title: Role of extracytoplasmic function sigma factors in biofilm formation of Porphyromonas gingivalis.
abstract: BACKGROUND
  Porphyromonas gingivalis has been implicated as a major pathogen in the development and progression of chronic periodontitis. P. gingivalis biofilm formation in the subgingival crevice plays an important role in the ability of the bacteria to tolerate stress signals outside the cytoplasmic membrane. Some bacteria use a distinct subfamily of sigma factors to regulate their extracytoplasmic functions (the ECF subfamily). The objective of this study was to determine if P. gingivalis ECF sigma factors affect P. gingivalis biofilm formation.
  
  
  METHODS
  To elucidate the role of ECF sigma factors in P. gingivalis, chromosomal mutants carrying a disruption of each ECF sigma factor-encoding gene were constructed. Bacterial growth curves were measured by determining the turbidity of bacterial cultures. The quantity of biofilm growing on plates was evaluated by crystal violet staining.
  
  
  RESULTS
  Comparison of the growth curves of wild-type P. gingivalis strain 33277 and the ECF mutants indicated that the growth rate of the mutants was slightly lower than that of the wild-type strain. The PGN_0274- and PGN_1740-defective mutants had increased biofilm formation compared with the wild-type (p < 0.001); however, the other ECF sigma factor mutants or the complemented strains did not enhance biofilm formation.
  
  
  CONCLUSIONS
  These results suggest that PGN_0274 and PGN_1740 play a key role in biofilm formation by P. gingivalis.
authors.forename: Satosu
authors.initials: S
authors.lastname: Onozawa
authors.affiliation: Oral Health Science Center, Tokyo Dental College, 2-9-18, Misaki-cho, Chiyoda-ku, Tokyo, Japan. yukikuchi@tdc.ac.jp.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: Kazuko
authors.initials: K
authors.lastname: Shibayama
authors.forename: Eitoyo
authors.initials: E
authors.lastname: Kokubu
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakayama
authors.forename: Tetsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakano
authors.forename: Yukinaga
authors.initials: Y
authors.lastname: Shibata
authors.forename: Naoya
authors.initials: N
authors.lastname: Ohara
authors.forename: Koji
authors.initials: K
authors.lastname: Nakayama
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ishihara
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kawakami
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Hasegawa
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001431:Bacteriological Techniques; D018441:Biofilms / Q000254:growth & development; D004396:Coloring Agents; D004268:DNA-Binding Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D017353:Gene Deletion; D005840:Gentian Violet; D006801:Humans; D008780:Methyltransferases / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009391:Nephelometry and Turbidimetry / Q000379:methods; D016966:Porphyromonas gingivalis / Q000254:growth & development / Q000502:physiology*; D012808:Sigma Factor / Q000235:genetics / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D004396:Coloring Agents; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; D005840:Gentian Violet