Microbial Geography of the Oral Cavity. human oral metagenome

We aimed to determine the bacterial diversity of different oral micro-niches and assess whether saliva and plaque samples are representative of oral microbial composition. We have minutely taken samples from each surface of individual teeth and gingival crevices from two healthy volunteers (112 samples per donor), as well as samples from the tongue dorsum, non-stimulated and stimulated saliva. DNA was extracted from each sample and the 16S rRNA gene was amplified by PCR and pyrosequenced to obtain on overage over 2,700 reads per sample, which were taxonomically assigned to obtain a geographic map of bacterial diversity at each tooth and sulcus location. The data show considerable differences in bacterial composition between teeth at different intra-oral locations and between surfaces of the same tooth. The most pronounced differences were observed in incisors and canines, where genera like Streptococcus were found at 40-70% on the vestibular (buccal) surface but were almost absent on the palatine (lingual) sides. Saliva samples, especially non-stimulated saliva, were not representative of supra- and subgingival plaque. We suggest that more precise sampling is required to properly determine oral microbial composition and to relate that diversity with epidemiological, clinical and etiological parameters.