title: Extracellular deoxyribonuclease production by periodontal bacteria.
abstract: OBJECTIVE
  Whilst certain bacteria have long been known to secrete extracellular deoxyribonuclease (DNase), the purpose in microbial physiology was unclear. Recently, however, this enzyme has been demonstrated to confer enhanced virulence, enabling bacteria to evade the host's immune defence of extruded DNA/chromatin filaments, termed neutrophil extracellular traps (NETs). As NETs have recently been identified in infected periodontal tissue, the aim of this study was to screen periodontal bacteria for extracellular DNase activity.
  
  
  METHODS
  To determine whether DNase activity was membrane bound or secreted, 34 periodontal bacteria were cultured in broth and on agar plates. Pelleted bacteria and supernatants from broth cultures were analysed for their ability to degrade DNA, with relative activity levels determined using an agarose gel electrophoresis assay. Following culture on DNA-supplemented agar, expression was determined by the presence of a zone of hydrolysis and DNase activity related to colony size.
  
  
  RESULTS
  Twenty-seven bacteria, including red and orange complex members Porphyromonas gingivalis, Tannerella forsythia, Fusobacterium nucleatum, Parvimonas micra, Prevotella intermedia, Streptococcus constellatus, Campylobacter rectus and Prevotella nigrescens, were observed to express extracellular DNase activity. Differences in DNase activity were noted, however, when bacteria were assayed in different culture states. Analysis of the activity of secreted DNase from bacterial broth cultures confirmed their ability to degrade NETs.
  
  
  CONCLUSIONS
  The present study demonstrates, for the first time, that DNase activity is a relatively common property of bacteria associated with advanced periodontal disease. Further work is required to determine the importance of this bacterial DNase activity in the pathogenesis of periodontitis.
authors.affiliation: Department of Periodontology, School of Dentistry, University of Birmingham, Birmingham, UK.
authors.forename: L J
authors.initials: LJ
authors.lastname: Palmer
authors.forename: I L C
authors.initials: IL
authors.lastname: Chapple
authors.forename: H J
authors.initials: HJ
authors.lastname: Wright
authors.forename: A
authors.initials: A
authors.lastname: Roberts
authors.forename: P R
authors.initials: PR
authors.lastname: Cooper
mesh_terms: D001421:Bacteria, Anaerobic / Q000201:enzymology* / Q000472:pathogenicity; D001426:Bacterial Proteins / Q000378:metabolism*; D001439:Bacteroides / Q000201:enzymology / Q000472:pathogenicity; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism*; D004587:Electrophoresis, Agar Gel; D006801:Humans; D006868:Hydrolysis; D057131:Immune Evasion / Q000502:physiology*; D009504:Neutrophils / Q000378:metabolism*; D010518:Periodontitis / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000201:enzymology / Q000472:pathogenicity; D013291:Streptococcus / Q000201:enzymology / Q000472:pathogenicity; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D002843:Chromatin; D004247:DNA; D003851:Deoxyribonucleases