title: Exploring bacterial diversity of endodontic microbiota by cloning and sequencing 16S rRNA.
abstract: BACKGROUND
  The characterization of microbial communities infecting the endodontic system in each clinical condition may help on the establishment of a correct prognosis and distinct strategies of treatment. The purpose of this study was to determine the bacterial diversity in primary endodontic infections by 16S ribosomal-RNA (rRNA) sequence analysis.
  
  
  METHODS
  Samples from root canals of untreated asymptomatic teeth (n = 12) exhibiting periapical lesions were obtained, 16S rRNA bacterial genomic libraries were constructed and sequenced, and bacterial diversity was estimated.
  
  
  RESULTS
  A total of 489 clones were analyzed (mean, 40.7 ± 8.0 clones per sample). Seventy phylotypes were identified of which six were novel phylotypes belonging to the family Ruminococcaceae. The mean number of taxa per canal was 10.0, ranging from 3 to 21 per sample; 65.7% of the cloned sequences represented phylotypes for which no cultivated isolates have been reported. The most prevalent taxa were Atopobium rimae (50.0%), Dialister invisus, Prevotella oris, Pseudoramibacter alactolyticus, and Tannerella forsythia (33.3%).
  
  
  CONCLUSIONS
  Although several key species predominate in endodontic samples of asymptomatic cases with periapical lesions, the primary endodontic infection is characterized by a wide bacterial diversity, which is mostly represented by members of the phylum Firmicutes belonging to the class Clostridia followed by the phylum Bacteroidetes.
authors.affiliation: Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Ribeiro
authors.forename: Flávia
authors.initials: F
authors.lastname: Matarazzo
authors.forename: Marcelo
authors.initials: M
authors.lastname: Faveri
authors.forename: Denise M
authors.initials: DM
authors.lastname: Zezell
authors.forename: Marcia P A
authors.initials: MP
authors.lastname: Mayer
mesh_terms: D000293:Adolescent; D000328:Adult; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D041963:Bacteroidetes / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D003013:Clostridium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D003786:Dental Pulp Cavity / Q000382:microbiology*; D015698:Genomic Library; D006801:Humans; D059013:Microbial Consortia / Q000235:genetics; D008875:Middle Aged; D010483:Periapical Diseases / Q000382:microbiology*; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics*; D045857:Ruminococcus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D017423:Sequence Analysis, RNA / Q000379:methods; D055815:Young Adult
chemical_list: D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S