of peaks and the morphology changed to taller and loosely packed biofilms. In addition, deletion of FimA reduced the autoaggregation efficiency, whereas autoaggregation was significantly increased in the Kgp and Mfa mutants, with a clear association with alteration of biofilm structures under the non-proliferation condition. In contrast, this association was not observed in the Rgp-null mutants.
  
  
  CONCLUSIONS
  These results suggested that the FimA fimbriae promote initial biofilm formation but exert a restraining regulation on biofilm maturation, whereas Mfa and Kgp have suppressive and regulatory roles during biofilm development. Rgp controlled microcolony morphology and biovolume. Collectively, these molecules seem to act coordinately to regulate the development of mature P. gingivalis biofilms.
authors.affiliation: Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Suita-Osaka, Japan. kuboniwa@dent.osaka-u.ac.jp
authors.forename: Masae
authors.initials: M
authors.lastname: Kuboniwa
authors.forename: Atsuo
authors.initials: A
authors.lastname: Amano
authors.forename: Ei
authors.initials: E
authors.lastname: Hashino
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Inaba
authors.forename: Nobushiro
authors.initials: N
authors.lastname: Hamada
authors.forename: Koji
authors.initials: K
authors.lastname: Nakayama
authors.forename: Gena D
authors.initials: GD
authors.lastname: Tribble
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lamont
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shizukuishi
mesh_terms: D018829:Adhesins, Bacterial / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D003470:Culture Media; D003546:Cysteine Endopeptidases / Q000502:physiology*; D036781:Fimbriae Proteins / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D000080867:Gingipain Cysteine Endopeptidases; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000502:physiology*
chemical_list: D018829:Adhesins, Bacterial; D003470:Culture Media; D000080867:Gingipain Cysteine Endopeptidases; C063055:fimbrillin; D036781:Fimbriae Proteins; D003546:Cysteine Endopeptidases