title: Strains of Enterococcus faecalis differ in their ability to coexist in biofilms with other root canal bacteria.
abstract: OBJECTIVE
  To investigate the relationship between protease production and the ability of Enterococcus faecalis strains to coexist in biofilms with other bacteria commonly recovered from infected root canals.
  
  
  METHODS
  Biofilms with bacteria in mono-, dual- and four-species communities were developed in flow chambers. The organisms used were Lactobacillus salivarius, Streptococcus gordonii and Actinomyces naeslundii and E. faecalis strains, GUL1 and OG1RF. Biovolume and species distribution were examined using 16S rRNA fluorescence in situ hybridization in combination with confocal microscopy and image analysis. The full proteome of the E. faecalis strains was studied using two-dimensional gel electrophoresis. Spots of interest were identified using tandem mass spectroscopy and quantified using Delta 2D software.
  
  
  RESULTS
  All bacteria formed biofilms and an anova analysis revealed that the biofilm biomass increased significantly (P ≤ 0.01) between 6 and 24 h. L. salivarius, S. gordonii and A. naeslundii formed mutualistic biofilm communities, and this pattern was unchanged when E. faecalis GUL1 was included in the consortium. However, with OG1RF, L. salivarius and S. gordonii were outcompeted in a 24-h biofilm. Proteomic analysis revealed that OG1RF secreted higher levels of proteases, GelE (P = 0.02) and SprE (P = 0.002) and a previously unidentified serine protease (P = 0.05), than GUL1.
  
  
  CONCLUSIONS
  Different strains of E. faecalis can interact synergistically or antagonistically with a consortium of root canal bacteria. A possible mechanism underlying this, as well as potential differences in virulence, is production of different levels of proteases, which can cause detachment of neighbouring bacteria and tissue damage.
authors.affiliation: Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden.
authors.forename: L E
authors.initials: LE
authors.lastname: Chávez de Paz
authors.affiliation: Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden.
authors.forename: J R
authors.initials: JR
authors.lastname: Davies
authors.affiliation: Department of Endodontology, The Sahlgrenska Academy at Gothenburg University, Gothenburg, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Bergenholtz
authors.affiliation: Department of Oral Biology, Faculty of Odontology, Malmö University, Malmö, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Svensäter
mesh_terms: D000190:Actinomyces / Q000302:isolation & purification / Q000502:physiology*; D001431:Bacteriological Techniques; D018441:Biofilms / Q000145:classification* / Q000254:growth & development; D018533:Biomass; D003786:Dental Pulp Cavity / Q000382:microbiology*; D015180:Electrophoresis, Gel, Two-Dimensional; D013293:Enterococcus faecalis / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D000069996:Ligilactobacillus salivarius / Q000302:isolation & purification / Q000502:physiology*; D059013:Microbial Consortia / Q000502:physiology*; D018613:Microscopy, Confocal; D040901:Proteomics; D012336:RNA, Ribosomal, 16S; D012390:Root Canal Therapy; D054773:Streptococcus gordonii / Q000302:isolation & purification / Q000502:physiology*; D053719:Tandem Mass Spectrometry; D014774:Virulence
chemical_list: D012336:RNA, Ribosomal, 16S
keywords: antagonism; apical periodontitis; bacterial consortium; multispecies; mutualism